term% cat index.txt SECHASH(2) System Calls Manual SECHASH(2)
NAME
md4, md5, sha1, sha2_224, sha2_256, sha2_384, sha2_512, aes, hmac_x,
hmac_md5, hmac_sha1, hmac_sha2_224, hmac_sha2_256, hmac_sha2_384,
hmac_sha2_512, hmac_aes, md5pickle, md5unpickle, sha1pickle, sha1un‐
pickle - cryptographically secure hashes
SYNOPSIS
#include <u.h>
#include <libc.h>
#include <mp.h>
#include <libsec.h>
#define DS DigestState /* only to abbreviate SYNOPSIS */
DS* md4(uchar *data, ulong dlen, uchar *digest, DS *state)
DS* md5(uchar *data, ulong dlen, uchar *digest, DS *state)
char* md5pickle(MD5state *state)
MD5state* md5unpickle(char *p);
DS* sha1(uchar *data, ulong dlen, uchar *digest, DS *state)
char* sha1pickle(SHA1state *state)
SHA1state* sha1unpickle(char *p);
DS* sha2_224(uchar *data, ulong dlen, uchar *digest, DS *state)
DS* sha2_256(uchar *data, ulong dlen, uchar *digest, DS *state)
DS* sha2_384(uchar *data, ulong dlen, uchar *digest, DS *state)
DS* sha2_512(uchar *data, ulong dlen, uchar *digest, DS *state)
DS* aes(uchar *data, ulong dlen, uchar *digest, DS *state)
DS* hmac_x(uchar *p, ulong len, uchar *key, ulong klen, uchar *digest,
DS *s, DS*(*x)(uchar*, ulong, uchar*, DS*), int xlen)
DS* hmac_md5(uchar *data, ulong dlen, uchar *key, ulong klen, uchar
*digest, DS *state)
DS* hmac_sha1(uchar *data, ulong dlen, uchar *key, ulong klen, uchar
*digest, DS *state)
DS* hmac_sha2_224(uchar *data, ulong dlen, uchar *key, ulong klen,
uchar *digest, DS *state)
DS* hmac_sha2_256(uchar *data, ulong dlen, uchar *key, ulong klen,
uchar *digest, DS *state)
DS* hmac_sha2_384(uchar *data, ulong dlen, uchar *key, ulong klen,
uchar *digest, DS *state)
DS* hmac_sha2_512(uchar *data, ulong dlen, uchar *key, ulong klen,
uchar *digest, DS *state)
DS* hmac_aes(uchar *data, ulong dlen, uchar *key, ulong klen, uchar
*digest, DS *state)
DESCRIPTION
We support several secure hash functions. The output of a hash is
called a 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.
The routines md4, md5, sha1, sha2_224, sha2_256, sha2_384, sha2_512,
aes, hmac_md5, hmac_sha1, hmac_sha2_224, hmac_sha2_256, hmac_sha2_384,
hmac_sha2_512, and hmac_aes differ only in the length of the resulting
digest and in the security of the hash. Sha2_* and hmac_sha2_* are the
SHA-2 functions; the number after the final underscore is the number of
bits in the resulting digest. Usage for each is the same. The first
call to the routine should have nil as the state parameter. This call
returns a state which can be used to chain subsequent calls. The last
call should have digest 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 digest.
The constants MD4dlen, MD5dlen, SHA1dlen, SHA2_224dlen, SHA2_256dlen,
SHA2_384dlen, SHA2_512dlen, and AESdlen define the lengths of the
digests.
Hmac_md5, hmac_sha1, hmac_sha2_224, hmac_sha2_256, hmac_sha2_384,
hmac_sha2_512, and hmac_aes 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 the obvious ones from the above
list of length constants. These routines all call hmac_x internally,
but hmac_x is not intended for general use.
The functions md5pickle and sha1pickle marshal the state of a digest
for transmission. Md5unpickle and sha1unpickle unmarshal a pickled
digest. All four routines return a pointer to a newly malloc(2)'d
object.
EXAMPLES
To hash a single buffer using md5:
uchar digest[MD5dlen];
md5(data, len, digest, nil);
To chain a number of buffers together, bounded on each end by some se‐
cret:
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);
SOURCE
/sys/src/libsec
SEE ALSO
aes(2), blowfish(2), des(2), elgamal(2), rc4(2), rsa(2)
/lib/rfc/rfc2104
HMAC specification
SECHASH(2)