3.5.1 Hashes of data and files

The most important predicates to compute hashes are:

[det]crypto_data_hash(+Data, -Hash, +Options)

Hash is the hash of Data. The conversion is controlled by Options:

algorithm(+Algorithm)

One of md5 (insecure), sha1 (insecure), ripemd160, sha224, sha256, sha384, sha512, sha3_224, sha3_256, sha3_384, sha3_512, blake2s256 or blake2b512. The BLAKE digest algorithms require OpenSSL 1.1.0 or greater, and the SHA-3 algorithms require OpenSSL 1.1.1 or greater. The default is a cryptographically secure algorithm. If you specify a variable, then that variable is unified with the algorithm that was used.

encoding(+Encoding)

If Data is a sequence of character codes, this must be translated into a sequence of bytes, because that is what the hashing requires. The default encoding is utf8. The other meaningful value is octet, claiming that Data contains raw bytes.

hmac(+Key)

If this option is specified, a hash-based message authentication code (HMAC) is computed, using the specified Key which is either an atom, string or list of bytes. Any of the available digest algorithms can be used with this option. The cryptographic strength of the HMAC depends on that of the chosen algorithm and also on the key. This option requires OpenSSL 1.1.0 or greater.

Data	is either an atom, string or code-list
Hash	is an atom that represents the hash in hexadecimal encoding.

See also

- hex_bytes/2 for conversion between hexadecimal encoding and lists of bytes.
- crypto_password_hash/2 for the important use case of passwords.

[det]crypto_file_hash(+File, -Hash, +Options)

True if Hash is the hash of the content of File. For Options, see crypto_data_hash/3.