EVP_ENCRYPTINIT(3ossl) OpenSSL EVP_ENCRYPTINIT(3ossl)
NAME
EVP_CIPHER_fetch, EVP_CIPHER_up_ref, EVP_CIPHER_free, EVP_CIPHER_CTX_new,
EVP_CIPHER_CTX_reset, EVP_CIPHER_CTX_free, EVP_CIPHER_CTX_dup,
EVP_CIPHER_CTX_copy, EVP_EncryptInit_ex, EVP_EncryptInit_ex2,
EVP_EncryptUpdate, EVP_EncryptFinal_ex, EVP_DecryptInit_ex,
EVP_DecryptInit_ex2, EVP_DecryptUpdate, EVP_DecryptFinal_ex,
EVP_CipherInit_ex, EVP_CipherInit_ex2, EVP_CipherInit_SKEY,
EVP_CipherUpdate, EVP_CipherFinal_ex, EVP_CIPHER_CTX_set_key_length,
EVP_CIPHER_CTX_ctrl, EVP_EncryptInit, EVP_EncryptFinal, EVP_DecryptInit,
EVP_DecryptFinal, EVP_CipherInit, EVP_CipherFinal, EVP_Cipher,
EVP_CIPHER_can_pipeline, EVP_CipherPipelineEncryptInit,
EVP_CipherPipelineDecryptInit, EVP_CipherPipelineUpdate,
EVP_CipherPipelineFinal, EVP_get_cipherbyname, EVP_get_cipherbynid,
EVP_get_cipherbyobj, EVP_CIPHER_is_a, EVP_CIPHER_get0_name,
EVP_CIPHER_get0_description, EVP_CIPHER_names_do_all,
EVP_CIPHER_get0_provider, EVP_CIPHER_get_nid, EVP_CIPHER_get_params,
EVP_CIPHER_gettable_params, EVP_CIPHER_get_block_size,
EVP_CIPHER_get_key_length, EVP_CIPHER_get_iv_length,
EVP_CIPHER_get_flags, EVP_CIPHER_get_mode, EVP_CIPHER_get_type,
EVP_CIPHER_CTX_cipher, EVP_CIPHER_CTX_get0_cipher,
EVP_CIPHER_CTX_get1_cipher, EVP_CIPHER_CTX_get0_name,
EVP_CIPHER_CTX_get_nid, EVP_CIPHER_CTX_get_params,
EVP_CIPHER_gettable_ctx_params, EVP_CIPHER_CTX_gettable_params,
EVP_CIPHER_CTX_set_params, EVP_CIPHER_settable_ctx_params,
EVP_CIPHER_CTX_settable_params, EVP_CIPHER_CTX_get_block_size,
EVP_CIPHER_CTX_get_key_length, EVP_CIPHER_CTX_get_iv_length,
EVP_CIPHER_CTX_get_tag_length, EVP_CIPHER_CTX_flags,
EVP_CIPHER_CTX_set_flags, EVP_CIPHER_CTX_clear_flags,
EVP_CIPHER_CTX_test_flags, EVP_CIPHER_CTX_get_type,
EVP_CIPHER_CTX_get_mode, EVP_CIPHER_CTX_get_num, EVP_CIPHER_CTX_set_num,
EVP_CIPHER_CTX_is_encrypting, EVP_CIPHER_param_to_asn1,
EVP_CIPHER_asn1_to_param, EVP_CIPHER_CTX_set_padding, EVP_enc_null,
EVP_CIPHER_do_all_provided, EVP_CIPHER_nid, EVP_CIPHER_name,
EVP_CIPHER_block_size, EVP_CIPHER_key_length, EVP_CIPHER_iv_length,
EVP_CIPHER_flags, EVP_CIPHER_mode, EVP_CIPHER_type,
EVP_CIPHER_CTX_encrypting, EVP_CIPHER_CTX_nid, EVP_CIPHER_CTX_block_size,
EVP_CIPHER_CTX_key_length, EVP_CIPHER_CTX_iv_length,
EVP_CIPHER_CTX_tag_length, EVP_CIPHER_CTX_num, EVP_CIPHER_CTX_type,
EVP_CIPHER_CTX_mode - EVP cipher routines
SYNOPSIS
#include <openssl/evp.h>
EVP_CIPHER *EVP_CIPHER_fetch(OSSL_LIB_CTX *ctx, const char *algorithm,
const char *properties);
int EVP_CIPHER_up_ref(EVP_CIPHER *cipher);
void EVP_CIPHER_free(EVP_CIPHER *cipher);
EVP_CIPHER_CTX *EVP_CIPHER_CTX_new(void);
int EVP_CIPHER_CTX_reset(EVP_CIPHER_CTX *ctx);
void EVP_CIPHER_CTX_free(EVP_CIPHER_CTX *ctx);
EVP_CIPHER_CTX *EVP_CIPHER_CTX_dup(const EVP_CIPHER_CTX *in);
int EVP_CIPHER_CTX_copy(EVP_CIPHER_CTX *out, const EVP_CIPHER_CTX *in);
int EVP_EncryptInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
ENGINE *impl, const unsigned char *key, const unsigned char *iv);
int EVP_EncryptInit_ex2(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
const unsigned char *key, const unsigned char *iv,
const OSSL_PARAM params[]);
int EVP_EncryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
int *outl, const unsigned char *in, int inl);
int EVP_EncryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl);
int EVP_DecryptInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
ENGINE *impl, const unsigned char *key, const unsigned char *iv);
int EVP_DecryptInit_ex2(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
const unsigned char *key, const unsigned char *iv,
const OSSL_PARAM params[]);
int EVP_DecryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
int *outl, const unsigned char *in, int inl);
int EVP_DecryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl);
int EVP_CipherInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
ENGINE *impl, const unsigned char *key, const unsigned char *iv, int enc);
int EVP_CipherInit_ex2(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
const unsigned char *key, const unsigned char *iv,
int enc, const OSSL_PARAM params[]);
int EVP_CipherInit_SKEY(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *cipher,
EVP_SKEY *skey, const unsigned char *iv, size_t iv_len,
int enc, const OSSL_PARAM params[]);
int EVP_CipherUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
int *outl, const unsigned char *in, int inl);
int EVP_CipherFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl);
int EVP_EncryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
const unsigned char *key, const unsigned char *iv);
int EVP_EncryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl);
int EVP_DecryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
const unsigned char *key, const unsigned char *iv);
int EVP_DecryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl);
int EVP_CipherInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
const unsigned char *key, const unsigned char *iv, int enc);
int EVP_CipherFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl);
int EVP_Cipher(EVP_CIPHER_CTX *ctx, unsigned char *out,
const unsigned char *in, unsigned int inl);
int EVP_CIPHER_can_pipeline(const EVP_CIPHER *cipher, int enc);
int EVP_CipherPipelineEncryptInit(EVP_CIPHER_CTX *ctx,
const EVP_CIPHER *cipher,
const unsigned char *key, size_t keylen,
size_t numpipes,
const unsigned char **iv, size_t ivlen);
int EVP_CipherPipelineDecryptInit(EVP_CIPHER_CTX *ctx,
const EVP_CIPHER *cipher,
const unsigned char *key, size_t keylen,
size_t numpipes,
const unsigned char **iv, size_t ivlen);
int EVP_CipherPipelineUpdate(EVP_CIPHER_CTX *ctx,
unsigned char **out, size_t *outl,
const size_t *outsize,
const unsigned char **in, const size_t *inl);
int EVP_CipherPipelineFinal(EVP_CIPHER_CTX *ctx,
unsigned char **outm, size_t *outl,
const size_t *outsize);
int EVP_CIPHER_CTX_set_padding(EVP_CIPHER_CTX *x, int padding);
int EVP_CIPHER_CTX_set_key_length(EVP_CIPHER_CTX *x, int keylen);
int EVP_CIPHER_CTX_ctrl(EVP_CIPHER_CTX *ctx, int cmd, int p1, void *p2);
int EVP_CIPHER_CTX_rand_key(EVP_CIPHER_CTX *ctx, unsigned char *key);
void EVP_CIPHER_CTX_set_flags(EVP_CIPHER_CTX *ctx, int flags);
void EVP_CIPHER_CTX_clear_flags(EVP_CIPHER_CTX *ctx, int flags);
int EVP_CIPHER_CTX_test_flags(const EVP_CIPHER_CTX *ctx, int flags);
const EVP_CIPHER *EVP_get_cipherbyname(const char *name);
const EVP_CIPHER *EVP_get_cipherbynid(int nid);
const EVP_CIPHER *EVP_get_cipherbyobj(const ASN1_OBJECT *a);
int EVP_CIPHER_get_nid(const EVP_CIPHER *e);
int EVP_CIPHER_is_a(const EVP_CIPHER *cipher, const char *name);
int EVP_CIPHER_names_do_all(const EVP_CIPHER *cipher,
void (*fn)(const char *name, void *data),
void *data);
const char *EVP_CIPHER_get0_name(const EVP_CIPHER *cipher);
const char *EVP_CIPHER_get0_description(const EVP_CIPHER *cipher);
const OSSL_PROVIDER *EVP_CIPHER_get0_provider(const EVP_CIPHER *cipher);
int EVP_CIPHER_get_block_size(const EVP_CIPHER *e);
int EVP_CIPHER_get_key_length(const EVP_CIPHER *e);
int EVP_CIPHER_get_iv_length(const EVP_CIPHER *e);
unsigned long EVP_CIPHER_get_flags(const EVP_CIPHER *e);
unsigned long EVP_CIPHER_get_mode(const EVP_CIPHER *e);
int EVP_CIPHER_get_type(const EVP_CIPHER *cipher);
const EVP_CIPHER *EVP_CIPHER_CTX_get0_cipher(const EVP_CIPHER_CTX *ctx);
EVP_CIPHER *EVP_CIPHER_CTX_get1_cipher(const EVP_CIPHER_CTX *ctx);
int EVP_CIPHER_CTX_get_nid(const EVP_CIPHER_CTX *ctx);
const char *EVP_CIPHER_CTX_get0_name(const EVP_CIPHER_CTX *ctx);
int EVP_CIPHER_get_params(EVP_CIPHER *cipher, OSSL_PARAM params[]);
int EVP_CIPHER_CTX_set_params(EVP_CIPHER_CTX *ctx, const OSSL_PARAM params[]);
int EVP_CIPHER_CTX_get_params(EVP_CIPHER_CTX *ctx, OSSL_PARAM params[]);
const OSSL_PARAM *EVP_CIPHER_gettable_params(const EVP_CIPHER *cipher);
const OSSL_PARAM *EVP_CIPHER_settable_ctx_params(const EVP_CIPHER *cipher);
const OSSL_PARAM *EVP_CIPHER_gettable_ctx_params(const EVP_CIPHER *cipher);
const OSSL_PARAM *EVP_CIPHER_CTX_settable_params(EVP_CIPHER_CTX *ctx);
const OSSL_PARAM *EVP_CIPHER_CTX_gettable_params(EVP_CIPHER_CTX *ctx);
int EVP_CIPHER_CTX_get_block_size(const EVP_CIPHER_CTX *ctx);
int EVP_CIPHER_CTX_get_key_length(const EVP_CIPHER_CTX *ctx);
int EVP_CIPHER_CTX_get_iv_length(const EVP_CIPHER_CTX *ctx);
int EVP_CIPHER_CTX_get_tag_length(const EVP_CIPHER_CTX *ctx);
int EVP_CIPHER_CTX_get_type(const EVP_CIPHER_CTX *ctx);
int EVP_CIPHER_CTX_get_mode(const EVP_CIPHER_CTX *ctx);
int EVP_CIPHER_CTX_get_num(const EVP_CIPHER_CTX *ctx);
int EVP_CIPHER_CTX_set_num(EVP_CIPHER_CTX *ctx, int num);
