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| <title>sechash(3) - Plan 9 from User Space</title> |
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| <tr><td width=20><td><b>SECHASH(3)</b><td align=right><b>SECHASH(3)</b> |
| <tr><td width=20><td colspan=2> |
| <br> |
| <p><font size=+1><b>NAME </b></font><br> |
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| md4, md5, sha1, hmac_md5, hmac_sha1, md5pickle, md5unpickle, sha1pickle, |
| sha1unpickle – cryptographically secure hashes<br> |
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| </table> |
| <p><font size=+1><b>SYNOPSIS </b></font><br> |
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| <tt><font size=+1>#include <u.h><br> |
| #include <libc.h><br> |
| #include <mp.h><br> |
| #include <libsec.h> |
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| </font></tt> |
| <tt><font size=+1>DigestState* md4(uchar *data, ulong dlen, uchar *digest, DigestState |
| *state) |
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| </font></tt> |
| <tt><font size=+1>DigestState* md5(uchar *data, ulong dlen, uchar *digest, DigestState |
| *state) |
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| </font></tt> |
| <tt><font size=+1>char* md5pickle(MD5state *state) |
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| </font></tt> |
| <tt><font size=+1>MD5state* md5unpickle(char *p); |
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| </font></tt> |
| <tt><font size=+1>DigestState* sha1(uchar *data, ulong dlen, uchar *digest, DigestState |
| *state) |
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| </font></tt> |
| <tt><font size=+1>char* sha1pickle(MD5state *state) |
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| </font></tt> |
| <tt><font size=+1>MD5state* sha1unpickle(char *p); |
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| </font></tt> |
| <tt><font size=+1>DigestState* hmac_md5(uchar *data, ulong dlen,<br> |
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| uchar *key, ulong klen,<br> |
| uchar *digest, DigestState *state) |
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| |
| </table> |
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| </table> |
| </font></tt> |
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| </table> |
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| </table> |
| <tt><font size=+1>DigestState* hmac_sha1(uchar *data, ulong dlen,<br> |
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| uchar *key, ulong klen,<br> |
| uchar *digest, DigestState *state)<br> |
| |
| </table> |
| |
| </table> |
| </font></tt> |
| </table> |
| <p><font size=+1><b>DESCRIPTION </b></font><br> |
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| These functions implement the cryptographic hash functions MD4, |
| MD5, and SHA1. The output of the hash is called a <i>digest</i>. 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. |
| |
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| The routines <i>md4</i>, <i>md5</i>, <i>sha1</i>, <i>hmac_md5</i>, and <i>hmac_sha1</i> 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 <tt><font size=+1>nil</font></tt> as the <i>state</i> parameter. This call returns a state |
| which can be used to chain subsequent calls. The last call |
| should have digest non-nil. <i>Digest</i> 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 <i>digest</i>. For example, to hash |
| a single buffer using <i>md5</i>:<br> |
| |
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| <tt><font size=+1>uchar digest[MD5dlen];<br> |
| md5(data, len, digest, nil);<br> |
| |
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| </font></tt> |
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| </table> |
| To chain a number of buffers together, bounded on each end by |
| some secret:<br> |
| |
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| |
| <tt><font size=+1>char buf[256];<br> |
| uchar digest[MD5dlen];<br> |
| DigestState *s;<br> |
| s = md5("my password", 11, nil, nil);<br> |
| while((n = read(fd, buf, 256)) > 0)<br> |
| |
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| md5(buf, n, nil, s);<br> |
| |
| </table> |
| md5("drowssap ym", 11, digest, s);<br> |
| |
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| </font></tt> |
| |
| </table> |
| The constants <i>MD4dlen</i>, <i>MD5dlen</i>, and <i>SHA1dlen</i> define the lengths |
| of the digests. |
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| |
| <i>Hmac_md5</i> and <i>hmac_sha1</i> 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</i> and <i>SHA1dlen</i> |
| respectively. |
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| The functions <i>md5pickle</i> and <i>sha1pickle</i> marshal the state of a |
| digest for transmission. <i>Md5unpickle</i> and <i>sha1unpickle</i> unmarshal |
| a pickled digest. All four routines return a pointer to a newly |
| <a href="../man3/malloc.html"><i>malloc</i>(3)</a>’d object.<br> |
| |
| </table> |
| <p><font size=+1><b>SOURCE </b></font><br> |
| |
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| |
| <tt><font size=+1>/usr/local/plan9/src/libsec<br> |
| </font></tt> |
| </table> |
| <p><font size=+1><b>SEE ALSO </b></font><br> |
| |
| <table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td> |
| |
| <a href="../man3/aes.html"><i>aes</i>(3)</a>, <a href="../man3/blowfish.html"><i>blowfish</i>(3)</a>, <a href="../man3/des.html"><i>des</i>(3)</a>, <a href="../man3/elgamal.html"><i>elgamal</i>(3)</a>, <a href="../man3/rc4.html"><i>rc4</i>(3)</a>, <a href="../man3/rsa.html"><i>rsa</i>(3)</a><br> |
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