shithub: purgatorio

ref: f5cc6fbe3a7bcf8bdb002c646ddd519014afafd2
dir: /man/2/crypt-sha1/

.TH CRYPT-SHA1 2
.SH NAME
crypt: sha1, sha224, sha256, sha384, sha512, md4, md5, hmac_sha1, hmac_md5 \- cryptographic digests
.SH SYNOPSIS
.EX
include "ipints.m";
ipints := load IPints IPints->PATH;
IPint: import ipints;

include "crypt.m";
crypt := load Crypt Crypt->PATH;

DigestState: adt
{
    # hidden state
    copy:   fn(d: self ref DigestState): ref DigestState;
};

.ta \w'verify:\ 'u +\w'fn(\ \ \ 'u
sha1:	fn(buf: array of byte, n: int, digest: array of byte,
		state: ref DigestState): ref DigestState;
sha224:	fn(buf: array of byte, n: int, digest: array of byte,
		state: ref DigestState): ref DigestState;
sha256:	fn(buf: array of byte, n: int, digest: array of byte,
		state: ref DigestState): ref DigestState;
sha384:	fn(buf: array of byte, n: int, digest: array of byte,
		state: ref DigestState): ref DigestState;
sha512:	fn(buf: array of byte, n: int, digest: array of byte,
		state: ref DigestState): ref DigestState;
md4:	fn(buf: array of byte, n: int, digest: array of byte,
		state: ref DigestState): ref DigestState;
md5:	fn(buf: array of byte, n: int, digest: array of byte,
		state: ref DigestState): ref DigestState;

SHA1dlen, SHA224dlen, SHA256dlen, SHA384dlen, SHA512dlen, MD4dlen, MD5dlen: con ...;

hmac_sha1: fn(buf: array of byte, n: int, key: array of byte,
		    digest: array of byte,
		    state: ref DigestState): ref DigestState;
hmac_md5:  fn(buf: array of byte, n: int, key: array of byte,
		    digest: array of byte,
		    state: ref DigestState): ref DigestState;
.EE
.SH DESCRIPTION
.BR Sha1 ,
.BR sha224 ,
.BR sha256 ,
.BR sha384 ,
.BR sha512 ,
.B md4
and
.B md5
are cryptographically secure hash functions that produce output called a message digest.
Each function computes a hash of
.I n
bytes of the data in
.IR buf ,
using the named algorithm,
and updates the current
.IR state .
They can be called iteratively to form a single digest for many data blocks.
The state is kept in the
.B DigestState
value referenced by
.I state
between calls.
.I State
should be
.B nil
on the first call, and a newly allocated
.B DigestState
will be returned for use in subsequent calls.
On a call in which
.I digest
is not
.BR nil ,
the hash is completed and copied into the
.I digest
array.
.B Sha1
produces a 20-byte hash
.RB ( SHA1dlen ),
.B sha224
a 28-byte hash
.RB ( SHA224dlen ),
.B sha256
a 32-byte hash
.RB ( SHA256dlen ),
.B sha384
a 48-byte hash
.RB ( SHA384dlen ),
.B sha256
a 64-byte hash
.RB ( SHA512dlen ),
.B md4
and
.B md5
a 16-byte one
.RB ( MD4len
and
.BR MD5len ).
.PP
.B Hmac_sha1
and
.B hmac_md5
are keyed versions of the hashing functions, following Internet RFC2104.
The
.I key
must be provided in each call, but otherwise
the calling conventions are those of
.BR sha1 .
The
.I key
must currently be no more than 64 bytes.
.PP
.B DigestState
hides the state of partially completed hash functions during processing.
Its
.B copy
operation returns a reference to a new copy of a given state.
.SH EXAMPLES
A program to read a file and hash it using SHA might contain the following inner loop:
.IP
.EX
state: ref DigestState = nil;
while((n := sys->read(fd, buf, len buf)) > 0)
	state = kr->sha1(buf, n, nil, state);
digest := array[kr->SHA1dlen] of byte;
kr->sha1(buf, 0, digest, state);
.EE
.SH SOURCE
.B /libinterp/crypt.c
.br
.B /libsec/port/hmac.c
.br
.B /libsec/port/md4.c
.br
.B /libsec/port/md5.c
.br
.B /libsec/port/sha1.c
.SH BUGS
The MD4 algorithm is included only to allow communication with software
that might still use it; it should not otherwise be used now, because it
is easily broken.