blob: 82e2eeea0e72a2d997e1d59e56acae7899f72ae9 [file] [log] [blame]
#include "os.h"
#include <mp.h>
#include <libsec.h>
/* decrypt rsa using garner's algorithm for the chinese remainder theorem */
/* seminumerical algorithms, knuth, pp 253-254 */
/* applied cryptography, menezes et al, pg 612 */
rsadecrypt(RSApriv *rsa, mpint *in, mpint *out)
mpint *v1, *v2;
if(out == nil)
out = mpnew(0);
/* convert in to modular representation */
v1 = mpnew(0);
mpmod(in, rsa->p, v1);
v2 = mpnew(0);
mpmod(in, rsa->q, v2);
/* exponentiate the modular rep */
mpexp(v1, rsa->kp, rsa->p, v1);
mpexp(v2, rsa->kq, rsa->q, v2);
/* out = v1 + p*((v2-v1)*c2 mod q) */
mpsub(v2, v1, v2);
mpmul(v2, rsa->c2, v2);
mpmod(v2, rsa->q, v2);
mpmul(v2, rsa->p, out);
mpadd(v1, out, out);
return out;