int EVP_CIPHER_CTX_is_encrypting(const EVP_CIPHER_CTX *ctx);
int EVP_CIPHER_param_to_asn1(EVP_CIPHER_CTX *c, ASN1_TYPE *type);
int EVP_CIPHER_asn1_to_param(EVP_CIPHER_CTX *c, ASN1_TYPE *type);
void EVP_CIPHER_do_all_provided(OSSL_LIB_CTX *libctx,
void (*fn)(EVP_CIPHER *cipher, void *arg),
void *arg);
#define EVP_CIPHER_nid EVP_CIPHER_get_nid
#define EVP_CIPHER_name EVP_CIPHER_get0_name
#define EVP_CIPHER_block_size EVP_CIPHER_get_block_size
#define EVP_CIPHER_key_length EVP_CIPHER_get_key_length
#define EVP_CIPHER_iv_length EVP_CIPHER_get_iv_length
#define EVP_CIPHER_flags EVP_CIPHER_get_flags
#define EVP_CIPHER_mode EVP_CIPHER_get_mode
#define EVP_CIPHER_type EVP_CIPHER_get_type
#define EVP_CIPHER_CTX_encrypting EVP_CIPHER_CTX_is_encrypting
#define EVP_CIPHER_CTX_nid EVP_CIPHER_CTX_get_nid
#define EVP_CIPHER_CTX_block_size EVP_CIPHER_CTX_get_block_size
#define EVP_CIPHER_CTX_key_length EVP_CIPHER_CTX_get_key_length
#define EVP_CIPHER_CTX_iv_length EVP_CIPHER_CTX_get_iv_length
#define EVP_CIPHER_CTX_tag_length EVP_CIPHER_CTX_get_tag_length
#define EVP_CIPHER_CTX_num EVP_CIPHER_CTX_get_num
#define EVP_CIPHER_CTX_type EVP_CIPHER_CTX_get_type
#define EVP_CIPHER_CTX_mode EVP_CIPHER_CTX_get_mode
The following function has been deprecated since OpenSSL 3.0, and can be
hidden entirely by defining OPENSSL_API_COMPAT with a suitable version
value, see openssl_user_macros(7):
const EVP_CIPHER *EVP_CIPHER_CTX_cipher(const EVP_CIPHER_CTX *ctx);
The following function has been deprecated since OpenSSL 1.1.0, and can
be hidden entirely by defining OPENSSL_API_COMPAT with a suitable version
value, see openssl_user_macros(7):
int EVP_CIPHER_CTX_flags(const EVP_CIPHER_CTX *ctx);
DESCRIPTION
The EVP cipher routines are a high-level interface to certain symmetric
ciphers.
The EVP_CIPHER type is a structure for cipher method implementation.
EVP_CIPHER_fetch()
Fetches the cipher implementation for the given algorithm from any
provider offering it, within the criteria given by the properties.
See "ALGORITHM FETCHING" in crypto(7) for further information.
The returned value must eventually be freed with EVP_CIPHER_free().
Fetched EVP_CIPHER structures are reference counted.
EVP_CIPHER_up_ref()
Increments the reference count for an EVP_CIPHER structure.
EVP_CIPHER_free()
Decrements the reference count for the fetched EVP_CIPHER structure.
If the reference count drops to 0 then the structure is freed. If
the argument is NULL, nothing is done.
EVP_CIPHER_CTX_new()
Allocates and returns a cipher context.
EVP_CIPHER_CTX_free()
Clears all information from a cipher context and frees any allocated
memory associated with it, including ctx itself. This function should
be called after all operations using a cipher are complete so
sensitive information does not remain in memory. If the argument is
NULL, nothing is done.
EVP_CIPHER_CTX_dup()
Can be used to duplicate the cipher state from in. This is useful to
avoid multiple EVP_CIPHER_fetch() calls or if large amounts of data
are to be fed which only differ in the last few bytes.
EVP_CIPHER_CTX_copy()
Can be used to copy the cipher state from in to out.
EVP_CIPHER_CTX_ctrl()
This is a legacy method. EVP_CIPHER_CTX_set_params() and
EVP_CIPHER_CTX_get_params() is the mechanism that should be used to
set and get parameters that are used by providers.
Performs cipher-specific control actions on context ctx. The control
command is indicated in cmd and any additional arguments in p1 and
p2. EVP_CIPHER_CTX_ctrl() must be called after EVP_CipherInit_ex2().
Other restrictions may apply depending on the control type and cipher
implementation.
If this function happens to be used with a fetched EVP_CIPHER, it
will translate the controls that are known to OpenSSL into
OSSL_PARAM(3) parameters with keys defined by OpenSSL and call
EVP_CIPHER_CTX_get_params() or EVP_CIPHER_CTX_set_params() as is
appropriate for each control command.
See "CONTROLS" below for more information, including what
translations are being done.
EVP_CIPHER_get_params()
Retrieves the requested list of algorithm params from a CIPHER
cipher. See "PARAMETERS" below for more information.
EVP_CIPHER_CTX_get_params()
Retrieves the requested list of params from CIPHER context ctx. See
"PARAMETERS" below for more information.
EVP_CIPHER_CTX_set_params()
Sets the list of params into a CIPHER context ctx. See "PARAMETERS"
below for more information.
EVP_CIPHER_gettable_params()
Get a constant OSSL_PARAM(3) array that describes the retrievable
parameters that can be used with EVP_CIPHER_get_params().
EVP_CIPHER_gettable_ctx_params() and EVP_CIPHER_CTX_gettable_params()
Get a constant OSSL_PARAM(3) array that describes the retrievable
parameters that can be used with EVP_CIPHER_CTX_get_params().
EVP_CIPHER_gettable_ctx_params() returns the parameters that can be
retrieved from the algorithm, whereas
EVP_CIPHER_CTX_gettable_params() returns the parameters that can be
retrieved in the context's current state.
EVP_CIPHER_settable_ctx_params() and EVP_CIPHER_CTX_settable_params()
Get a constant OSSL_PARAM(3) array that describes the settable
parameters that can be used with EVP_CIPHER_CTX_set_params().
EVP_CIPHER_settable_ctx_params() returns the parameters that can be
set from the algorithm, whereas EVP_CIPHER_CTX_settable_params()
returns the parameters that can be set in the context's current
state.
EVP_EncryptInit_ex2()
Sets up cipher context ctx for encryption with cipher type. ctx MUST
NOT be NULL. type is typically supplied by calling
EVP_CIPHER_fetch(). type may also be set using legacy functions such
as EVP_aes_256_cbc(), but this is not recommended for new
applications. key is the symmetric key to use and iv is the IV to use
(if necessary), the actual number of bytes used for the key and IV
depends on the cipher. The parameters params will be set on the
context after initialisation. It is possible to set all parameters to
NULL except type in an initial call and supply the remaining
parameters in subsequent calls, all of which have type set to NULL.
This is done when the default cipher parameters are not appropriate.
For EVP_CIPH_GCM_MODE the IV will be generated internally if it is
not specified.
EVP_EncryptInit_ex()
This legacy function is similar to EVP_EncryptInit_ex2() when impl is
NULL. The implementation of the type from the impl engine will be
used if it exists.
EVP_EncryptUpdate()
Encrypts inl bytes from the buffer in and writes the encrypted
version to out. The pointers out and in may point to the same
location, in which case the encryption will be done in-place.
However, in-place encryption is guaranteed to work only if the
encryption context (ctx) has processed data in multiples of the block
size. If the context contains an incomplete data block from previous
operations, in-place encryption will fail. ctx MUST NOT be NULL.
If out and in point to different locations, the two buffers must be
disjoint, otherwise the operation might fail or the outcome might be
undefined.
This function can be called multiple times to encrypt successive
blocks of data. The amount of data written depends on the block
alignment of the encrypted data. For most ciphers and modes, the
amount of data written can be anything from zero bytes to (inl +
cipher_block_size - 1) bytes. For wrap cipher modes, the amount of
data written can be anything from zero bytes to (inl rounded up to
cipher_block_size + cipher_block_size) bytes. For stream ciphers,
the amount of data written can be anything from zero bytes to inl
bytes. Thus, the buffer pointed to by out must contain sufficient
room for the operation being performed. The actual number of bytes
written is placed in outl.
If padding is enabled (the default) then EVP_EncryptFinal_ex()
encrypts the "final" data, that is any data that remains in a partial
block. It uses standard block padding (aka PKCS padding) as
described in the NOTES section, below. The encrypted final data is
written to out which should have sufficient space for one cipher
block. The number of bytes written is placed in outl. After this
function is called the encryption operation is finished and no
further calls to EVP_EncryptUpdate() should be made.
If padding is disabled then EVP_EncryptFinal_ex() will not encrypt
any more data and it will return an error if any data remains in a
partial block: that is if the total data length is not a multiple of
the block size.
EVP_DecryptInit_ex2(), EVP_DecryptInit_ex(), EVP_DecryptUpdate() and
EVP_DecryptFinal_ex()
These functions are the corresponding decryption operations.
