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<tr><td width=20><td><b>ELGAMAL(3)</b><td align=right><b>ELGAMAL(3)</b>
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<p><font size=+1><b>NAME </b></font><br>
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eggen, egencrypt, egdecrypt, egsign, egverify, egpuballoc, egpubfree,
egprivalloc, egprivfree, egsigalloc, egsigfree, egprivtopub -
elgamal encryption<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>EGpriv* &nbsp;&nbsp;&nbsp;&nbsp;eggen(int nlen, int nrep)
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<tt><font size=+1>mpint* &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;egencrypt(EGpub *k, mpint *in, mpint *out)
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<tt><font size=+1>mpint* &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;egdecrypt(EGpriv *k, mpint *in, mpint *out)
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<tt><font size=+1>EGsig* &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;egsign(EGpriv *k, mpint *m)
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<tt><font size=+1>int &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;egverify(EGpub *k, EGsig *sig, mpint *m)
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<tt><font size=+1>EGpub* &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;egpuballoc(void)
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<tt><font size=+1>void &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;egpubfree(EGpub*)
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<tt><font size=+1>EGpriv* &nbsp;&nbsp;&nbsp;&nbsp;egprivalloc(void)
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<tt><font size=+1>void &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;egprivfree(EGpriv*)
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<tt><font size=+1>EGsig* &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;egsigalloc(void)
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<tt><font size=+1>void &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;egsigfree(EGsig*)
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<tt><font size=+1>EGpub* &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;egprivtopub(EGpriv*)<br>
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<p><font size=+1><b>DESCRIPTION </b></font><br>
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Elgamal is a public key encryption and signature algorithm. The
owner of a key publishes the public part of the key:<br>
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<tt><font size=+1>struct EGpub<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;*alpha; &nbsp;&nbsp;&nbsp;&nbsp;// generator<br>
mpint &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;*key; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;// (encryption key) alpha**secret mod p<br>
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};<br>
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This part can be used for encrypting data (with <i>egencrypt</i>) to
be sent to the owner. The owner decrypts (with <i>egdecrypt</i>) using
his private key:<br>
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<tt><font size=+1>struct EGpriv<br>
{<br>
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EGpub &nbsp;&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>eggen</i>. <i>Eggen</i> takes both bit length of
the modulus and the number of repetitions of the Miller-Rabin
primality test to run. If the latter is 0, it does the default
number of rounds. <i>Egprivtopub</i> returns a newly allocated copy of
the public key corresponding to the private key.
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The routines <i>egpuballoc</i>, <i>egpubfree</i>, <i>egprivalloc</i>, and <i>egprivfree</i>
are provided to manage key storage.
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<i>Egsign</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 EGsig<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>Egverify</i> returns 0 if the signature is valid and &ndash;1 if not.
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The routines <i>egsigalloc</i> and <i>egsigfree</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/dsa.html"><i>dsa</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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