IV CLASS="lisp-symbol"><A NAME="block-length"></A><TT><STRONG>block-length</STRONG> <EM>cipher</EM> =&gt; <EM>number</EM></TT><BR /></DIV><P>Return the number of octets <EM>cipher</EM> processes at a time.  This
function always returns 1 for stream ciphers.</P><H2 ID="digests">Digests</H2><P>Digest functions, also known as hash functions, produce
fixed-length output (a <EM>digest</EM> or <EM>hash</EM>) from a
variable-length message.  The simplest example of a digest function is
one that adds up all the byt