EVP_DecryptFinal() will return an error code if padding is enabled
and the final block is not correctly formatted. The parameters and
restrictions are identical to the encryption operations. ctx MUST NOT
be NULL.
EVP_CipherInit_ex2(), EVP_CipherInit_ex(), EVP_CipherUpdate() and
EVP_CipherFinal_ex()
These functions can be used for decryption or encryption. The
operation performed depends on the value of the enc parameter. It
should be set to 1 for encryption, 0 for decryption and -1 to leave
the value unchanged (the actual value of 'enc' being supplied in a
previous call).
EVP_CipherInit_SKEY()
This function is similar to EVP_CipherInit_ex2() but accepts a
symmetric key object of type EVP_SKEY as a key.
EVP_CIPHER_CTX_reset()
Clears all information from a cipher context and free up any
allocated memory associated with it, except the ctx itself. This
function should be called anytime ctx is reused by another
EVP_CipherInit() / EVP_CipherUpdate() / EVP_CipherFinal() series of
calls.
EVP_EncryptInit(3), EVP_DecryptInit() and EVP_CipherInit()
Behave in a similar way to EVP_EncryptInit_ex(), EVP_DecryptInit_ex()
and EVP_CipherInit_ex() except if the type is not a fetched cipher
they use the default implementation of the type.
EVP_EncryptFinal(), EVP_DecryptFinal() and EVP_CipherFinal()
Identical to EVP_EncryptFinal_ex(), EVP_DecryptFinal_ex() and
EVP_CipherFinal_ex(). In previous releases they also cleaned up the
ctx, but this is no longer done and EVP_CIPHER_CTX_cleanup() must be
called to free any context resources.
EVP_Cipher()
Encrypts or decrypts a maximum inl amount of bytes from in and leaves
the result in out.
For legacy ciphers - If the cipher doesn't have the flag
EVP_CIPH_FLAG_CUSTOM_CIPHER set, then inl must be a multiple of
EVP_CIPHER_get_block_size(). If it isn't, the result is undefined.
If the cipher has that flag set, then inl can be any size.
Due to the constraints of the API contract of this function it
shouldn't be used in applications, please consider using
EVP_CipherUpdate() and EVP_CipherFinal_ex() instead.
EVP_CIPHER_can_pipeline()
This function checks if a EVP_CIPHER fetched using EVP_CIPHER_fetch()
supports cipher pipelining. If the cipher supports pipelining, it
returns 1, otherwise 0. This function will return 0 for non-fetched
ciphers such as EVP_aes_128_gcm(). There are currently no built-in
ciphers that support pipelining.
Cipher pipelining support allows an application to submit multiple
chunks of data in one set of EVP_CipherUpdate()/EVP_CipherFinal
calls, thereby allowing the provided implementation to take advantage
of parallel computing. This is beneficial for hardware accelerators
as pipeline amortizes the latency over multiple chunks.
For non-fetched ciphers, EVP_CipherPipelineEncryptInit() or
EVP_CipherPipelineDecryptInit() may be directly called, which will
perform a fetch and return an error if a pipeline supported
implementation is not found.
EVP_CipherPipelineEncryptInit(), EVP_CipherPipelineDecryptInit(),
EVP_CipherPipelineUpdate() and EVP_CipherPipelineFinal()
These functions can be used to perform multiple encryption or
decryption operations in parallel. EVP_CIPHER_can_pipeline() may be
called to check if the cipher supports pipelining. These functions
are analogous to EVP_EncryptInit_ex2(), EVP_DecryptInit_ex2(),
EVP_CipherUpdate() and EVP_CipherFinal() but take an array of
pointers for iv, input and output buffers.
The key, of length keylen, is the symmetric key to use. The numpipes
parameter specifies the number of parallel operations to perform. The
numpipes cannot exceed EVP_MAX_PIPES. The iv parameter is an array of
buffer pointers, containing IVs. The array size must be equal to
numpipes. The size of each IV buffer must be equal to ivlen. When IV
is not provided, iv must be NULL, rather than an array of NULL
pointers. The in parameters takes an array of buffer pointers, each
pointing to a buffer containing the input data. The buffers can be of
different sizes. The inl parameter is an array of size_t, each
specifying the size of the corresponding input buffer. The out and
outm parameters are arrays of buffer pointers, each pointing to a
buffer where the output data will be written. The outsize parameter
is an array of size_t, each specifying the size of the corresponding
output buffer. The outl parameter is an array of size_t which will be
updated with the size of the output data written to the corresponding
output buffer. For size requirement of the output buffers, see the
description of EVP_CipherUpdate().
The EVP_CipherPipelineUpdate() function can be called multiple times
to encrypt successive blocks of data. For AAD data, the out, and
outsize parameter should be NULL, rather than an array of NULL
pointers.
EVP_get_cipherbyname(), EVP_get_cipherbynid() and EVP_get_cipherbyobj()
Returns an EVP_CIPHER structure when passed a cipher name, a cipher
NID or an ASN1_OBJECT structure respectively.
EVP_get_cipherbyname() will return NULL for algorithms such as
"AES-128-SIV", "AES-128-CBC-CTS" and "CAMELLIA-128-CBC-CTS" which
were previously only accessible via low level interfaces.
The EVP_get_cipherbyname() function is present for backwards
compatibility with OpenSSL prior to version 3 and is different to the
EVP_CIPHER_fetch() function since it does not attempt to "fetch" an
implementation of the cipher. Additionally, it only knows about
ciphers that are built-in to OpenSSL and have an associated NID.
Similarly EVP_get_cipherbynid() and EVP_get_cipherbyobj() also return
objects without an associated implementation.
When the cipher objects returned by these functions are used (such as
in a call to EVP_EncryptInit_ex()) an implementation of the cipher
will be implicitly fetched from the loaded providers. This fetch
could fail if no suitable implementation is available. Use
EVP_CIPHER_fetch() instead to explicitly fetch the algorithm and an
associated implementation from a provider.
See "ALGORITHM FETCHING" in crypto(7) for more information about
fetching.
The cipher objects returned from these functions do not need to be
freed with EVP_CIPHER_free().
EVP_CIPHER_get_nid() and EVP_CIPHER_CTX_get_nid()
Return the NID of a cipher when passed an EVP_CIPHER or
EVP_CIPHER_CTX structure. The actual NID value is an internal value
which may not have a corresponding OBJECT IDENTIFIER. NID_undef is
returned in the event that the nid is unknown or if the cipher has
not been properly initialized via a call to EVP_CipherInit.
EVP_CIPHER_CTX_set_flags(), EVP_CIPHER_CTX_clear_flags() and
EVP_CIPHER_CTX_test_flags()
Sets, clears and tests ctx flags. See "FLAGS" below for more
information.
For provided ciphers EVP_CIPHER_CTX_set_flags() should be called only
after the fetched cipher has been assigned to the ctx. It is
recommended to use "PARAMETERS" instead.
EVP_CIPHER_CTX_set_padding()
Enables or disables padding. This function should be called after the
context is set up for encryption or decryption with
EVP_EncryptInit_ex2(), EVP_DecryptInit_ex2(), EVP_CipherInit_ex2(),
or EVP_CipherInit_SKEY(). By default encryption operations are padded
using standard block padding and the padding is checked and removed
when decrypting. If the pad parameter is zero then no padding is
performed, the total amount of data encrypted or decrypted must then
be a multiple of the block size or an error will occur. x MUST NOT be
NULL.
EVP_CIPHER_get_key_length() and EVP_CIPHER_CTX_get_key_length()
Return the key length of a cipher when passed an EVP_CIPHER or
EVP_CIPHER_CTX structure. The constant EVP_MAX_KEY_LENGTH is the
maximum key length for all ciphers. Note: although
EVP_CIPHER_get_key_length() is fixed for a given cipher, the value of
EVP_CIPHER_CTX_get_key_length() may be different for variable key
length ciphers.
EVP_CIPHER_CTX_set_key_length()
Sets the key length of the cipher context. If the cipher is a fixed
length cipher then attempting to set the key length to any value
other than the fixed value is an error.
EVP_CIPHER_get_iv_length() and EVP_CIPHER_CTX_get_iv_length()
Return the IV length of a cipher when passed an EVP_CIPHER or
EVP_CIPHER_CTX. It will return zero if the cipher does not use an IV,
if the cipher has not yet been initialized within the EVP_CIPHER_CTX,
or if the passed cipher is NULL. The constant EVP_MAX_IV_LENGTH is
the maximum IV length for all ciphers.
EVP_CIPHER_CTX_get_tag_length()
Returns the tag length of an AEAD cipher when passed a
EVP_CIPHER_CTX. It will return zero if the cipher does not support a
tag. It returns a default value if the tag length has not been set.
EVP_CIPHER_get_block_size() and EVP_CIPHER_CTX_get_block_size()
Return the block size of a cipher when passed an EVP_CIPHER or
EVP_CIPHER_CTX structure. The constant EVP_MAX_BLOCK_LENGTH is also
the maximum block length for all ciphers. A value of 0 is returned
if, with EVP_CIPHER_get_block_size(), the cipher e is NULL, or, with
EVP_CIPHER_CTX_get_block_size(), the context ctx is NULL or has not
been properly initialized with a call to EVP_CipherInit.
EVP_CIPHER_get_type() and EVP_CIPHER_CTX_get_type()
Return the type of the passed cipher or context. This "type" is the
actual NID of the cipher OBJECT IDENTIFIER and as such it ignores the
cipher parameters (40 bit RC2 and 128 bit RC2 have the same NID). If
the cipher does not have an object identifier or does not have ASN1
support this function will return NID_undef.
EVP_CIPHER_is_a()
Returns 1 if cipher is an implementation of an algorithm that's
identifiable with name, otherwise 0. If cipher is a legacy cipher
(it's the return value from the likes of EVP_aes128() rather than the
result of an EVP_CIPHER_fetch()), only cipher names registered with
the default library context (see OSSL_LIB_CTX(3)) will be considered.
EVP_CIPHER_get0_name() and EVP_CIPHER_CTX_get0_name()
Return the name of the passed cipher or context. For fetched ciphers
with multiple names, only one of them is returned. See also
EVP_CIPHER_names_do_all(). cipher MUST NOT be NULL.
EVP_CIPHER_names_do_all()
Traverses all names for the cipher, and calls fn with each name and
data. This is only useful with fetched EVP_CIPHERs.
EVP_CIPHER_get0_description()
Returns a description of the cipher, meant for display and human
consumption. The description is at the discretion of the cipher
implementation.
