44 lines
807 B
C
44 lines
807 B
C
#include "os.h"
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#include <mp.h>
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#include <libsec.h>
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EGsig*
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egsign(EGpriv *priv, mpint *m)
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{
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EGpub *pub = &priv->pub;
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EGsig *sig;
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mpint *pm1, *k, *kinv, *r, *s;
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mpint *p = pub->p, *alpha = pub->alpha;
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int plen = mpsignif(p);
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pm1 = mpnew(0);
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kinv = mpnew(0);
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r = mpnew(0);
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s = mpnew(0);
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k = mpnew(0);
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mpsub(p, mpone, pm1);
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while(1){
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mprand(plen, genrandom, k);
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if((mpcmp(mpone, k) > 0) || (mpcmp(k, pm1) >= 0))
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continue;
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mpextendedgcd(k, pm1, r, kinv, s);
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if(mpcmp(r, mpone) != 0)
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continue;
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break;
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}
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mpmod(kinv, pm1, kinv); // make kinv positive
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mpexp(alpha, k, p, r);
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mpmul(priv->secret, r, s);
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mpmod(s, pm1, s);
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mpsub(m, s, s);
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mpmul(kinv, s, s);
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mpmod(s, pm1, s);
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sig = egsigalloc();
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sig->r = r;
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sig->s = s;
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mpfree(pm1);
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mpfree(k);
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mpfree(kinv);
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return sig;
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}
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