POLY: first try of implementing pb_inverse_poly_p()
This ends up as an infinite loop though.
This commit is contained in:
parent
777a086c53
commit
4d5f44c900
146
src/poly.c
146
src/poly.c
|
|
@ -409,6 +409,152 @@ OUT_OF_LOOP:
|
|||
|
||||
return true;
|
||||
}
|
||||
|
||||
/**
|
||||
* Invert the polynomial a modulo p.
|
||||
*
|
||||
* @param a polynomial to invert
|
||||
* @param Fq polynomial [out]
|
||||
* @param ctx NTRU context
|
||||
*/
|
||||
bool pb_inverse_poly_p(pb_poly *a,
|
||||
pb_poly *Fp,
|
||||
ntru_context *ctx)
|
||||
{
|
||||
int k = 0,
|
||||
j = 0;
|
||||
pb_poly *a_tmp, *b, *c, *f, *g;
|
||||
mp_int mp_modulus, mp_minus;
|
||||
|
||||
/* general initialization of temp variables */
|
||||
init_integer(&mp_modulus);
|
||||
init_integer(&mp_minus);
|
||||
MP_SET_INT(&mp_modulus, (unsigned long)(ctx->p));
|
||||
MP_SET_INT(&mp_minus, 1);
|
||||
mp_neg(&mp_minus, &mp_minus);
|
||||
b = build_polynom(NULL, ctx->N + 1, ctx);
|
||||
MP_SET(&(b->terms[0]), 1);
|
||||
c = build_polynom(NULL, ctx->N + 1, ctx);
|
||||
f = build_polynom(NULL, ctx->N + 1, ctx);
|
||||
PB_COPY(a, f);
|
||||
|
||||
/* set g(x) = x^N − 1 */
|
||||
g = build_polynom(NULL, ctx->N + 1, ctx);
|
||||
MP_SET(&(g->terms[0]), 1);
|
||||
mp_neg(&(g->terms[0]), &(g->terms[0]));
|
||||
MP_SET(&(g->terms[ctx->N]), 1);
|
||||
|
||||
/* avoid side effects */
|
||||
a_tmp = build_polynom(NULL, ctx->N, ctx);
|
||||
PB_COPY(a, a_tmp);
|
||||
erase_polynom(Fp, ctx->N);
|
||||
|
||||
printf("f: "); draw_polynom(f);
|
||||
printf("g: "); draw_polynom(g);
|
||||
|
||||
while (1) {
|
||||
while (mp_cmp_d(&(f->terms[0]), 0) == MP_EQ) {
|
||||
printf("blah\n");
|
||||
for (unsigned int i = 1; i <= ctx->N; i++) {
|
||||
/* f(x) = f(x) / x */
|
||||
MP_COPY(&(f->terms[i]), &(f->terms[i - 1]));
|
||||
/* c(x) = c(x) * x */
|
||||
MP_COPY(&(c->terms[ctx->N - i]), &(c->terms[ctx->N + 1 - i]));
|
||||
}
|
||||
MP_SET(&(f->terms[ctx->N]), 0);
|
||||
MP_SET(&(c->terms[0]), 0);
|
||||
k++;
|
||||
}
|
||||
|
||||
if (get_degree(f) == 0)
|
||||
goto OUT_OF_LOOP2;
|
||||
|
||||
if (get_degree(f) < get_degree(g)) {
|
||||
pb_exch(f, g);
|
||||
pb_exch(b, c);
|
||||
}
|
||||
|
||||
{
|
||||
pb_poly *u, *c_tmp, *g_tmp;
|
||||
mp_int mp_tmp;
|
||||
|
||||
init_integer(&mp_tmp);
|
||||
u = build_polynom(NULL, ctx->N, ctx);
|
||||
g_tmp = build_polynom(NULL, ctx->N + 1, ctx);
|
||||
PB_COPY(g, g_tmp);
|
||||
c_tmp = build_polynom(NULL, ctx->N + 1, ctx);
|
||||
PB_COPY(c, c_tmp);
|
||||
|
||||
/* u = ((f[0] mod p) * (g[0] inverse mod p) mod p) */
|
||||
printf("u before: "); draw_polynom(u);
|
||||
MP_COPY(&(f->terms[0]), &mp_tmp); /* don't change f[0] */
|
||||
MP_INVMOD(&(g->terms[0]), &mp_modulus, &(u->terms[0]));
|
||||
MP_MOD(&mp_tmp, &mp_modulus, &mp_tmp);
|
||||