EVP_CIPHER_get0_provider()
Returns an OSSL_PROVIDER pointer to the provider that implements the
given EVP_CIPHER.
EVP_CIPHER_CTX_get0_cipher()
Returns the EVP_CIPHER structure when passed an EVP_CIPHER_CTX
structure. EVP_CIPHER_CTX_get1_cipher() is the same except the
ownership is passed to the caller. Both functions return NULL on
error.
EVP_CIPHER_get_mode() and EVP_CIPHER_CTX_get_mode()
Return the block cipher mode: EVP_CIPH_ECB_MODE, EVP_CIPH_CBC_MODE,
EVP_CIPH_CFB_MODE, EVP_CIPH_OFB_MODE, EVP_CIPH_CTR_MODE,
EVP_CIPH_GCM_MODE, EVP_CIPH_CCM_MODE, EVP_CIPH_XTS_MODE,
EVP_CIPH_WRAP_MODE, EVP_CIPH_OCB_MODE or EVP_CIPH_SIV_MODE. If the
cipher is a stream cipher then EVP_CIPH_STREAM_CIPHER is returned.
EVP_CIPHER_get_flags()
Returns any flags associated with the cipher. See "FLAGS" for a list
of currently defined flags.
EVP_CIPHER_CTX_get_num() and EVP_CIPHER_CTX_set_num()
Gets or sets the cipher specific "num" parameter for the associated
ctx. Built-in ciphers typically use this to track how much of the
current underlying block has been "used" already.
EVP_CIPHER_CTX_is_encrypting()
Reports whether the ctx is being used for encryption or decryption.
EVP_CIPHER_CTX_flags()
A deprecated macro calling
"EVP_CIPHER_get_flags(EVP_CIPHER_CTX_get0_cipher(ctx))". Do not use.
EVP_CIPHER_param_to_asn1()
Sets the AlgorithmIdentifier "parameter" based on the passed cipher.
This will typically include any parameters and an IV. The cipher IV
(if any) must be set when this call is made. This call should be made
before the cipher is actually "used" (before any EVP_EncryptUpdate(),
EVP_DecryptUpdate() calls for example). This function may fail if
the cipher does not have any ASN1 support, or if an uninitialized
cipher is passed to it.
EVP_CIPHER_asn1_to_param()
Sets the cipher parameters based on an ASN1 AlgorithmIdentifier
"parameter". The precise effect depends on the cipher. In the case
of RC2, for example, it will set the IV and effective key length.
This function should be called after the base cipher type is set but
before the key is set. For example EVP_CipherInit() will be called
with the IV and key set to NULL, EVP_CIPHER_asn1_to_param() will be
called and finally EVP_CipherInit() again with all parameters except
the key set to NULL. It is possible for this function to fail if the
cipher does not have any ASN1 support or the parameters cannot be set
(for example the RC2 effective key length is not supported.
EVP_CIPHER_CTX_rand_key()
Generates a random key of the appropriate length based on the cipher
context. The EVP_CIPHER can provide its own random key generation
routine to support keys of a specific form. key must point to a
buffer at least as big as the value returned by
EVP_CIPHER_CTX_get_key_length().
EVP_CIPHER_do_all_provided()
Traverses all ciphers implemented by all activated providers in the
given library context libctx, and for each of the implementations,
calls the given function fn with the implementation method and the
given arg as argument.
PARAMETERS
See OSSL_PARAM(3) for information about passing parameters.
Gettable EVP_CIPHER parameters
When EVP_CIPHER_fetch() is called it internally calls
EVP_CIPHER_get_params() and caches the results.
EVP_CIPHER_get_params() can be used with the following OSSL_PARAM(3)
keys:
"mode" (OSSL_CIPHER_PARAM_MODE) <unsigned integer>
Gets the mode for the associated cipher algorithm cipher. See
"EVP_CIPHER_get_mode() and EVP_CIPHER_CTX_get_mode()" for a list of
valid modes. Use EVP_CIPHER_get_mode() to retrieve the cached value.
"keylen" (OSSL_CIPHER_PARAM_KEYLEN) <unsigned integer>
Gets the key length for the associated cipher algorithm cipher. Use
EVP_CIPHER_get_key_length() to retrieve the cached value.
"ivlen" (OSSL_CIPHER_PARAM_IVLEN) <unsigned integer>
Gets the IV length for the associated cipher algorithm cipher. Use
EVP_CIPHER_get_iv_length() to retrieve the cached value.
"blocksize" (OSSL_CIPHER_PARAM_BLOCK_SIZE) <unsigned integer>
Gets the block size for the associated cipher algorithm cipher. The
block size should be 1 for stream ciphers. Note that the block size
for a cipher may be different to the block size for the underlying
encryption/decryption primitive. For example AES in CTR mode has a
block size of 1 (because it operates like a stream cipher), even
though AES has a block size of 16. Use EVP_CIPHER_get_block_size()
to retrieve the cached value.
"aead" (OSSL_CIPHER_PARAM_AEAD) <integer>
Gets 1 if this is an AEAD cipher algorithm, otherwise it gets 0. Use
(EVP_CIPHER_get_flags(cipher) & EVP_CIPH_FLAG_AEAD_CIPHER) to
retrieve the cached value.
"custom-iv" (OSSL_CIPHER_PARAM_CUSTOM_IV) <integer>
Gets 1 if the cipher algorithm cipher has a custom IV, otherwise it
gets 0. Storing and initializing the IV is left entirely to the
implementation, if a custom IV is used. Use
(EVP_CIPHER_get_flags(cipher) & EVP_CIPH_CUSTOM_IV) to retrieve the
cached value.
"cts" (OSSL_CIPHER_PARAM_CTS) <integer>
Gets 1 if the cipher algorithm cipher uses ciphertext stealing,
otherwise it gets 0. This is currently used to indicate that the
cipher is a one shot that only allows a single call to
EVP_CipherUpdate(). Use (EVP_CIPHER_get_flags(cipher) &
EVP_CIPH_FLAG_CTS) to retrieve the cached value.
"tls-multi" (OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK) <integer>
Gets 1 if the cipher algorithm cipher supports interleaving of crypto
blocks, otherwise it gets 0. The interleaving is an optimization only
applicable to certain TLS ciphers. Use (EVP_CIPHER_get_flags(cipher)
& EVP_CIPH_FLAG_TLS1_1_MULTIBLOCK) to retrieve the cached value.
"has-randkey" (OSSL_CIPHER_PARAM_HAS_RANDKEY) <integer>
Gets 1 if the cipher algorithm cipher supports the gettable
EVP_CIPHER_CTX parameter OSSL_CIPHER_PARAM_RANDOM_KEY. Only DES and
3DES set this to 1, all other OpenSSL ciphers return 0.
"decrypt-only" (OSSL_CIPHER_PARAM_DECRYPT_ONLY) <integer
Gets 1 if the cipher algorithm cipher implementation supports only
the decryption operation such as the 3DES ciphers in the fips
provider. Otherwise gets 0 or the parameter might not be present at
all.
Gettable and Settable EVP_CIPHER_CTX parameters
The following OSSL_PARAM(3) keys can be used with both
EVP_CIPHER_CTX_get_params() and EVP_CIPHER_CTX_set_params().
"padding" (OSSL_CIPHER_PARAM_PADDING) <unsigned integer>
Gets or sets the padding mode for the cipher context ctx. Padding is
enabled if the value is 1, and disabled if the value is 0. See also
EVP_CIPHER_CTX_set_padding().
"num" (OSSL_CIPHER_PARAM_NUM) <unsigned integer>
Gets or sets the cipher specific "num" parameter for the cipher
context ctx. Built-in ciphers typically use this to track how much
of the current underlying block has been "used" already. See also
EVP_CIPHER_CTX_get_num() and EVP_CIPHER_CTX_set_num().
"keylen" (OSSL_CIPHER_PARAM_KEYLEN) <unsigned integer>
Gets or sets the key length for the cipher context ctx. The length
of the "keylen" parameter should not exceed that of a size_t. See
also EVP_CIPHER_CTX_get_key_length() and
EVP_CIPHER_CTX_set_key_length().
"tag" (OSSL_CIPHER_PARAM_AEAD_TAG) <octet string>
Gets or sets the AEAD tag for the associated cipher context ctx. See
"AEAD INTERFACE" in EVP_EncryptInit(3).
"pipeline-tag" (OSSL_CIPHER_PARAM_PIPELINE_AEAD_TAG) <octet ptr>
Gets or sets the AEAD tag when using cipher pipelining. The pointer
must point to an array of buffers, where the aead tag will be read
from or written to. The array size must be equal to numpipes used in
EVP_CipherPipelineEncryptInit() or EVP_CipherPipelineDecryptInit().
"keybits" (OSSL_CIPHER_PARAM_RC2_KEYBITS) <unsigned integer>
Gets or sets the effective keybits used for a RC2 cipher. The length
of the "keybits" parameter should not exceed that of a size_t.
"rounds" (OSSL_CIPHER_PARAM_ROUNDS) <unsigned integer>
Gets or sets the number of rounds to be used for a cipher. This is
used by the RC5 cipher.
"algorithm-id" (OSSL_CIPHER_PARAM_ALGORITHM_ID) <octet string>
Used to get the DER encoded AlgorithmIdentifier from the cipher
implementation. Functions like EVP_PKEY_CTX_get_algor(3) use this
parameter.
"algorithm-id-params" (OSSL_CIPHER_PARAM_ALGORITHM_ID_PARAMS) <octet
string>
Used to pass the DER encoded AlgorithmIdentifier parameter to or from
the cipher implementation. Functions like
EVP_CIPHER_CTX_set_algor_params(3) and
EVP_CIPHER_CTX_get_algor_params(3) use this parameter.
"alg_id_params" (OSSL_CIPHER_PARAM_ALGORITHM_ID_PARAMS_OLD) <octet
string>
An deprecated alias for "algorithm-id-params", only used by
EVP_CIPHER_param_to_asn1(3) and EVP_CIPHER_asn1_to_param(3).
"cts_mode" (OSSL_CIPHER_PARAM_CTS_MODE) <UTF8 string>
Gets or sets the cipher text stealing mode. For all modes the output
size is the same as the input size. The input length must be greater
than or equal to the block size. (The block size for AES and CAMELLIA
is 16 bytes).
Valid values for the mode are:
"CS1"
The NIST variant of cipher text stealing. For input lengths that
are multiples of the block size it is equivalent to using a "AES-
XXX-CBC" or "CAMELLIA-XXX-CBC" cipher otherwise the second last
cipher text block is a partial block.
