ref: b540a22eb0c287398e21358d6b66c8e544001f77
dir: /sys/src/libsec/port/rsadecrypt.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; }