( General cipher functions

Info Catalog ( Working with cipher handles ( Symmetric cryptography
 5.5 General cipher functions
 To work with the algorithms, several functions are available to map
 algorithm names to the internal identifiers, as well as ways to
 retrieve information about an algorithm or the current cipher context.
  -- Function: gcry_error_t gcry_cipher_algo_info (int ALGO, int WHAT,
           void *BUFFER, size_t *NBYTES)
      This function is used to retrieve information on a specific
      algorithm.  You pass the cipher algorithm ID as ALGO and the type
      of information requested as WHAT. The result is either returned as
      the return code of the function or copied to the provided BUFFER
      whose allocated length must be available in an integer variable
      with the address passed in NBYTES.  This variable will also
      receive the actual used length of the buffer.
      Here is a list of supported codes for WHAT:
           Return the length of the key. If the algorithm supports
           multiple key lengths, the maximum supported value is
           returned.  The length is returned as number of octets (bytes)
           and not as number of bits in NBYTES; BUFFER must be zero.
           Return the block length of the algorithm.  The length is
           returned as a number of octets in NBYTES; BUFFER must be zero.
           Returns `0' when the specified algorithm is available for use.
           BUFFER and NBYTES must be zero.
  -- Function: const char *gcry_cipher_algo_name (int ALGO)
      `gcry_cipher_algo_name' returns a string with the name of the
      cipher algorithm ALGO.  If the algorithm is not known or another
      error occurred, an empty string is returned.  This function will
      never return `NULL'.
  -- Function: int gcry_cipher_map_name (const char *NAME)
      `gcry_cipher_map_name' returns the algorithm identifier for the
      cipher algorithm described by the string NAME.  If this algorithm
      is not available `0' is returned.
  -- Function: int gcry_cipher_mode_from_oid (const char *STRING)
      Return the cipher mode associated with an ASN.1 object identifier.
      The object identifier is expected to be in the IETF-style dotted
      decimal notation.  The function returns `0' for an unknown object
      identifier or when no mode is associated with it.
Info Catalog ( Working with cipher handles ( Symmetric cryptography
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