`GCRY_MD_NONE`

- This is not a real algorithm but used by some functions as an error
return value. This constant is guaranteed to have the value
`0`

. `GCRY_MD_SHA1`

- This is the SHA-1 algorithm which yields a message digest of 20 bytes.
`GCRY_MD_RMD160`

- This is the 160 bit version of the RIPE message digest (RIPE-MD-160).
Like SHA-1 it also yields a digest of 20 bytes.
`GCRY_MD_MD5`

- This is the well known MD5 algorithm, which yields a message digest of
16 bytes.
`GCRY_MD_MD4`

- This is the MD4 algorithm, which yields a message digest of 16 bytes.
`GCRY_MD_MD2`

- This is an reserved identifier for MD-2; there is no implementation yet.
`GCRY_MD_TIGER`

- This is the TIGER/192 algorithm which yields a message digest of 24 bytes.
`GCRY_MD_HAVAL`

- This is an reserved for the HAVAL algorithm with 5 passes and 160
bit. It yields a message digest of 20 bytes. Note that there is no
implementation yet available.
`GCRY_MD_SHA224`

- This is the SHA-224 algorithm which yields a message digest of 28 bytes.
See Change Notice 1 for FIPS 180-2 for the specification.
`GCRY_MD_SHA256`

- This is the SHA-256 algorithm which yields a message digest of 32 bytes.
See FIPS 180-2 for the specification.
`GCRY_MD_SHA384`

- This is the SHA-384 algorithm which yields a message digest of 48 bytes.
See FIPS 180-2 for the specification.
`GCRY_MD_SHA512`

- This is the SHA-384 algorithm which yields a message digest of 64 bytes.
See FIPS 180-2 for the specification.
`GCRY_MD_CRC32`

- This is the ISO 3309 and ITU-T V.42 cyclic redundancy check. It
yields an output of 4 bytes.
`GCRY_MD_CRC32_RFC1510`

- This is the above cyclic redundancy check function, as modified by RFC
1510. It yields an output of 4 bytes.
`GCRY_MD_CRC24_RFC2440`

- This is the OpenPGP cyclic redundancy check function. It yields an
output of 3 bytes.
`GCRY_MD_WHIRLPOOL`

- This is the Whirlpool algorithm which yields a message digest of 64 bytes.