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NAME
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md4, md5, sha1, hmac_md5, hmac_sha1, md5pickle, md5unpickle, sha1pickle,
sha1unpickle – cryptographically secure hashes
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SYNOPSIS
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#include <u.h>
#include <libc.h>
#include <mp.h>
#include <libsec.h>
DigestState* md4(uchar *data, ulong dlen, uchar *digest, DigestState
*state)
DigestState* md5(uchar *data, ulong dlen, uchar *digest, DigestState
*state)
char* md5pickle(MD5state *state)
MD5state* md5unpickle(char *p);
DigestState* sha1(uchar *data, ulong dlen, uchar *digest, DigestState
*state)
char* sha1pickle(MD5state *state)
MD5state* sha1unpickle(char *p);
DigestState* hmac_md5(uchar *data, ulong dlen,
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uchar *key, ulong klen,
uchar *digest, DigestState *state)
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DigestState* hmac_sha1(uchar *data, ulong dlen,
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uchar *key, ulong klen,
uchar *digest, DigestState *state)
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DESCRIPTION
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These functions implement the cryptographic hash functions MD4,
MD5, and SHA1. The output of the 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, hmac_md5, and 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 nil as the state parameter. This call returns a state
which can be used to chain subsequent calls. The last call should
have digest non-nil.
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. For example, to hash a single buffer using md5:
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uchar digest[MD5dlen];
md5(data, len, digest, nil);
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To chain a number of buffers together, bounded on each end by
some secret:
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char buf[256];
uchar digest[MD5dlen];
DigestState *s;
s = md5("my password", 11, nil, nil);
while((n = read(fd, buf, 256)) > 0)
md5("drowssap ym", 11, digest, s);
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The constants MD4dlen, MD5dlen, and SHA1dlen define the lengths
of the digests.
Hmac_md5 and 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 MD5dlen and SHA1dlen
respectively.
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(3)’d object.
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SOURCE
SEE ALSO
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