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<tr><td width=20><td><b>DSA(3)</b><td align=right><b>DSA(3)</b>
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<p><font size=+1><b>NAME </b></font><br>
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dsagen, dsasign, dsaverify, dsapuballoc, dsapubfree, dsaprivalloc,
dsaprivfree, dsasigalloc, dsasigfree, dsaprivtopub - digital signature
algorithm<br>
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<p><font size=+1><b>SYNOPSIS </b></font><br>
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<tt><font size=+1>#include &lt;u.h&gt;<br>
#include &lt;libc.h&gt;<br>
#include &lt;mp.h&gt;<br>
#include &lt;libsec.h&gt;
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<tt><font size=+1>DSApriv* &nbsp;&nbsp;&nbsp;dsagen(DSApub *opub)
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<tt><font size=+1>DSAsig* &nbsp;&nbsp;&nbsp;&nbsp;dsasign(DSApriv *k, mpint *m)
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<tt><font size=+1>int &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;dsaverify(DSApub *k, DSAsig *sig, mpint *m)
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<tt><font size=+1>DSApub* &nbsp;&nbsp;&nbsp;&nbsp;dsapuballoc(void)
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<tt><font size=+1>void &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;dsapubfree(DSApub*)
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<tt><font size=+1>DSApriv* &nbsp;&nbsp;&nbsp;dsaprivalloc(void)
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<tt><font size=+1>void &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;dsaprivfree(DSApriv*)
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<tt><font size=+1>DSAsig* &nbsp;&nbsp;&nbsp;&nbsp;dsasigalloc(void)
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<tt><font size=+1>void &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;dsasigfree(DSAsig*)
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<tt><font size=+1>DSApub* &nbsp;&nbsp;&nbsp;&nbsp;dsaprivtopub(DSApriv*)<br>
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<p><font size=+1><b>DESCRIPTION </b></font><br>
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DSA is the NIST approved digital signature algorithm. The owner
of a key publishes the public part of the key:<br>
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<tt><font size=+1>struct DSApub<br>
{<br>
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mpint &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;*p; &nbsp;&nbsp;&nbsp;// modulus<br>
mpint &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;*q; &nbsp;&nbsp;&nbsp;// group order, q divides p&#8722;1<br>
mpint &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;*alpha; &nbsp;&nbsp;&nbsp;&nbsp;// group generator<br>
mpint &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;*key; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;// alpha**secret mod p<br>
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};<br>
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This part can be used for verifying signatures (with <i>dsaverify</i>)
created by the owner. The owner signs (with <i>dsasign</i>) using his
private key:<br>
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<tt><font size=+1>struct DSApriv<br>
{<br>
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DSApub &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;pub;<br>
mpint &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;*secret; // (decryption key)<br>
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};<br>
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Keys are generated using <i>dsagen</i>. If <i>dsagen</i>&#8217;s argument <i>opub</i> is
<tt><font size=+1>nil</font></tt>, a key is created using a new <tt><font size=+1>p</font></tt> and <tt><font size=+1>q</font></tt> generated by <i>DSAprimes</i>
(see <a href="../man3/prime.html"><i>prime</i>(3)</a>). Otherwise, <tt><font size=+1>p</font></tt> and <tt><font size=+1>q</font></tt> are copied from the old key.
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<i>Dsaprivtopub</i> returns a newly allocated copy of the public key
corresponding to the private key.
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The routines <i>dsapuballoc</i>, <i>dsapubfree</i>, <i>dsaprivalloc</i>, and <i>dsaprivfree</i>
are provided to manage key storage.
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<i>Dsasign</i> signs message <i>m</i> using a private key <i>k</i> yielding a<br>
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<tt><font size=+1>struct DSAsig<br>
{<br>
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mpint &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;*r, *s;<br>
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};<br>
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<i>Dsaverify</i> returns 0 if the signature is valid and &ndash;1 if not.
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The routines <i>dsasigalloc</i> and <i>dsasigfree</i> are provided to manage
signature storage.<br>
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<p><font size=+1><b>SOURCE </b></font><br>
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<tt><font size=+1>/usr/local/plan9/src/libsec<br>
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<p><font size=+1><b>SEE ALSO </b></font><br>
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<a href="../man3/mp.html"><i>mp</i>(3)</a>, <a href="../man3/aes.html"><i>aes</i>(3)</a>, <a href="../man3/blowfish.html"><i>blowfish</i>(3)</a>, <a href="../man3/des.html"><i>des</i>(3)</a>, <a href="../man3/rc4.html"><i>rc4</i>(3)</a>, <a href="../man3/rsa.html"><i>rsa</i>(3)</a>, <a href="../man3/sechash.html"><i>sechash</i>(3)</a>,
<a href="../man3/prime.html"><i>prime</i>(3)</a>, <a href="../man3/rand.html"><i>rand</i>(3)</a><br>
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