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// -*-c++-*-
/* $Id: esign.h,v 1.4 2004/09/20 00:31:49 dm Exp $ */
/*
*
* Copyright (C) 1998 David Mazieres (dm@uun.org)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2, or (at
* your option) any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
* USA
*
*/
#include "bigint.h"
#include "modalg.h"
class esign_pub {
public:
const bigint n;
const u_long k;
const int log2k; // log_2 (k), or -1 if k not power of 2
protected:
bigint t;
static void msg2bigint (bigint *resp, const str &msg, int bits);
static int calc_log2k (u_long k);
public:
void kpow (bigint *rp, const bigint &x) const {
#if 1
*rp = powm (x, k, n);
#else /* This seems to be slower on the P4 */
if (log2k <= 0)
*rp = powm (x, k, n);
else {
bigint tmp;
mpz_square (&tmp, &x);
mpz_mod (rp, &tmp, &n);
for (int i = log2k - 1; i > 0; i--) {
mpz_square (&tmp, rp);
mpz_mod (rp, &tmp, &n);
}
}
#endif
}
esign_pub (const bigint &n, u_long k);
bool raw_verify (const bigint &msg, const bigint &sig) const;
bool verify (const str &msg, const bigint &sig) const {
bigint z;
msg2bigint (&z, msg, mpz_sizeinbase2 (&n));
return raw_verify (z, sig);
}
};
class esign_priv : public esign_pub {
public:
bigint p;
bigint q;
protected:
bigint pq;
struct precomp {
bigint x;
bigint xk;
bigint x_over_kxk;
};
mutable vec<precomp, 2> prevec;
public:
esign_priv (const bigint &p, const bigint &q, u_long k);
void precompute () const;
size_t nprecomputed () const { return prevec.size (); }
bigint raw_sign (const bigint &m) const;
bigint sign (const str &msg) const {
bigint z;
msg2bigint (&z, msg, mpz_sizeinbase2 (&n));
return raw_sign (z);
}
};
esign_priv esign_keygen (size_t nbits, u_long k = 8);
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