MP_MUL(&(u->terms[0]), &mp_tmp, &(u->terms[0]));
|
||||
MP_MOD(&(u->terms[0]), &mp_modulus, &(u->terms[0]));
|
||||
|
||||
/* f = f - u * g mod p */
|
||||
printf("f before: "); draw_polynom(f);
|
||||
PB_MUL(g_tmp, u, g_tmp);
|
||||
PB_SUB(f, g_tmp, f);
|
||||
PB_MOD(f, &mp_modulus, f, ctx->N + 1);
|
||||
|
||||
/* b = b - u * c mod p */
|
||||
printf("b before: "); draw_polynom(b);
|
||||
PB_MUL(c_tmp, u, c_tmp);
|
||||
PB_SUB(b, c_tmp, b);
|
||||
PB_MOD(b, &mp_modulus, b, ctx->N + 1);
|
||||
printf("u after: "); draw_polynom(u);
|
||||
printf("f after: "); draw_polynom(f);
|
||||
printf("g after: "); draw_polynom(g);
|
||||
printf("b after: "); draw_polynom(b);
|
||||
|
||||
mp_clear(&mp_tmp);
|
||||
delete_polynom_multi(u, c_tmp, g_tmp, NULL);
|
||||
}
|
||||
}
|
||||
|
||||
OUT_OF_LOOP2:
|
||||
k = k % ctx->N;
|
||||
|
||||
/* Fp(x) = x^(N-k) * b(x) */
|
||||
for (int i = ctx->N - 1; i >= 0; i--) {
|
||||
|
||||
/* b(X) = f[0]^(-1) * b(X) (mod p) */
|
||||
{
|
||||
pb_poly *poly_tmp;
|
||||
|
||||
poly_tmp = build_polynom(NULL, ctx->N + 1, ctx);
|
||||
|
||||
MP_INVMOD(&(f->terms[0]), &mp_modulus, &(poly_tmp->terms[0]));
|
||||
MP_MOD(&(b->terms[i]), &mp_modulus, &(b->terms[i]));
|
||||
MP_MUL(&(b->terms[i]), &(poly_tmp->terms[0]), &(b->terms[i]));
|
||||
|
||||
delete_polynom(poly_tmp);
|
||||
}
|
||||
|
||||
j = i - k;
|
||||
if (j < 0)
|
||||
j = j + ctx->N;
|
||||
MP_COPY(&(b->terms[i]), &(Fp->terms[j]));
|
||||
|
||||
/* delete_polynom(f_tmp); */
|
||||
}
|
||||
|
||||
/* pull into positive space */
|
||||
for (int i = ctx->N - 1; i >= 0; i--)
|
||||
if (mp_cmp_d(&(Fp->terms[i]), 0) == MP_LT)
|
||||
MP_ADD(&(Fp->terms[i]), &mp_modulus, &(Fp->terms[i]));
|
||||
|
||||
mp_clear(&mp_modulus);
|
||||
delete_polynom_multi(a_tmp, b, c, f, g, NULL);
|
||||
|
||||
/* TODO: check if the f * Fq = 1 (mod p) condition holds true */
|
||||
|
||||
return true;
|
||||
}
|
||||
|
||||
/**
|
||||
* Print the polynomial in a human readable format to stdout.
|
||||
*
|
||||
* @param poly to draw
|
||||
|
|
|
|||
12
src/poly.h
12
src/poly.h
|
|
@ -105,6 +105,14 @@
|
|||
mp_error_to_string(result)); \
|
||||
}
|
||||
|
||||
#define MP_INVMOD(...) \
|
||||
{ \
|
||||
int result; \
|
||||
if ((result = mp_invmod(__VA_ARGS__)) != MP_OKAY) \
|
||||
NTRU_ABORT("Error computing modular inverse. %s", \
|
||||
mp_error_to_string(result)); \
|
||||
}
|
||||
|
||||
#define MP_EXPT_D(...) \
|
||||
{ \
|
||||
int result; \
|
||||
|
|
@ -182,6 +190,10 @@ bool pb_inverse_poly_q(pb_poly *a,
|
|||
pb_poly *Fq,
|
||||
ntru_context *ctx);
|
||||
|
||||
bool pb_inverse_poly_p(pb_poly *a,
|
||||
pb_poly *Fp,
|
||||
ntru_context *ctx);
|
||||
|
||||
void draw_polynom(pb_poly * const poly);
|
||||
|
||||
#endif /* NTRU_POLY_H */
|
||||
|
|
|
|||
Loading…
Reference in New Issue