"CS2"
For input lengths that are multiples of the block size it is
equivalent to using a "AES-XXX-CBC" or "CAMELLIA-XXX-CBC" cipher,
otherwise it is the same as "CS3" mode.
"CS3"
The Kerberos5 variant of cipher text stealing which always swaps
the last cipher text block with the previous block (which may be
a partial or full block depending on the input length). If the
input length is exactly one full block then this is equivalent to
using a "AES-XXX-CBC" or "CAMELLIA-XXX-CBC" cipher.
The default is "CS1". This is only supported for "AES-128-CBC-CTS",
"AES-192-CBC-CTS", "AES-256-CBC-CTS", "CAMELLIA-128-CBC-CTS",
"CAMELLIA-192-CBC-CTS" and "CAMELLIA-256-CBC-CTS".
"tls1multi_interleave" (OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_INTERLEAVE)
<unsigned integer>
Sets or gets the number of records being sent in one go for a tls1
multiblock cipher operation (either 4 or 8 records).
Gettable EVP_CIPHER_CTX parameters
The following OSSL_PARAM(3) keys can be used with
EVP_CIPHER_CTX_get_params():
"ivlen" (OSSL_CIPHER_PARAM_IVLEN and <OSSL_CIPHER_PARAM_AEAD_IVLEN)
<unsigned integer>
Gets the IV length for the cipher context ctx. The length of the
"ivlen" parameter should not exceed that of a size_t. See also
EVP_CIPHER_CTX_get_iv_length().
"iv" (OSSL_CIPHER_PARAM_IV) <octet string OR octet ptr>
Gets the IV used to initialize the associated cipher context ctx.
See also EVP_CIPHER_CTX_get_original_iv().
"updated-iv" (OSSL_CIPHER_PARAM_UPDATED_IV) <octet string OR octet ptr>
Gets the updated pseudo-IV state for the associated cipher context,
e.g., the previous ciphertext block for CBC mode or the iteratively
encrypted IV value for OFB mode. Note that octet pointer access is
deprecated and is provided only for backwards compatibility with
historical libcrypto APIs. See also EVP_CIPHER_CTX_get_updated_iv().
"randkey" (OSSL_CIPHER_PARAM_RANDOM_KEY) <octet string>
Gets an implementation specific randomly generated key for the
associated cipher context ctx. This is currently only supported by
DES and 3DES (which set the key to odd parity).
"taglen" (OSSL_CIPHER_PARAM_AEAD_TAGLEN) <unsigned integer>
Gets the tag length to be used for an AEAD cipher for the associated
cipher context ctx. It gets a default value if it has not been set.
The length of the "taglen" parameter should not exceed that of a
size_t. See also EVP_CIPHER_CTX_get_tag_length().
"tlsaadpad" (OSSL_CIPHER_PARAM_AEAD_TLS1_AAD_PAD) <unsigned integer>
Gets the length of the tag that will be added to a TLS record for the
AEAD tag for the associated cipher context ctx. The length of the
"tlsaadpad" parameter should not exceed that of a size_t.
"tlsivgen" (OSSL_CIPHER_PARAM_AEAD_TLS1_GET_IV_GEN) <octet string>
Gets the invocation field generated for encryption. Can only be
called after "tlsivfixed" is set. This is only used for GCM mode.
"tls1multi_enclen" (OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_ENC_LEN) <unsigned
integer>
Get the total length of the record returned from the "tls1multi_enc"
operation.
"tls1multi_maxbufsz" (OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_MAX_BUFSIZE)
<unsigned integer>
Gets the maximum record length for a TLS1 multiblock cipher
operation. The length of the "tls1multi_maxbufsz" parameter should
not exceed that of a size_t.
"tls1multi_aadpacklen" (OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_AAD_PACKLEN)
<unsigned integer>
Gets the result of running the "tls1multi_aad" operation.
"tls-mac" (OSSL_CIPHER_PARAM_TLS_MAC) <octet ptr>
Used to pass the TLS MAC data.
"fips-indicator" (OSSL_CIPHER_PARAM_FIPS_APPROVED_INDICATOR) <integer>
This option is used by the OpenSSL FIPS provider.
A getter that returns 1 if the operation is FIPS approved, or 0
otherwise. This may be used after calling a cipher final operation
such as EVP_EncryptFinal_ex(). It may return 0 if the "encrypt-check"
option is set to 0. For GCM encryption it also returns 0 if the IV
was supplied externally instead of being generated by the FIPS
provider. The separate "iv-generated" parameter reports the IV
source directly, but callers can use "fips-indicator" to determine
the overall approval status. For GCM encryption and decryption, tag
lengths other than 4, 8, or 12 through 16 bytes also cause this
indicator to return 0.
"iv-generated" (OSSL_CIPHER_PARAM_AEAD_IV_GENERATED) <unsigned integer>
An indicator that returns 1 if an IV was generated internally during
encryption, or 0 otherwise. This may be used by GCM ciphers after
calling a cipher final operation such as EVP_EncryptFinal_ex(). GCM
should generate an IV internally if the IV is not specified during a
cipher initialisation call such as EVP_CipherInit_ex(). See FIPS
140-3 IG C.H for information related to IV requirements.
Settable EVP_CIPHER_CTX parameters
The following OSSL_PARAM(3) keys can be used with
EVP_CIPHER_CTX_set_params():
"mackey" (OSSL_CIPHER_PARAM_AEAD_MAC_KEY) <octet string>
Sets the MAC key used by composite AEAD ciphers such as
AES-CBC-HMAC-SHA256.
"speed" (OSSL_CIPHER_PARAM_SPEED) <unsigned integer>
Sets the speed option for the associated cipher context. This is only
supported by AES SIV ciphers which disallow multiple operations by
default. Setting "speed" to 1 allows another encrypt or decrypt
operation to be performed. This is used for performance testing.
"use-bits" (OSSL_CIPHER_PARAM_USE_BITS) <unsigned integer>
Determines if the input length inl passed to EVP_EncryptUpdate(),
EVP_DecryptUpdate() and EVP_CipherUpdate() is the number of bits or
number of bytes. Setting "use-bits" to 1 uses bits. The default is
in bytes. This is only used for CFB1 ciphers.
This can be set using EVP_CIPHER_CTX_set_flags(ctx,
EVP_CIPH_FLAG_LENGTH_BITS).
"tls-version" (OSSL_CIPHER_PARAM_TLS_VERSION) <integer>
Sets the TLS version.
"tls-mac-size" (OSSL_CIPHER_PARAM_TLS_MAC_SIZE) <unsigned integer>
Set the TLS MAC size.
"tlsaad" (OSSL_CIPHER_PARAM_AEAD_TLS1_AAD) <octet string>
Sets TLSv1.2 AAD information for the associated cipher context ctx.
TLSv1.2 AAD information is always 13 bytes in length and is as
defined for the "additional_data" field described in section 6.2.3.3
of RFC5246.
"tlsivfixed" (OSSL_CIPHER_PARAM_AEAD_TLS1_IV_FIXED) <octet string>
Sets the fixed portion of an IV for an AEAD cipher used in a TLS
record encryption/ decryption for the associated cipher context. TLS
record encryption/decryption always occurs "in place" so that the
input and output buffers are always the same memory location. AEAD
IVs in TLSv1.2 consist of an implicit "fixed" part and an explicit
part that varies with every record. Setting a TLS fixed IV changes a
cipher to encrypt/decrypt TLS records. TLS records are
encrypted/decrypted using a single OSSL_FUNC_cipher_cipher call per
record. For a record decryption the first bytes of the input buffer
will be the explicit part of the IV and the final bytes of the input
buffer will be the AEAD tag. The length of the explicit part of the
IV and the tag length will depend on the cipher in use and will be
defined in the RFC for the relevant ciphersuite. In order to allow
for "in place" decryption the plaintext output should be written to
the same location in the output buffer that the ciphertext payload
was read from, i.e. immediately after the explicit IV.
When encrypting a record the first bytes of the input buffer should
be empty to allow space for the explicit IV, as will the final bytes
where the tag will be written. The length of the input buffer will
include the length of the explicit IV, the payload, and the tag
bytes. The cipher implementation should generate the explicit IV and
write it to the beginning of the output buffer, do "in place"
encryption of the payload and write that to the output buffer, and
finally add the tag onto the end of the output buffer.
Whether encrypting or decrypting the value written to *outl in the
OSSL_FUNC_cipher_cipher call should be the length of the payload
excluding the explicit IV length and the tag length.
"tlsivinv" (OSSL_CIPHER_PARAM_AEAD_TLS1_SET_IV_INV) <octet string>
Sets the invocation field used for decryption. Can only be called
after "tlsivfixed" is set. This is only used for GCM mode.
"tls1multi_enc" (OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_ENC) <octet string>
Triggers a multiblock TLS1 encrypt operation for a TLS1 aware cipher
that supports sending 4 or 8 records in one go. The cipher performs
both the MAC and encrypt stages and constructs the record headers
itself. "tls1multi_enc" supplies the output buffer for the encrypt
operation, "tls1multi_encin" & "tls1multi_interleave" must also be
set in order to supply values to the encrypt operation.
"tls1multi_encin" (OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_ENC_IN) <octet
string>
Supplies the data to encrypt for a TLS1 multiblock cipher operation.
"tls1multi_maxsndfrag"
(OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_MAX_SEND_FRAGMENT) <unsigned integer>
Sets the maximum send fragment size for a TLS1 multiblock cipher
operation. It must be set before using "tls1multi_maxbufsz". The
length of the "tls1multi_maxsndfrag" parameter should not exceed that
of a size_t.
"tls1multi_aad" (OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_AAD) <octet string>
Sets the authenticated additional data used by a TLS1 multiblock
cipher operation. The supplied data consists of 13 bytes of record
data containing: Bytes 0-7: The sequence number of the first record
Byte 8: The record type Byte 9-10: The protocol version Byte 11-12:
Input length (Always 0)
"tls1multi_interleave" must also be set for this operation.
"xts_standard" (OSSL_CIPHER_PARAM_XTS_STANDARD) <UTF8 string>
Sets the XTS standard to use with SM4-XTS algorithm. XTS mode has two
implementations, one is standardized in IEEE Std. 1619-2007 and has
been widely used (e.g., XTS AES), the other is proposed recently
(GB/T 17964-2021 implemented in May 2022) and is currently only used
in SM4.
