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4.1 Public Key Algorithms
=========================

Public key algorithms are used for encryption, decryption, signing and
verification of signatures.

 -- Data type: enum gpgme_pubkey_algo_t
     The ‘gpgme_pubkey_algo_t’ type specifies the set of all public key
     algorithms that are supported by GPGME.  Possible values are:

     ‘GPGME_PK_RSA’
          This value indicates the RSA (Rivest, Shamir, Adleman)
          algorithm.

     ‘GPGME_PK_RSA_E’
          Deprecated.  This value indicates the RSA (Rivest, Shamir,
          Adleman) algorithm for encryption and decryption only.

     ‘GPGME_PK_RSA_S’
          Deprecated.  This value indicates the RSA (Rivest, Shamir,
          Adleman) algorithm for signing and verification only.

     ‘GPGME_PK_DSA’
          This value indicates DSA, the Digital Signature Algorithm.

     ‘GPGME_PK_ELG’
          This value indicates ElGamal.

     ‘GPGME_PK_ELG_E’
          This value also indicates ElGamal and is used specifically in
          GnuPG.

     ‘GPGME_PK_ECC’
          SINCE: 1.5.0

          This value is a generic indicator for ellipic curve
          algorithms.

     ‘GPGME_PK_ECDSA’
          SINCE: 1.3.0

          This value indicates ECDSA, the Elliptic Curve Digital
          Signature Algorithm as defined by FIPS 186-2 and RFC-6637.

     ‘GPGME_PK_ECDH’
          SINCE: 1.3.0

          This value indicates ECDH, the Eliptic Curve Diffie-Hellmann
          encryption algorithm as defined by RFC-6637.

     ‘GPGME_PK_EDDSA’
          SINCE: 1.7.0

          This value indicates the EdDSA algorithm.

 -- Function: const char * gpgme_pubkey_algo_name
          (gpgme_pubkey_algo_t ALGO)
     The function ‘gpgme_pubkey_algo_name’ returns a pointer to a
     statically allocated string containing a description of the public
     key algorithm ALGO.  This string can be used to output the name of
     the public key algorithm to the user.

     If ALGO is not a valid public key algorithm, ‘NULL’ is returned.

 -- Function: char * gpgme_pubkey_algo_string (gpgme_subkey_t KEY)
     SINCE: 1.7.0

     The function ‘gpgme_pubkey_algo_string’ is a convenience function
     to build and return an algorithm string in the same way GnuPG does
     (e.g., “rsa2048” or “ed25519”).  The caller must free the result
     using ‘gpgme_free’.  On error (e.g., invalid argument or memory
     exhausted), the function returns NULL and sets ‘ERRNO’.