Digest.3o - Man Page
Message digest.
Module
Module Digest
Documentation
Module Digest
: sig end
Message digest.
This module provides functions to compute 'digests', also known as 'hashes', of arbitrary-length strings or files. The supported hashing algorithms are BLAKE2 and MD5.
Basic functions
The functions in this section use the MD5 hash function to produce 128-bit digests (16 bytes). MD5 is not cryptographically secure. Hence, these functions should not be used for security-sensitive applications. The BLAKE2 functions below are cryptographically secure.
type t = string
The type of digests: 16-byte strings.
val compare : t -> t -> int
The comparison function for 16-byte digests, with the same specification as compare and the implementation shared with String.compare . Along with the type t , this function compare allows the module Digest to be passed as argument to the functors Set.Make and Map.Make .
Since 4.00
val equal : t -> t -> bool
The equal function for 16-byte digests.
Since 4.03
val string : string -> t
Return the digest of the given string.
val bytes : bytes -> t
Return the digest of the given byte sequence.
Since 4.02
val substring : string -> int -> int -> t
Digest.substring s ofs len returns the digest of the substring of s starting at index ofs and containing len characters.
val subbytes : bytes -> int -> int -> t
Digest.subbytes s ofs len returns the digest of the subsequence of s starting at index ofs and containing len bytes.
Since 4.02
val channel : in_channel -> int -> t
If len is nonnegative, Digest.channel ic len reads len characters from channel ic and returns their digest, or raises End_of_file if end-of-file is reached before len characters are read. If len is negative, Digest.channel ic len reads all characters from ic until end-of-file is reached and return their digest.
val file : string -> t
Return the digest of the file whose name is given.
val output : out_channel -> t -> unit
Write a digest on the given output channel.
val input : in_channel -> t
Read a digest from the given input channel.
val to_hex : t -> string
Return the printable hexadecimal representation of the given digest.
Raises Invalid_argument if the argument is not exactly 16 bytes.
val of_hex : string -> t
Convert a hexadecimal representation back into the corresponding digest.
Since 5.2
Raises Invalid_argument if the argument is not exactly 32 hexadecimal characters.
val from_hex : string -> t
Same function as Digest.of_hex .
Since 4.00
Generic interface
module type S = sig end
The signature for a hash function that produces digests of length hash_length from character strings, byte arrays, and files.
Since 5.2
Specific hash functions
module BLAKE128 : S
BLAKE128 is the BLAKE2b hash function producing 128-bit (16-byte) digests. It is cryptographically secure. However, the small size of the digests enables brute-force attacks in 2{^64} attempts.
Since 5.2
module BLAKE256 : S
BLAKE256 is the BLAKE2b hash function producing 256-bit (32-byte) digests. It is cryptographically secure, and the digests are large enough to thwart brute-force attacks.
Since 5.2
module BLAKE512 : S
BLAKE512 is the BLAKE2b hash function producing 512-bit (64-byte) digests. It is cryptographically secure, and the digests are large enough to thwart brute-force attacks.
Since 5.2
module MD5 : S
MD5 is the MD5 hash function. It produces 128-bit (16-byte) digests and is not cryptographically secure at all. It should be used only for compatibility with earlier designs that mandate the use of MD5.
Since 5.2