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implemented the coefficient shift into a range of -q/2 and q/2

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This commit is contained in:
Christoph Prüßner 2014-05-03 14:57:05 +02:00
parent b4a7870e97
commit fa97531eac
2 changed files with 22 additions and 7 deletions
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24
src/ntru_decrypt.c
View File

@ -38,22 +38,34 @@
// Require: N , q, p, secret key f , inverse polynomial Fp , and encrypted message e.
int ntru_decrypt(pb_poly *encr_msg, pb_poly *private_key, ntru_context *context, char ** decr_msg){
// toDo q = ?, p = ?, fp = ?
// toDo fp = ?
unsigned int q = context->q;
unsigned int p = context->p;
unsigned int N = context->N;
// StarMultiply(f, e, a, N, q)
pb_poly *a;
pb_poly *a = build_polynom(NULL, N, context);
pb_starmultiply(private_key, encr_msg, a, context, q);
mp_int mp_q;
mp_int mp_qdiv2;
mp_int zero;
init_integer(&mp_q);
init_integer(&mp_qdiv2);
init_integer(&zero);
MP_SET_INT(&mp_q, q);
mp_div_2(&mp_q, mp_qdiv2);
mp_zero(&zero);
for(int i = 0, i < N, i++){
if(a[i] < 0 ) {
a[i] = a[i] + q; // Make all coefficients positive
if(mp_cmp(&(a->terms[i]),&zero) == MP_LT) { // Make all coefficients positive
a->terms[i] = a->terms[i] + q;
}
if(a[i] > q/2) {
a[i] = a[i] - q // Shift coefficients of a into range (−q/2, q/2)
if(mp_cmp(&(a->terms[i]), &mp_qdiv2) == MP_GT) { // Shift coefficients of a into range (−q/2, q/2)
a->terms[i] = a->terms[i] - mp_q;
}
}
//toDo StarMultiply(a, Fp , d, N, p)

5
src/ntru_decrypt.h
View File

@ -25,6 +25,9 @@
#include "poly.h"
#include "context.h"
int ntru_decrypt(pb_poly *encr_msg, pb_poly *private_key, ntru_context *context, char ** decr_msg);
int ntru_decrypt(pb_poly *encr_msg,
pb_poly *private_key,
ntru_context *context,
char ** decr_msg);
#endif /* NTRU_DECRYPT */