 (
<pre>
    char*   d1,   /* data to be truncated */
    char*   d2,   /* truncated data */
    int     len   /* length in bytes to keep */
   )
   {
           int     i ;
           for (i = 0 ; i &lt; len ; i++) d2[i] = d1[i];
   }
</pre>
<p>
<dt><hr><dd>
<dt><em><a name="page-8">Page 8</a></em><dd><p>
<pre>
   /* Function to compute the digest */
   void
   hmac_sha
   (
    char*    k,     /* secret key */
    int      lk,    /* length of the key in bytes */
    char*    d,     /* data */
    int     