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<h1> The <tt>stdcrypto</tt> library interface </h1>
<p>
<tt>stdcrypto</tt> is a small collection of standard,
public-domain cryptographic primitives. Currently, the following
operations are provided:
</p>
<ul>
<li> rc4 </li>
<li> md5 </li>
<li> sha1 </li>
</ul>
<h2> Compiling </h2>
<ul>
<li> Use <tt>#include <skalibs/stdcrypto.h></tt> </li>
</ul>
<h2> Programming </h2>
<p>
You should refer to the <tt>skalibs/stdcrypto.h</tt> header and included headers
for the exact function prototypes.
</p>
<h3> <a name="rc4" />
RC4 </h3>
<pre>
RC4Schedule ctx ;
unsigned char const *key ;
unsigned int keylen ;
unsigned char const *in ;
unsigned char *out ;
unsigned int len ;
rc4_init(&ctx, key, keylen) ;
rc4(&ctx, in, out, len) ;
</pre>
<ul>
<li> <tt>rc4_init()</tt> initializes a RC4Schedule structure with a key <em>key</em>,
of length <em>keylen</em>. It then computes and throws away the first <tt>RC4_THROWAWAY</tt>
bytes, usually 100 </li>
<li> <tt>rc4()</tt> encrypts <em>len</em> bytes of <em>in</em> with the RC4 flow, and
stores the results into <em>out</em> </li>
</ul>
<h3> <a name="md5" />
MD5 </h3>
<pre>
MD5Schedule ctx ;
char const *message ;
unsigned int messagelen ;
char digest[16] ;
md5_init(&ctx) ;
md5_update(&ctx, message, messagelen) ;
md5_final(&ctx, digest) ;
</pre>
<ul>
<li> <tt>md5_init()</tt> prepares a MD5Schedule structure for computation </li>
<li> <tt>md5_update()</tt> adds <em>message</em> to the message to be digested </li>
<li> <tt>md5_final()</tt> computes the digest </li>
</ul>
<h3> <a name="sha1"></a>
SHA1 </h3>
<pre>
SHA1Schedule ctx ;
char const *message ;
unsigned int messagelen ;
unsigned char digest[20] ;
sha1_init(&ctx) ;
sha1_update(&ctx, message, messagelen) ;
sha1_final(&ctx, digest) ;
</pre>
<ul>
<li> <tt>sha1_init()</tt> prepares a SHA1Schedule structure for computation </li>
<li> <tt>sha1_update()</tt> adds <em>message</em> to the message to be digested </li>
<li> <tt>sha1_final()</tt> computes the digest </li>
</ul>
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