mirror of
https://github.com/9fans/plan9port.git
synced 2025-01-12 11:10:07 +00:00
151 lines
3 KiB
Groff
151 lines
3 KiB
Groff
.TH SECHASH 3
|
|
.SH NAME
|
|
md4, md5, sha1, hmac_md5, hmac_sha1, md5pickle, md5unpickle, sha1pickle, sha1unpickle \- cryptographically secure hashes
|
|
.SH SYNOPSIS
|
|
.B #include <u.h>
|
|
.br
|
|
.B #include <libc.h>
|
|
.br
|
|
.B #include <mp.h>
|
|
.br
|
|
.B #include <libsec.h>
|
|
.PP
|
|
.B
|
|
DigestState* md4(uchar *data, ulong dlen, uchar *digest,
|
|
.B
|
|
DigestState *state)
|
|
.PP
|
|
.B
|
|
DigestState* md5(uchar *data, ulong dlen, uchar *digest,
|
|
.B
|
|
DigestState *state)
|
|
.PP
|
|
.B
|
|
char* md5pickle(MD5state *state)
|
|
.PP
|
|
.B
|
|
MD5state* md5unpickle(char *p);
|
|
.PP
|
|
.B
|
|
DigestState* sha1(uchar *data, ulong dlen, uchar *digest,
|
|
.B
|
|
DigestState *state)
|
|
.PP
|
|
.B
|
|
char* sha1pickle(MD5state *state)
|
|
.PP
|
|
.B
|
|
MD5state* sha1unpickle(char *p);
|
|
.PP
|
|
.B
|
|
DigestState* hmac_md5(uchar *data, ulong dlen,
|
|
.br
|
|
.B
|
|
uchar *key, ulong klen,
|
|
.br
|
|
.B
|
|
uchar *digest, DigestState *state)
|
|
.PP
|
|
.B
|
|
DigestState* hmac_sha1(uchar *data, ulong dlen,
|
|
.br
|
|
.B
|
|
uchar *key, ulong klen,
|
|
.br
|
|
.B
|
|
uchar *digest, DigestState *state)
|
|
.SH DESCRIPTION
|
|
.PP
|
|
These functions implement
|
|
the cryptographic hash functions MD4, MD5, and SHA1. The output of the
|
|
hash is called a
|
|
.IR digest .
|
|
A hash is secure if, given the hashed data and the digest,
|
|
it is difficult to predict the change to the digest resulting
|
|
from some change to the data without rehashing
|
|
the whole data. Therefore, if a secret is part of the hashed
|
|
data, the digest can be used as an integrity check of the data by anyone
|
|
possessing the secret.
|
|
.PP
|
|
The routines
|
|
.IR md4 ,
|
|
.IR md5 ,
|
|
.IR sha1 ,
|
|
.IR hmac_md5 ,
|
|
and
|
|
.I hmac_sha1
|
|
differ only in the length of the resulting digest
|
|
and in the security of the hash. Usage for each is the same.
|
|
The first call to the routine should have
|
|
.B nil
|
|
as the
|
|
.I state
|
|
parameter. This call returns a state which can be used to chain
|
|
subsequent calls.
|
|
The last call should have digest non-\fBnil\fR.
|
|
.I Digest
|
|
must point to a buffer of at least the size of the digest produced.
|
|
This last call will free the state and copy the result into
|
|
.IR digest .
|
|
For example, to hash a single buffer using
|
|
.IR md5 :
|
|
.EX
|
|
|
|
uchar digest[MD5dlen];
|
|
|
|
md5(data, len, digest, nil);
|
|
.EE
|
|
.PP
|
|
To chain a number of buffers together,
|
|
bounded on each end by some secret:
|
|
.EX
|
|
|
|
char buf[256];
|
|
uchar digest[MD5dlen];
|
|
DigestState *s;
|
|
|
|
s = md5("my password", 11, nil, nil);
|
|
while((n = read(fd, buf, 256)) > 0)
|
|
md5(buf, n, nil, s);
|
|
md5("drowssap ym", 11, digest, s);
|
|
.EE
|
|
.PP
|
|
The constants
|
|
.IR MD4dlen ,
|
|
.IR MD5dlen ,
|
|
and
|
|
.I SHA1dlen
|
|
define the lengths of the digests.
|
|
.PP
|
|
.I Hmac_md5
|
|
and
|
|
.I hmac_sha1
|
|
are used slightly differently. These hash algorithms are keyed and require
|
|
a key to be specified on every call.
|
|
The digest lengths for these hashes are
|
|
.I MD5dlen
|
|
and
|
|
.I SHA1dlen
|
|
respectively.
|
|
.PP
|
|
The functions
|
|
.I md5pickle
|
|
and
|
|
.I sha1pickle
|
|
marshal the state of a digest for transmission.
|
|
.I Md5unpickle
|
|
and
|
|
.I sha1unpickle
|
|
unmarshal a pickled digest.
|
|
All four routines return a pointer to a newly
|
|
.MR malloc (3) 'd
|
|
object.
|
|
.SH SOURCE
|
|
.B \*9/src/libsec
|
|
.SH SEE ALSO
|
|
.MR aes (3) ,
|
|
.MR blowfish (3) ,
|
|
.MR des (3) ,
|
|
.MR elgamal (3) ,
|
|
.MR rc4 (3) ,
|
|
.MR rsa (3)
|