The Hash module implements unkeyed cryptographic hashes (SHA-1, SHA-256, SHA-512, SHA-3, RIPEMD-160 and MD5), also known as message digest functions. Hash functions used in cryptography are characterized as being one-way (given a hash value, it is computationally infeasible to find a text that hashes to this value) and collision-resistant (it is computationally infeasible to find two different texts that hash to the same value). Thus, the hash of a text can be used as a compact replacement for this text for the purposes of ensuring integrity of the text.
val sha3 : int -> hashSHA-3, the latest NIST standard for cryptographic hashing, produces hashes of 224, 256, 384 or 512 bits (24, 32, 48 or 64 bytes). The parameter is the desired size of the hash, in bits. It must be one of 224, 256, 384 or 512.
val keccak : int -> hashThe Keccak submission for the SHA-3 is very similar to sha3 but uses a slightly different padding. The parameter is the same as that of sha3.
val sha2 : int -> hashSHA-2, another NIST standard for cryptographic hashing, produces hashes of 224, 256, 384, or 512 bits (24, 32, 48 or 64 bytes). The parameter is the desired size of the hash, in bits. It must be one of 224, 256, 384 or 512.
val sha224 : unit -> hashSHA-224 is SHA-2 specialized to 224 bit hashes (24 bytes).
val sha256 : unit -> hashSHA-256 is SHA-2 specialized to 256 bit hashes (32 bytes).
val sha384 : unit -> hashSHA-384 is SHA-2 specialized to 384 bit hashes (48 bytes).
val sha512 : unit -> hashSHA-512 is SHA-2 specialized to 512 bit hashes (64 bytes).
val blake2b : int -> hashThe BLAKE2b hash function produces hashes of length 1 to 64 bytes. The parameter is the desired size of the hash, in bits. It must be between 8 and 512, and a multiple of 8.
val blake2b512 : unit -> hashBLAKE2b512 is BLAKE2b specialized to 512 bit hashes (64 bytes).
val blake2s : int -> hashThe BLAKE2s hash function produces hashes of length 1 to 32 bytes. The parameter is the desired size of the hash, in bits. It must be between 8 and 256, and a multiple of 8.
val blake2s256 : unit -> hashBLAKE2s256 is BLAKE2s specialized to 256 bit hashes (32 bytes).
val ripemd160 : unit -> hashRIPEMD-160 produces 160-bit hashes (20 bytes).
val sha1 : unit -> hashSHA-1 is the Secure Hash Algorithm revision 1. It is a NIST standard, is widely used, and produces 160-bit hashes (20 bytes). While popular in many legacy applications, it is now known to be insecure. In particular, it is not collision-resistant.
val md5 : unit -> hashMD5 is an older hash function, producing 128-bit hashes (16 bytes). While popular in many legacy applications, it is now known to be insecure. In particular, it is not collision-resistant.