37 lines
767 B
C
37 lines
767 B
C
#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 */
|
|
mpint*
|
|
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);
|
|
|
|
mpfree(v1);
|
|
mpfree(v2);
|
|
|
|
return out;
|
|
}
|