int main()
{
bigint_t a,b,c;
int buf[200];
bigint_new(&a,buf,50);
bigint_new(&b,buf+50,50);
bigint_new(&c,buf+100,100);
a2big(&a,"123456789123456789");
a2big(&b,"9876543210");
bigint_mult(&a,&b,&c);
printbig(&c);
printf("\n");
return 0;
}
/*
* RSA Sign using Garners algorithm and Chinese Remainder theorem.
* See the derivation on page 613 in handbook of applied cryptography
* use factors dp and dq of secret exponent d and p and q of public
* exponent n, and qinv
*/
void
CSL_ComputeRsaSigFast(u8 *result, u32 *message, u32 *certpublickey, u32 *certp, u32 *certq, u32 *dmp, u32 *dmq, u32 *qinv, int num_bits)
{
u32 pDigits, qDigits, cDigits, nDigits;
bigint_digit bigp[MAX_BIGINT_DIGITS];
bigint_digit bigq[MAX_BIGINT_DIGITS];
bigint_digit bigc[MAX_BIGINT_DIGITS];
bigint_digit bigdmp[MAX_BIGINT_DIGITS];
bigint_digit bigdmq[MAX_BIGINT_DIGITS];
bigint_digit bigqinv[MAX_BIGINT_DIGITS];
bigint_digit bign[MAX_BIGINT_DIGITS];
bigint_digit cP[MAX_BIGINT_DIGITS];
bigint_digit cQ[MAX_BIGINT_DIGITS];
bigint_digit mP[MAX_BIGINT_DIGITS];
bigint_digit mQ[MAX_BIGINT_DIGITS];
bigint_digit temp[MAX_BIGINT_DIGITS];
int outlen;
int i;
int num_words = num_bits/BIGINT_DIGIT_BITS;
bigint_zero(bigp, MAX_BIGINT_DIGITS);
bigint_zero(bigq, MAX_BIGINT_DIGITS);
bigint_zero(bigdmp, MAX_BIGINT_DIGITS);
bigint_zero(bigdmq, MAX_BIGINT_DIGITS);
bigint_zero(bigqinv, MAX_BIGINT_DIGITS);
bigint_zero(bigc, MAX_BIGINT_DIGITS);
for (i = 0; i < num_words/2; i++) {
bigp[num_words/2 - 1 - i] = certp[i];
bigq[num_words/2 - 1 - i] = certq[i];
bigdmp[num_words/2 - 1 - i] = dmp[i];
bigdmq[num_words/2 - 1 - i] = dmq[i];
bigqinv[num_words/2 - 1 - i] = qinv[i];
}
for (i = 0; i < num_words; i++) {
bigc[num_words - 1 - i] = message[i];
bign[num_words - 1 - i] = certpublickey[i];
}
cDigits = bigint_digits(bigc, MAX_BIGINT_DIGITS);
pDigits = bigint_digits(bigp, MAX_BIGINT_DIGITS);
qDigits = bigint_digits(bigq, MAX_BIGINT_DIGITS);
nDigits = bigint_digits(bign, MAX_BIGINT_DIGITS);
/*
* compute cP and cQ
*/
bigint_mod(cP, bigc, cDigits, bigp, pDigits);
bigint_mod(cQ, bigc, cDigits, bigq, qDigits);
/*
* Compute mP = cP^dP mod p and mQ = cQ^dQ mod q.
*/
bigint_mod_exp(mP, cP, bigdmp, pDigits, bigp, pDigits);
bigint_zero(mQ, nDigits);
bigint_mod_exp(mQ, cQ, bigdmq, pDigits, bigq, pDigits);
/*
* do CRT
* m = ((((mP - mQ) mod p)*qinv) mod p) *q + mQ
*/
if (bigint_cmp(mP, mQ, pDigits) >= 0) {
bigint_sub(temp, mP, mQ, pDigits);
} else {
bigint_sub(temp, mQ, mP, pDigits);
bigint_sub(temp, bigp, temp, pDigits);
}
bigint_mod_mult(temp, temp, bigqinv, bigp, pDigits);
bigint_mult(temp, temp, bigq, pDigits);
bigint_add(temp, temp, mQ, nDigits);
outlen = (num_bits + 7)/8;
I2OSP(result, outlen, temp, nDigits);
}
