EVP_PKEY-SLH-DSA(7ossl) OpenSSL EVP_PKEY-SLH-DSA(7ossl)
NAME
EVP_PKEY-SLH-DSA, EVP_KEYMGMT-SLH-DSA, EVP_PKEY-SLH-DSA-SHA2-128s,
EVP_PKEY-SLH-DSA-SHA2-128f, EVP_PKEY-SLH-DSA-SHA2-192s,
EVP_PKEY-SLH-DSA-SHA2-192f, EVP_PKEY-SLH-DSA-SHA2-256s,
EVP_PKEY-SLH-DSA-SHA2-256f, EVP_PKEY-SLH-DSA-SHAKE-128s,
EVP_PKEY-SLH-DSA-SHAKE-128f, EVP_PKEY-SLH-DSA-SHAKE-192s,
EVP_PKEY-SLH-DSA-SHAKE-192f, EVP_PKEY-SLH-DSA-SHAKE-256s,
EVP_PKEY-SLH-DSA-SHAKE-256f - EVP_PKEY SLH-DSA keytype and algorithm
support
DESCRIPTION
The SLH-DSA-SHA2-128s, EVP_PKEY-SLH-DSA-SHA2-128f, SLH-DSA-SHA2-192s,
EVP_PKEY-SLH-DSA-SHA2-192f, SLH-DSA-SHA2-256s,
EVP_PKEY-SLH-DSA-SHA2-256f, SLH-DSA-SHAKE-128s,
EVP_PKEY-SLH-DSA-SHAKE-128f, SLH-DSA-SHAKE-192s,
EVP_PKEY-SLH-DSA-SHAKE-192f, SLH-DSA-SHAKE-256s and
EVP_PKEY-SLH-DSA-SHAKE-256f key types are implemented in OpenSSL's
default and FIPS providers. These implementations support the associated
key, containing the public key pub and the private key priv.
SLH-DSA (Stateless Hash-based Digital Signature Standard) uses small
keys, but has relatively large signatures and is relatively slow
performing all operations compared to ML-DSA. It does however have proven
security proofs, since it relies only on hash functions.
Each of the different key types has an associated security parameter n.
This value is one of 16, 24 or 32 for key types SLH-DSA*128*,
SLH-DSA*192* and SLH-DSA*256*, respectively.
Both the public and private key components contain 2 elements of size n.
Key generation generates the private key elements and one of the public
key elements randomly, and the final public key element is computed from
these values.
The public key has relatively small sizes of 32, 48 or 64 bytes,
corresponding to the algorithm names of 128, 192 and 256 respectively.
The algorithms ending with s produce smaller signatures, but are much
slower than the faster f variants.
The signature sizes for the s algorithm variants are 7856, 16224 and
29792 which correspond to the algorithm names of 128s, 192s and 256s
respectively. The signature sizes for the f algorithm variants are
17088, 35664 and 49856 which correspond to the algorithm names containing
128f, 192f and 256f respectively.
Internally there are 7 hash related functions that are used for each
algorithm. For algorithms containing SHAKE in their name SHAKE-256 is
used for all functions. For the <SHA2-128> algorithms the functions use
<MGF1-SHA-256>, <HMAC-SHA-256> and <SHA-256>. The remaining <SHA2>
algorithms use <MGF1-SHA-512>, <HMAC-SHA-512>, <SHA-256> and <SHA-512>.
See FIPS 205 Section 11.1 and 11.2 for more information.
Keygen Parameters
"seed" (OSSL_PKEY_PARAM_SLH_DSA_SEED) <octet string>
Supplies values to use for the private seed, private prf and public
seed instead of generating random values. This is used for testing
purposes only. The length of the value supplied must be 3 * n.
"properties" (OSSL_PKEY_PARAM_PROPERTIES) <utf8_string>
Sets properties to be used when fetching algorithm implementations
used for SLH-DSA hashing operations.
Use EVP_PKEY_CTX_set_params() after calling EVP_PKEY_keygen_init().
The following key generation parameter can be retrieved with
EVP_PKEY_CTX_get_params(3) from the OpenSSL FIPS provider:
"fips-indicator" (OSSL_PKEY_PARAM_FIPS_APPROVED_INDICATOR) <integer>
Returns 1 if the operation is FIPS approved, or 0 otherwise. See
"FIPS indicators" in fips_module(7) for more information.
Common SLH-DSA parameters
In addition to the common parameters that all keytypes should support
(see "Common Information Parameters" in provider-keymgmt(7)), the
implementation of these key types support the following.
The following parameters are gettable using
EVP_PKEY_get_octet_string_param(), and settable when using
EVP_PKEY_fromdata().
"pub" (OSSL_PKEY_PARAM_PUB_KEY) <octet string>
The public key has a size of 2 * n bytes. i.e. It consists of the
concatenation of PK.seed and PK.root as defined by FIPS 205 Figure
16.
"priv" (OSSL_PKEY_PARAM_PRIV_KEY) <octet string>
The private key has a size of 4 * n bytes, which includes the public
key components. i.e. It consists of the concatenation of SK.seed,
SK.prf, PK.seed and PF.root as defined by FIPS 205 Figure 15.
"mandatory-digest" (OSSL_PKEY_PARAM_MANDATORY_DIGEST) <UTF8 string>
The empty string, signifying that no digest may be specified.
CONFORMING TO
FIPS 205
EXAMPLES
An EVP_PKEY context can be obtained by calling:
EVP_PKEY_CTX *pctx =
EVP_PKEY_CTX_new_from_name(NULL, "SLH-DSA-SHA2-128f", NULL);
An SLH-DSA key can be generated like this:
pkey = EVP_PKEY_Q_keygen(NULL, NULL, "SLH-DSA-SHA2-128f");
The key pair components can be extracted from a key by calling:
uint8_t priv[64], pub[32];
size_t priv_len, pub_len;
EVP_PKEY_get_octet_string_param(pkey, OSSL_PKEY_PARAM_PRIV_KEY,
priv, sizeof(priv), &priv_len);
EVP_PKEY_get_octet_string_param(pkey, OSSL_PKEY_PARAM_PUB_KEY,
pub, sizeof(pub), &pub_len));
Similar code can be used for the other key types such as
"SLH-DSA-SHAKE-256f".
SEE ALSO
EVP_KEYMGMT(3), EVP_PKEY(3), provider-keymgmt(7),
EVP_SIGNATURE-SLH-DSA(7)
HISTORY
This functionality was added in OpenSSL 3.5.
COPYRIGHT
Copyright 2024-2026 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_PKEY-SLH-DSA(7ossl)
openssl 3.6.5 - Generated Sat Oct 3 09:28:32 CDT 2026