The main difference between them is the multiplication by the
primitive element X to calculate the tweak values. The IEEE Std
1619-2007 noted that the multiplication "is a left shift of each byte
by one bit with carry propagating from one byte to the next one",
which means that in each byte, the leftmost bit is the most
significant bit. But in GB/T 17964-2021, the rightmost bit is the
most significant bit, thus the multiplication becomes a right shift
of each byte by one bit with carry propagating from one byte to the
next one.
Valid values for the mode are:
"GB"
The GB/T 17964-2021 variant of SM4-XTS algorithm.
"IEEE"
The IEEE Std. 1619-2007 variant of SM4-XTS algorithm.
The default value is "GB".
"encrypt-check" (OSSL_CIPHER_PARAM_FIPS_ENCRYPT_CHECK) <integer>
This option is used by the OpenSSL FIPS provider.
If required this parameter should be set early via an cipher encrypt
init function such as EVP_EncryptInit_ex2(). The default value of 1
causes an error when an encryption operation is triggered. Setting
this to 0 will ignore the error and set the approved "fips-indicator"
to 0. This option breaks FIPS compliance if it causes the approved
"fips-indicator" to return 0.
CONTROLS
The Mappings from EVP_CIPHER_CTX_ctrl() identifiers to PARAMETERS are
listed in the following section. See the "PARAMETERS" section for more
details.
EVP_CIPHER_CTX_ctrl() can be used to send the following standard
controls:
EVP_CTRL_AEAD_SET_IVLEN and EVP_CTRL_GET_IVLEN
When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params() and
EVP_CIPHER_CTX_get_params() get called with an OSSL_PARAM(3) item
with the key "ivlen" (OSSL_CIPHER_PARAM_IVLEN).
EVP_CTRL_AEAD_SET_IV_FIXED
When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params() gets
called with an OSSL_PARAM(3) item with the key "tlsivfixed"
(OSSL_CIPHER_PARAM_AEAD_TLS1_IV_FIXED).
EVP_CTRL_AEAD_SET_MAC_KEY
When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params() gets
called with an OSSL_PARAM(3) item with the key "mackey"
(OSSL_CIPHER_PARAM_AEAD_MAC_KEY).
EVP_CTRL_AEAD_SET_TAG and EVP_CTRL_AEAD_GET_TAG
When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params() and
EVP_CIPHER_CTX_get_params() get called with an OSSL_PARAM(3) item
with the key "tag" (OSSL_CIPHER_PARAM_AEAD_TAG).
EVP_CTRL_CCM_SET_L
When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params() gets
called with an OSSL_PARAM(3) item with the key "ivlen"
(OSSL_CIPHER_PARAM_IVLEN) with a value of (15 - L)
EVP_CTRL_COPY
There is no OSSL_PARAM mapping for this. Use EVP_CIPHER_CTX_copy()
instead.
EVP_CTRL_GCM_SET_IV_INV
When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params() gets
called with an OSSL_PARAM(3) item with the key "tlsivinv"
(OSSL_CIPHER_PARAM_AEAD_TLS1_SET_IV_INV).
EVP_CTRL_RAND_KEY
When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params() gets
called with an OSSL_PARAM(3) item with the key "randkey"
(OSSL_CIPHER_PARAM_RANDOM_KEY).
EVP_CTRL_SET_KEY_LENGTH
When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params() gets
called with an OSSL_PARAM(3) item with the key "keylen"
(OSSL_CIPHER_PARAM_KEYLEN).
EVP_CTRL_SET_RC2_KEY_BITS and EVP_CTRL_GET_RC2_KEY_BITS
When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params() and
EVP_CIPHER_CTX_get_params() get called with an OSSL_PARAM(3) item
with the key "keybits" (OSSL_CIPHER_PARAM_RC2_KEYBITS).
EVP_CTRL_SET_RC5_ROUNDS and EVP_CTRL_GET_RC5_ROUNDS
When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params() and
EVP_CIPHER_CTX_get_params() get called with an OSSL_PARAM(3) item
with the key "rounds" (OSSL_CIPHER_PARAM_ROUNDS).
EVP_CTRL_SET_SPEED
When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params() gets
called with an OSSL_PARAM(3) item with the key "speed"
(OSSL_CIPHER_PARAM_SPEED).
EVP_CTRL_GCM_IV_GEN
When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_get_params() gets
called with an OSSL_PARAM(3) item with the key "tlsivgen"
(OSSL_CIPHER_PARAM_AEAD_TLS1_GET_IV_GEN).
EVP_CTRL_AEAD_TLS1_AAD
When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params() get
called with an OSSL_PARAM(3) item with the key "tlsaad"
(OSSL_CIPHER_PARAM_AEAD_TLS1_AAD) followed by
EVP_CIPHER_CTX_get_params() with a key of "tlsaadpad"
(OSSL_CIPHER_PARAM_AEAD_TLS1_AAD_PAD).
EVP_CTRL_TLS1_1_MULTIBLOCK_MAX_BUFSIZE
When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params() gets
called with an OSSL_PARAM(3) item with the key
OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_MAX_SEND_FRAGMENT followed by
EVP_CIPHER_CTX_get_params() with a key of "tls1multi_maxbufsz"
(OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_MAX_BUFSIZE).
EVP_CTRL_TLS1_1_MULTIBLOCK_AAD
When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params() gets
called with OSSL_PARAM(3) items with the keys "tls1multi_aad"
(OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_AAD) and "tls1multi_interleave"
(OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_INTERLEAVE) followed by
EVP_CIPHER_CTX_get_params() with keys of "tls1multi_aadpacklen"
(OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_AAD_PACKLEN) and
"tls1multi_interleave"
(OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_INTERLEAVE).
EVP_CTRL_TLS1_1_MULTIBLOCK_ENCRYPT
When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params() gets
called with OSSL_PARAM(3) items with the keys "tls1multi_enc"
(OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_ENC), "tls1multi_encin"
(OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_ENC_IN) and "tls1multi_interleave"
(OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_INTERLEAVE), followed by
EVP_CIPHER_CTX_get_params() with a key of "tls1multi_enclen"
(OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_ENC_LEN).
FLAGS
EVP_CIPHER_CTX_set_flags(), EVP_CIPHER_CTX_clear_flags() and
EVP_CIPHER_CTX_test_flags(). can be used to manipulate and test these
EVP_CIPHER_CTX flags:
EVP_CIPH_NO_PADDING
Used by EVP_CIPHER_CTX_set_padding().
See also "Gettable and Settable EVP_CIPHER_CTX parameters" "padding"
EVP_CIPH_FLAG_LENGTH_BITS
See "Settable EVP_CIPHER_CTX parameters" "use-bits".
EVP_CIPHER_CTX_FLAG_WRAP_ALLOW
Used for Legacy purposes only. This flag needed to be set to indicate
the cipher handled wrapping.
EVP_CIPHER_flags() uses the following flags that have mappings to
"Gettable EVP_CIPHER parameters":
EVP_CIPH_FLAG_AEAD_CIPHER
See "Gettable EVP_CIPHER parameters" "aead".
EVP_CIPH_CUSTOM_IV
See "Gettable EVP_CIPHER parameters" "custom-iv".
EVP_CIPH_FLAG_CTS
See "Gettable EVP_CIPHER parameters" "cts".
EVP_CIPH_FLAG_TLS1_1_MULTIBLOCK;
See "Gettable EVP_CIPHER parameters" "tls-multi".
EVP_CIPH_RAND_KEY
See "Gettable EVP_CIPHER parameters" "has-randkey".
EVP_CIPHER_flags() uses the following flags for legacy purposes only:
EVP_CIPH_VARIABLE_LENGTH
EVP_CIPH_FLAG_CUSTOM_CIPHER
EVP_CIPH_ALWAYS_CALL_INIT
EVP_CIPH_CTRL_INIT
EVP_CIPH_CUSTOM_KEY_LENGTH
EVP_CIPH_CUSTOM_COPY
EVP_CIPH_FLAG_DEFAULT_ASN1
See EVP_CIPHER_meth_set_flags(3) for further information related to
the above flags.
RETURN VALUES
EVP_CIPHER_fetch() returns a pointer to a EVP_CIPHER for success and NULL
for failure.
EVP_CIPHER_up_ref() returns 1 for success or 0 otherwise.
EVP_CIPHER_CTX_new() returns a pointer to a newly created EVP_CIPHER_CTX
for success and NULL for failure.
EVP_CIPHER_CTX_dup() returns a new EVP_CIPHER_CTX if successful or NULL
on failure.
EVP_CIPHER_CTX_copy() returns 1 if successful or 0 for failure.
EVP_EncryptInit_ex2(), EVP_EncryptUpdate() and EVP_EncryptFinal_ex()
return 1 for success and 0 for failure.
EVP_DecryptInit_ex2() and EVP_DecryptUpdate() return 1 for success and 0
for failure. EVP_DecryptFinal_ex() returns 0 if the decrypt failed or 1
for success.
EVP_CipherInit_ex2(), EVP_CipherInit_SKEY() and EVP_CipherUpdate() return
1 for success and 0 for failure. EVP_CipherFinal_ex() returns 0 for an
encryption/decryption failure or 1 for success.
EVP_Cipher() returns 1 on success and <= 0 on failure, if the flag
EVP_CIPH_FLAG_CUSTOM_CIPHER is not set for the cipher, or if the cipher
has not been initialized via a call to EVP_CipherInit_ex2. EVP_Cipher()
returns the number of bytes written to out for encryption/decryption, or
the number of bytes authenticated in a call specifying AAD for an AEAD
cipher, if the flag EVP_CIPH_FLAG_CUSTOM_CIPHER is set for the cipher.
EVP_CIPHER_can_pipeline() returns 1 if the cipher can be used in a
pipeline, 0 otherwise.
EVP_CipherPipelineEncryptInit() and EVP_CipherPipelineDecryptInit()
return 1 for success and 0 for failure.
EVP_CipherPipelineUpdate() and EVP_CipherPipelineFinal() return 1 for
success and 0 for failure.
EVP_CIPHER_CTX_reset() returns 1 for success and 0 for failure.
EVP_get_cipherbyname(), EVP_get_cipherbynid() and EVP_get_cipherbyobj()
return an EVP_CIPHER structure or NULL on error.
EVP_CIPHER_get_nid() and EVP_CIPHER_CTX_get_nid() return a NID.
EVP_CIPHER_get_block_size() and EVP_CIPHER_CTX_get_block_size() return
the block size, or 0 on error.
