doc/libstdcrypto/index.html


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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> sha1 </li>
  <li> sha256 </li>
  <li> sha512 </li>
  <li> blake2s </li>
  <li> crc32c </li>
</ul>

<p>
 Please bear in mind that sha1 is practically broken.
Do not use it in security-critical applications.
</p>

<h2> Compiling </h2>

<ul>
 <li> Use <tt>#include &lt;skalibs/stdcrypto.h&gt;</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="sha1"></a>
SHA1 </h3>

<pre>
  SHA1Schedule ctx ;
  char const *message ;
  size_t messagelen ;
  unsigned char digest[20] ;

  sha1_init(&amp;ctx) ;
  sha1_update(&amp;ctx, message, messagelen) ;
  sha1_final(&amp;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>

<h3> <a name="sha256"></a>
SHA256 </h3>

<pre>
  SHA256Schedule ctx ;
  char const *message ;
  size_t messagelen ;
  char digest[32] ;

  sha256_init(&amp;ctx) ;
  sha256_update(&amp;ctx, message, messagelen) ;
  sha256_final(&amp;ctx, digest) ;
</pre>

<ul>
  <li> <tt>sha256_init()</tt> prepares a SHA256Schedule structure for computation </li>
  <li> <tt>sha256_update()</tt> adds <em>message</em> to the message to be digested </li>
  <li> <tt>sha256_final()</tt> computes the digest </li>
</ul>

<h3> <a name="sha512"></a>
SHA512 </h3>

<pre>
  SHA512Schedule ctx ;
  char const *message ;
  size_t messagelen ;
  char digest[64] ;

  sha512_init(&amp;ctx) ;
  sha512_update(&amp;ctx, message, messagelen) ;
  sha512_final(&amp;ctx, digest) ;
</pre>

<ul>
  <li> <tt>sha512_init()</tt> prepares a SHA512Schedule structure for computation </li>
  <li> <tt>sha512_update()</tt> adds <em>message</em> to the message to be digested </li>
  <li> <tt>sha512_final()</tt> computes the digest </li>
</ul>

<h3> <a name="blake2s"></a>
blake2s </h3>

 Same scheme as with the other hashes.

<pre>
  blake2s_ctx ctx ;
  char const *message ;
  size_t messagelen ;
  size_t outlen = 32 ;  /* the user gives the length of the digest */
  char digest[outlen] ;

  blake2s_init(&amp;ctx, outlen) ;
  blake2s_update(&amp;ctx, message, messagelen) ;
  blake2s_final(&amp;ctx, digest) ;
</pre>

<h3> <a name="crc32c"></a>
crc32c </h3>

 This isn't a cryptography primitive, but just a function to compute
the Castagnoli version of a cyclic redundancy code.

<pre>
  uint32_t crc = 0 ;  /* no need for context except that crc needs to be initialized to 0 */
  char const *message ;
  size_t messagelen ;

  crc = crc32c(crc, message, messagelen) ;
</pre>

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