packages; <TT>:STREAM</TT>, <TT>IRONCLAD:OFB</TT>, and so forth.  An error
will be signaled if <EM>mode</EM> is not appropriate for the cipher <EM>name</EM>.</P><P><EM>initialization-vector</EM> (IV) should be supplied only if <EM>mode</EM>
requires one.  <EM>initialization-vector</EM> should be a <TT>(VECTOR
(UNSIGNED-BYTE 8))</TT>.  The supplied IV should be the same length as the
<A HREF="#block-length" STYLE="symbol">block-length</A> of <EM>name</EM>.</P><P><EM>key</EM> is, of course, the key for the ci