EVP_CIPHER_get_key_length() and EVP_CIPHER_CTX_get_key_length() return
the key length.
EVP_CIPHER_CTX_set_padding() always returns 1.
EVP_CIPHER_get_iv_length() and EVP_CIPHER_CTX_get_iv_length() return the
IV length, zero if the cipher does not use an IV and a negative value on
error.
EVP_CIPHER_CTX_get_tag_length() return the tag length or zero if the
cipher does not use a tag.
EVP_CIPHER_get_type() and EVP_CIPHER_CTX_get_type() return the NID of the
cipher's OBJECT IDENTIFIER or NID_undef if it has no defined OBJECT
IDENTIFIER.
EVP_CIPHER_CTX_cipher() returns an EVP_CIPHER structure.
EVP_CIPHER_CTX_get_num() returns a nonnegative num value or
EVP_CTRL_RET_UNSUPPORTED if the implementation does not support the call
or on any other error.
EVP_CIPHER_CTX_set_num() returns 1 on success and 0 if the implementation
does not support the call or on any other error.
EVP_CIPHER_CTX_is_encrypting() returns 1 if the ctx is set up for
encryption 0 otherwise.
EVP_CIPHER_param_to_asn1() and EVP_CIPHER_asn1_to_param() return greater
than zero for success and zero or a negative number on failure.
EVP_CIPHER_CTX_rand_key() returns 1 for success and zero or a negative
number for failure.
EVP_CIPHER_names_do_all() returns 1 if the callback was called for all
names. A return value of 0 means that the callback was not called for
any names.
EVP_CIPHER_get_params(), EVP_CIPHER_CTX_get_params() and
EVP_CIPHER_CTX_set_params() return 1 for success and 0 for failure.
CIPHER LISTING
All algorithms have a fixed key length unless otherwise stated.
Refer to "SEE ALSO" for the full list of ciphers available through the
EVP interface.
EVP_enc_null()
Null cipher: does nothing.
AEAD INTERFACE
The EVP interface for Authenticated Encryption with Associated Data
(AEAD) modes are subtly altered and several additional ctrl operations
are supported depending on the mode specified.
To specify additional authenticated data (AAD), a call to
EVP_CipherUpdate(), EVP_EncryptUpdate() or EVP_DecryptUpdate() should be
made with the output parameter out set to NULL. In this case, on success,
the parameter outl is set to the number of AAD bytes processed in that
call (that is, the value of inl), and does not include any plaintext or
ciphertext bytes processed by other calls.
If no AAD is used, this call can be omitted. See the mode-specific notes
below for any exceptions.
When decrypting, the return value of EVP_DecryptFinal() or
EVP_CipherFinal() indicates whether the operation was successful. If it
does not indicate success, the authentication operation has failed and
any output data MUST NOT be used as it is corrupted.
Please note that the number of authenticated bytes returned by
EVP_CipherUpdate() depends on the cipher used. Stream ciphers, such as
ChaCha20 or ciphers in GCM mode, can handle 1 byte at a time, resulting
in an effective "block" size of 1. Conversely, ciphers in OCB mode must
process data one block at a time, and the block size is returned.
Regardless of the returned size, it is safe to pass unpadded data to an
EVP_CipherUpdate() call in a single operation.
GCM and OCB Modes
The following ctrls are supported in GCM and OCB modes.
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_IVLEN, ivlen, NULL)
Sets the IV length. This call can only be made before specifying an
IV. If not called a default IV length is used.
For GCM AES and OCB AES the default is 12 (i.e. 96 bits). For OCB
mode the maximum is 15.
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_GET_TAG, taglen, tag)
Writes "taglen" bytes of the tag value to the buffer indicated by
"tag". This call can only be made when encrypting data and after all
data has been processed (e.g. after an EVP_EncryptFinal() call).
For OCB, "taglen" must either be 16 or the value previously set via
EVP_CTRL_AEAD_SET_TAG.
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag)
When decrypting, this call sets the expected tag to "taglen" bytes
from "tag". "taglen" must be between 1 and 16 inclusive. The tag
must be set prior to any call to EVP_DecryptFinal() or
EVP_DecryptFinal_ex().
For GCM, this call is only valid when decrypting data.
For OCB, this call is valid when decrypting data to set the expected
tag, and when encrypting to set the desired tag length.
In OCB mode, calling this with "tag" set to "NULL" sets the tag
length. The tag length can only be set before specifying an IV. If
this is not called prior to setting the IV, then a default tag length
is used.
For OCB AES, the default tag length is 16 (i.e. 128 bits). It is
also the maximum tag length for OCB.
CCM Mode
The EVP interface for CCM mode is similar to that of the GCM mode but
with a few additional requirements and different ctrl values.
For CCM mode, the total plaintext or ciphertext length MUST be passed to
EVP_CipherUpdate(), EVP_EncryptUpdate() or EVP_DecryptUpdate() with the
output and input parameters (in and out) set to NULL and the length
passed in the inl parameter.
The following ctrls are supported in CCM mode.
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag)
This call is made to set the expected CCM tag value when decrypting
or the length of the tag (with the "tag" parameter set to NULL) when
encrypting. The tag length is often referred to as M. If not set a
default value is used (12 for AES). When decrypting, the tag needs to
be set before passing in data to be decrypted, but as in GCM and OCB
mode, it can be set after passing additional authenticated data (see
"AEAD INTERFACE").
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_CCM_SET_L, ivlen, NULL)
Sets the CCM L value. If not set a default is used (8 for AES).
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_IVLEN, ivlen, NULL)
Sets the CCM nonce (IV) length. This call can only be made before
specifying a nonce value. The nonce length is given by 15 - L so it
is 7 by default for AES.
SIV Mode
Both the AES-SIV and AES-GCM-SIV ciphers fall under this mode.
For SIV mode ciphers the behaviour of the EVP interface is subtly altered
and several additional ctrl operations are supported.
To specify any additional authenticated data (AAD) and/or a Nonce, a call
to EVP_CipherUpdate(), EVP_EncryptUpdate() or EVP_DecryptUpdate() should
be made with the output parameter out set to NULL.
RFC5297 states that the Nonce is the last piece of AAD before the actual
encrypt/decrypt takes place. The API does not differentiate the Nonce
from other AAD.
When decrypting the return value of EVP_DecryptFinal() or
EVP_CipherFinal() indicates if the operation was successful. If it does
not indicate success the authentication operation has failed and any
output data MUST NOT be used as it is corrupted.
The API does not store the SIV (Synthetic Initialization Vector) in the
cipher text. Instead, it is stored as the tag within the EVP_CIPHER_CTX.
The SIV must be retrieved from the context after encryption, and set into
the context before decryption.
This differs from RFC5297 in that the cipher output from encryption, and
the cipher input to decryption, does not contain the SIV. This also means
that the plain text and cipher text lengths are identical.
The following ctrls are supported in SIV mode, and are used to get and
set the Synthetic Initialization Vector:
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_GET_TAG, taglen, tag);
Writes taglen bytes of the tag value (the Synthetic Initialization
Vector) to the buffer indicated by tag. This call can only be made
when encrypting data and after all data has been processed (e.g.
after an EVP_EncryptFinal() call). For SIV mode the taglen must be
16.
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag);
Sets the expected tag (the Synthetic Initialization Vector) to taglen
bytes from tag. This call is only legal when decrypting data and must
be made before any data is processed (e.g. before any
EVP_DecryptUpdate() calls). For SIV mode the taglen must be 16.
SIV mode makes two passes over the input data, thus, only one call to
EVP_CipherUpdate(), EVP_EncryptUpdate() or EVP_DecryptUpdate() should be
made with out set to a non-NULL value. A call to EVP_DecryptFinal() or
EVP_CipherFinal() is not required, but will indicate if the update
operation succeeded.
ChaCha20-Poly1305
The following ctrls are supported for the ChaCha20-Poly1305 AEAD
algorithm.
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_IVLEN, ivlen, NULL)
Sets the nonce length. This call is now redundant since the only
valid value is the default length of 12 (i.e. 96 bits). Prior to
OpenSSL 3.0 a nonce of less than 12 bytes could be used to
automatically pad the iv with leading 0 bytes to make it 12 bytes in
length.
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_GET_TAG, taglen, tag)
Writes "taglen" bytes of the tag value to the buffer indicated by
"tag". This call can only be made when encrypting data and after all
data has been processed (e.g. after an EVP_EncryptFinal() call).
"taglen" specified here must be 16 (POLY1305_BLOCK_SIZE, i.e.
128-bits) or less.
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag)
Sets the expected tag to "taglen" bytes from "tag". The tag length
can only be set before specifying an IV. "taglen" must be between 1
and 16 (POLY1305_BLOCK_SIZE) inclusive. This call is only valid when
decrypting data.
NOTES
Where possible the EVP interface to symmetric ciphers should be used in
preference to the low-level interfaces. This is because the code then
becomes transparent to the cipher used and much more flexible.
Additionally, the EVP interface will ensure the use of platform specific
cryptographic acceleration such as AES-NI (the low-level interfaces do
not provide the guarantee).
PKCS padding works by adding n padding bytes of value n to make the total
length of the encrypted data a multiple of the block size. Padding is
always added so if the data is already a multiple of the block size n
will equal the block size. For example if the block size is 8 and 11
bytes are to be encrypted then 5 padding bytes of value 5 will be added.
When decrypting the final block is checked to see if it has the correct
form.
Although the decryption operation can produce an error if padding is
enabled, it is not a strong test that the input data or key is correct. A
random block has better than 1 in 256 chance of being of the correct
format and problems with the input data earlier on will not produce a
final decrypt error.
If padding is disabled then the decryption operation will always succeed
if the total amount of data decrypted is a multiple of the block size.
The functions EVP_EncryptInit(3), EVP_EncryptInit_ex(),
EVP_EncryptFinal(), EVP_DecryptInit(), EVP_DecryptInit_ex(),
EVP_CipherInit(), EVP_CipherInit_ex() and EVP_CipherFinal() are obsolete
but are retained for compatibility with existing code. New code should
use EVP_EncryptInit_ex2(), EVP_EncryptFinal_ex(), EVP_DecryptInit_ex2(),
EVP_DecryptFinal_ex(), EVP_CipherInit_ex2() and EVP_CipherFinal_ex()
because they can reuse an existing context without allocating and freeing
it up on each call.
