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26 7u83 1 
#include "os.h"
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#include <mp.h>
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#include <libsec.h>
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mpint*
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dh_new(DHstate *dh, mpint *p, mpint *q, mpint *g)
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{
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	mpint *pm1;
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	int n;
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	memset(dh, 0, sizeof(*dh));
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	if(mpcmp(g, mpone) <= 0)
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		return nil;
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	n = mpsignif(p);
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	pm1 = mpnew(n);
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	mpsub(p, mpone, pm1);
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	dh->p = mpcopy(p);
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	dh->g = mpcopy(g);
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	dh->q = mpcopy(q != nil ? q : pm1);
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	dh->x = mpnew(mpsignif(dh->q));
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	dh->y = mpnew(n);
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	for(;;){
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		mpnrand(dh->q, genrandom, dh->x);
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		mpexp(dh->g, dh->x, dh->p, dh->y);
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		if(mpcmp(dh->y, mpone) > 0 && mpcmp(dh->y, pm1) < 0)
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			break;
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	}
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	mpfree(pm1);
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	return dh->y;
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}
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mpint*
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dh_finish(DHstate *dh, mpint *y)
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{
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	mpint *k = nil;
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	if(y == nil || dh->x == nil || dh->p == nil || dh->q == nil)
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		goto Out;
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	/* y > 1 */
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	if(mpcmp(y, mpone) <= 0)
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		goto Out;
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	k = mpnew(mpsignif(dh->p));
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	/* y < p-1 */
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	mpsub(dh->p, mpone, k);
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	if(mpcmp(y, k) >= 0){
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Bad:
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		mpfree(k);
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		k = nil;
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		goto Out;
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	}
56 
 
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	/* y**q % p == 1 if q < p-1 */
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	if(mpcmp(dh->q, k) < 0){
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		mpexp(y, dh->q, dh->p, k);
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		if(mpcmp(k, mpone) != 0)
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			goto Bad;
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	}
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	mpexp(y, dh->x, dh->p, k);
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Out:
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	mpfree(dh->p);
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	mpfree(dh->q);
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	mpfree(dh->g);
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	mpfree(dh->x);
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	mpfree(dh->y);
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	memset(dh, 0, sizeof(*dh));
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	return k;
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}