There are some differences between functions EVP_CipherInit() and
EVP_CipherInit_ex(), significant in some circumstances. EVP_CipherInit()
fills the passed context object with zeros. As a consequence,
EVP_CipherInit() does not allow step-by-step initialization of the ctx
when the key and iv are passed in separate calls. It also means that the
flags set for the CTX are removed, and it is especially important for the
EVP_CIPHER_CTX_FLAG_WRAP_ALLOW flag treated specially in
EVP_CipherInit_ex().
Ignoring failure returns of the EVP_CIPHER_CTX initialization functions
can lead to subsequent undefined behavior when calling the functions that
update or finalize the context. The only valid calls on the
EVP_CIPHER_CTX when initialization fails are calls that attempt another
initialization of the context or release the context.
EVP_get_cipherbynid(), and EVP_get_cipherbyobj() are implemented as
macros.
BUGS
EVP_MAX_KEY_LENGTH and EVP_MAX_IV_LENGTH only refer to the internal
ciphers with default key lengths. If custom ciphers exceed these values
the results are unpredictable. This is because it has become standard
practice to define a generic key as a fixed unsigned char array
containing EVP_MAX_KEY_LENGTH bytes.
The ASN1 code is incomplete (and sometimes inaccurate) it has only been
tested for certain common S/MIME ciphers (RC2, DES, triple DES) in CBC
mode.
EXAMPLES
Encrypt a string using IDEA:
int do_crypt(char *outfile)
{
unsigned char outbuf[1024];
int outlen, tmplen;
/*
* Bogus key and IV: we'd normally set these from
* another source.
*/
unsigned char key[] = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15};
unsigned char iv[] = {1,2,3,4,5,6,7,8};
char intext[] = "Some Crypto Text";
EVP_CIPHER_CTX *ctx;
FILE *out;
ctx = EVP_CIPHER_CTX_new();
if (!EVP_EncryptInit_ex2(ctx, EVP_idea_cbc(), key, iv, NULL)) {
/* Error */
EVP_CIPHER_CTX_free(ctx);
return 0;
}
if (!EVP_EncryptUpdate(ctx, outbuf, &outlen, intext, strlen(intext))) {
/* Error */
EVP_CIPHER_CTX_free(ctx);
return 0;
}
/*
* Buffer passed to EVP_EncryptFinal() must be after data just
* encrypted to avoid overwriting it.
*/
if (!EVP_EncryptFinal_ex(ctx, outbuf + outlen, &tmplen)) {
/* Error */
EVP_CIPHER_CTX_free(ctx);
return 0;
}
outlen += tmplen;
EVP_CIPHER_CTX_free(ctx);
/*
* Need binary mode for fopen because encrypted data is
* binary data. Also cannot use strlen() on it because
* it won't be NUL terminated and may contain embedded
* NULs.
*/
out = fopen(outfile, "wb");
if (out == NULL) {
/* Error */
return 0;
}
fwrite(outbuf, 1, outlen, out);
fclose(out);
return 1;
}
The ciphertext from the above example can be decrypted using the openssl
utility with the command line (shown on two lines for clarity):
openssl idea -d \
-K 000102030405060708090A0B0C0D0E0F -iv 0102030405060708 <filename
General encryption and decryption function example using FILE I/O and
AES128 with a 128-bit key:
int do_crypt(FILE *in, FILE *out, int do_encrypt)
{
/* Allow enough space in output buffer for additional block */
unsigned char inbuf[1024], outbuf[1024 + EVP_MAX_BLOCK_LENGTH];
int inlen, outlen;
EVP_CIPHER_CTX *ctx;
/*
* Bogus key and IV: we'd normally set these from
* another source.
*/
unsigned char key[] = "0123456789abcdeF";
unsigned char iv[] = "1234567887654321";
/* Don't set key or IV right away; we want to check lengths */
ctx = EVP_CIPHER_CTX_new();
if (!EVP_CipherInit_ex2(ctx, EVP_aes_128_cbc(), NULL, NULL,
do_encrypt, NULL)) {
/* Error */
EVP_CIPHER_CTX_free(ctx);
return 0;
}
OPENSSL_assert(EVP_CIPHER_CTX_get_key_length(ctx) == 16);
OPENSSL_assert(EVP_CIPHER_CTX_get_iv_length(ctx) == 16);
/* Now we can set key and IV */
if (!EVP_CipherInit_ex2(ctx, NULL, key, iv, do_encrypt, NULL)) {
/* Error */
EVP_CIPHER_CTX_free(ctx);
return 0;
}
for (;;) {
inlen = fread(inbuf, 1, 1024, in);
if (inlen <= 0)
break;
if (!EVP_CipherUpdate(ctx, outbuf, &outlen, inbuf, inlen)) {
/* Error */
EVP_CIPHER_CTX_free(ctx);
return 0;
}
fwrite(outbuf, 1, outlen, out);
}
if (!EVP_CipherFinal_ex(ctx, outbuf, &outlen)) {
/* Error */
EVP_CIPHER_CTX_free(ctx);
return 0;
}
fwrite(outbuf, 1, outlen, out);
EVP_CIPHER_CTX_free(ctx);
return 1;
}
Encryption using AES-CBC with a 256-bit key with "CS1" ciphertext
stealing.
int encrypt(const unsigned char *key, const unsigned char *iv,
const unsigned char *msg, size_t msg_len, unsigned char *out)
{
/*
* This assumes that key size is 32 bytes and the iv is 16 bytes.
* For ciphertext stealing mode the length of the ciphertext "out" will be
* the same size as the plaintext size "msg_len".
* The "msg_len" can be any size >= 16.
*/
int ret = 0, encrypt = 1, outlen, len;
EVP_CIPHER_CTX *ctx = NULL;
EVP_CIPHER *cipher = NULL;
OSSL_PARAM params[2];
ctx = EVP_CIPHER_CTX_new();
cipher = EVP_CIPHER_fetch(NULL, "AES-256-CBC-CTS", NULL);
if (ctx == NULL || cipher == NULL)
goto err;
/*
* The default is "CS1" so this is not really needed,
* but would be needed to set either "CS2" or "CS3".
*/
params[0] = OSSL_PARAM_construct_utf8_string(OSSL_CIPHER_PARAM_CTS_MODE,
"CS1", 0);
params[1] = OSSL_PARAM_construct_end();
if (!EVP_CipherInit_ex2(ctx, cipher, key, iv, encrypt, params))
goto err;
/* NOTE: CTS mode does not support multiple calls to EVP_CipherUpdate() */
if (!EVP_CipherUpdate(ctx, out, &outlen, msg, msg_len))
goto err;
if (!EVP_CipherFinal_ex(ctx, out + outlen, &len))
goto err;
ret = 1;
err:
EVP_CIPHER_free(cipher);
EVP_CIPHER_CTX_free(ctx);
return ret;
}
SEE ALSO
evp(7), property(7), "ALGORITHM FETCHING" in crypto(7),
provider-cipher(7), life_cycle-cipher(7)
Supported ciphers are listed in:
EVP_aes_128_gcm(3), EVP_aria_128_gcm(3), EVP_bf_cbc(3),
EVP_camellia_128_ecb(3), EVP_cast5_cbc(3), EVP_chacha20(3),
EVP_des_cbc(3), EVP_desx_cbc(3), EVP_idea_cbc(3), EVP_rc2_cbc(3),
EVP_rc4(3), EVP_rc5_32_12_16_cbc(3), EVP_seed_cbc(3), EVP_sm4_cbc(3),
HISTORY
Support for OCB mode was added in OpenSSL 1.1.0.
EVP_CIPHER_CTX was made opaque in OpenSSL 1.1.0. As a result,
EVP_CIPHER_CTX_reset() appeared and EVP_CIPHER_CTX_cleanup() disappeared.
EVP_CIPHER_CTX_init() remains as an alias for EVP_CIPHER_CTX_reset().
The EVP_CIPHER_CTX_cipher() function was deprecated in OpenSSL 3.0; use
EVP_CIPHER_CTX_get0_cipher() instead.
The EVP_EncryptInit_ex2(), EVP_DecryptInit_ex2(), EVP_CipherInit_ex2(),
EVP_CIPHER_fetch(), EVP_CIPHER_free(), EVP_CIPHER_up_ref(),
EVP_CIPHER_CTX_get0_cipher(), EVP_CIPHER_CTX_get1_cipher(),
EVP_CIPHER_get_params(), EVP_CIPHER_CTX_set_params(),
EVP_CIPHER_CTX_get_params(), EVP_CIPHER_gettable_params(),
EVP_CIPHER_settable_ctx_params(), EVP_CIPHER_gettable_ctx_params(),
EVP_CIPHER_CTX_settable_params() and EVP_CIPHER_CTX_gettable_params()
functions were added in 3.0.
The EVP_CIPHER_nid(), EVP_CIPHER_name(), EVP_CIPHER_block_size(),
EVP_CIPHER_key_length(), EVP_CIPHER_iv_length(), EVP_CIPHER_flags(),
EVP_CIPHER_mode(), EVP_CIPHER_type(), EVP_CIPHER_CTX_nid(),
EVP_CIPHER_CTX_block_size(), EVP_CIPHER_CTX_key_length(),
EVP_CIPHER_CTX_iv_length(), EVP_CIPHER_CTX_tag_length(),
EVP_CIPHER_CTX_num(), EVP_CIPHER_CTX_type(), and EVP_CIPHER_CTX_mode()
functions were renamed to include "get" or "get0" in their names in
OpenSSL 3.0, respectively. The old names are kept as non-deprecated alias
macros.
The EVP_CIPHER_CTX_encrypting() function was renamed to
EVP_CIPHER_CTX_is_encrypting() in OpenSSL 3.0. The old name is kept as
non-deprecated alias macro.
The EVP_CIPHER_CTX_flags() macro was deprecated in OpenSSL 1.1.0.
EVP_CIPHER_CTX_dup() was added in OpenSSL 3.2.
EVP_CipherInit_SKEY() was added in OpenSSL 3.5.
Prior to OpenSSL 3.5, passing a NULL ctx to
EVP_CIPHER_CTX_get_block_size() would result in a NULL pointer
dereference, rather than a 0 return value indicating an error.
COPYRIGHT
Copyright 2000-2026 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the Apache License 2.0 (the "License"). You may not use
this file except in compliance with the License. You can obtain a copy
in the file LICENSE in the source distribution or at
<https://www.openssl.org/source/license.html>.
3.6.5 2026-09-29 EVP_ENCRYPTINIT(3ossl)
openssl 3.6.5 - Generated Sat Oct 3 07:19:41 CDT 2026