diff options
author | wukong <rebirthmonkey@gmail.com> | 2015-11-23 17:48:48 +0100 |
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committer | wukong <rebirthmonkey@gmail.com> | 2015-11-23 17:48:48 +0100 |
commit | fca74d4bc3569506a6659880a89aa009dc11f552 (patch) | |
tree | 4cefd06af989608ea8ebd3bc6306889e2a1ad175 /moon-abe/pbc-0.5.14/guru/19.c | |
parent | 840ac3ebca7af381132bf7e93c1e4c0430d6b16a (diff) |
moon-abe cleanup
Change-Id: Ie1259856db03f0b9e80de3e967ec6bd1f03191b3
Diffstat (limited to 'moon-abe/pbc-0.5.14/guru/19.c')
-rw-r--r-- | moon-abe/pbc-0.5.14/guru/19.c | 373 |
1 files changed, 0 insertions, 373 deletions
diff --git a/moon-abe/pbc-0.5.14/guru/19.c b/moon-abe/pbc-0.5.14/guru/19.c deleted file mode 100644 index 5e225565..00000000 --- a/moon-abe/pbc-0.5.14/guru/19.c +++ /dev/null @@ -1,373 +0,0 @@ -/* - * Toy example of a field where the Tate pairing can be used - * but the Weil pairing cannot. - * - * Consider the curve E: y^2 = x^3 + x + 6 over F_19: - * E(F_19) is a cyclic group of order 18. - * Thus E[3] is not contained in F_19 - * (it turns out E[3] is contained in F_19^3). - * - * Hence the Weil pairing cannot be defined over F_19 - * However, F_19 contains the cube roots of unity - * so we can compute the Tate pairing - */ - -/* - * P = (12,13) generates a group of order 3: - * <(12,13)> = {(12,13), (12,6), O} - * e(P,P) = 7, so we have the isomorphism - * <(12,13)> = <7> (in F_19^*) - * - * Similarly P = (4, 6) generates a group of order 9, and we find - * <(4,6)> = <4> - * - * P = (0, 5) generates all of E(F_19) - * Miller's algorithm will not allow us to calculate e(P, P) without - * first extending F_19. - * Instead of extending, we could manipulate rational functions since - * 19 is small enough that an explicit expression of f_P can be found. - */ - -#include "pbc.h" -#include "pbc_fp.h" -#include "pbc_fieldquadratic.h" - -static void miller(element_t res, element_t P, element_ptr QR, element_ptr R, int n) { - // Collate divisions. - int m; - element_t v, vd; - element_t Z; - element_t a, b, c; - const element_ptr cca = curve_a_coeff(P); - const element_ptr Px = curve_x_coord(P); - const element_ptr Py = curve_y_coord(P); - element_t e0, e1; - mpz_t q; - element_ptr Zx, Zy; - const element_ptr numx = curve_x_coord(QR); - const element_ptr numy = curve_y_coord(QR); - const element_ptr denomx = curve_x_coord(R); - const element_ptr denomy = curve_y_coord(R); - - void do_vertical(element_t e, element_t edenom) - { - element_sub(e0, numx, Zx); - element_mul(e, e, e0); - - element_sub(e0, denomx, Zx); - element_mul(edenom, edenom, e0); - } - - void do_tangent(element_t e, element_t edenom) - { - //a = -slope_tangent(A.x, A.y); - //b = 1; - //c = -(A.y + a * A.x); - //but we multiply by 2*A.y to avoid division - - //a = -Ax * (Ax + Ax + Ax + twicea_2) - a_4; - //Common curves: a2 = 0 (and cc->a is a_4), so - //a = -(3 Ax^2 + cc->a) - //b = 2 * Ay - //c = -(2 Ay^2 + a Ax); - - if (element_is0(Zy)) { - do_vertical(e, edenom); - return; - } - element_square(a, Zx); - element_mul_si(a, a, 3); - element_add(a, a, cca); - element_neg(a, a); - - element_add(b, Zy, Zy); - - element_mul(e0, b, Zy); - element_mul(c, a, Zx); - element_add(c, c, e0); - element_neg(c, c); - - element_mul(e0, a, numx); - element_mul(e1, b, numy); - element_add(e0, e0, e1); - element_add(e0, e0, c); - element_mul(e, e, e0); - - element_mul(e0, a, denomx); - element_mul(e1, b, denomy); - element_add(e0, e0, e1); - element_add(e0, e0, c); - element_mul(edenom, edenom, e0); - } - - void do_line(element_ptr e, element_ptr edenom) - { - if (!element_cmp(Zx, Px)) { - if (!element_cmp(Zy, Py)) { - do_tangent(e, edenom); - } else { - do_vertical(e, edenom); - } - return; - } - - element_sub(b, Px, Zx); - element_sub(a, Zy, Py); - element_mul(c, Zx, Py); - element_mul(e0, Zy, Px); - element_sub(c, c, e0); - - element_mul(e0, a, numx); - element_mul(e1, b, numy); - element_add(e0, e0, e1); - element_add(e0, e0, c); - element_mul(e, e, e0); - - element_mul(e0, a, denomx); - element_mul(e1, b, denomy); - element_add(e0, e0, e1); - element_add(e0, e0, c); - element_mul(edenom, edenom, e0); - } - - element_init(a, res->field); - element_init(b, res->field); - element_init(c, res->field); - element_init(e0, res->field); - element_init(e1, res->field); - - element_init(v, res->field); - element_init(vd, res->field); - element_init(Z, P->field); - - element_set(Z, P); - Zx = curve_x_coord(Z); - Zy = curve_y_coord(Z); - - element_set1(v); - element_set1(vd); - - mpz_init(q); - mpz_set_ui(q, n); - m = mpz_sizeinbase(q, 2) - 2; - - while(m >= 0) { - element_square(v, v); - element_square(vd, vd); - do_tangent(v, vd); - element_double(Z, Z); - do_vertical(vd, v); - - if (mpz_tstbit(q, m)) { - do_line(v, vd); - element_add(Z, Z, P); - if (m) { - do_vertical(vd, v); - } - } - m--; - } - - mpz_clear(q); - - element_invert(vd, vd); - element_mul(res, v, vd); - - element_clear(v); - element_clear(vd); - element_clear(Z); - element_clear(a); - element_clear(b); - element_clear(c); - element_clear(e0); - element_clear(e1); -} - -static void tate_3(element_ptr out, element_ptr P, element_ptr Q, element_ptr R) { - mpz_t six; - - mpz_init(six); - mpz_set_ui(six, 6); - element_t QR; - element_t e0; - - element_init(QR, P->field); - element_init(e0, out->field); - - element_add(QR, Q, R); - - //for subgroup size 3, -2P = P, hence - //the tangent line at P has divisor 3(P) - 3(O) - - miller(out, P, QR, R, 3); - - element_pow_mpz(out, out, six); - element_clear(QR); - element_clear(e0); - mpz_clear(six); -} - -static void tate_9(element_ptr out, element_ptr P, element_ptr Q, element_ptr R) { - element_t QR; - element_init(QR, P->field); - - element_add(QR, Q, R); - - miller(out, P, QR, R, 9); - - element_square(out, out); - - element_clear(QR); -} - -static void tate_18(element_ptr out, element_ptr P, element_ptr Q, element_ptr R, element_ptr S) { - mpz_t pow; - element_t PR; - element_t QS; - element_init(PR, P->field); - element_init(QS, P->field); - element_t outd; - - element_init(outd, out->field); - - mpz_init(pow); - mpz_set_ui(pow, (19*19-1)/18); - - element_add(PR, P, R); - element_add(QS, Q, S); - - if (element_is0(QS)) { - element_t S2; - element_init(S2, P->field); - element_double(S2, S); - miller(out, PR, S, S2, 18); - miller(outd, R, S, S2, 18); - element_clear(S2); - } else { - miller(out, PR, QS, S, 18); - miller(outd, R, QS, S, 18); - } - - element_clear(PR); - element_clear(QS); - - element_invert(outd, outd); - element_mul(out, out, outd); - element_pow_mpz(out, out, pow); - - element_clear(outd); - mpz_clear(pow); -} - -int main(void) { - field_t c; - field_t Z19; - element_t P, Q, R; - mpz_t q, z; - element_t a, b; - int i; - - field_t Z19_2; - field_t c2; - element_t P2, Q2, R2; - element_t a2; - - mpz_init(q); - mpz_init(z); - - mpz_set_ui(q, 19); - - field_init_fp(Z19, q); - element_init(a, Z19); - element_init(b, Z19); - - element_set_si(a, 1); - element_set_si(b, 6); - - mpz_set_ui(q, 18); - field_init_curve_ab(c, a, b, q, NULL); - element_init(P, c); - element_init(Q, c); - element_init(R, c); - - printf("Y^2 = X^3 + X + 6 over F_19\n"); - //(0,+/-5) is a generator - element_set0(a); - curve_from_x(R, a); - - for (i=1; i<19; i++) { - mpz_set_si(z, i); - element_mul_mpz(Q, R, z); - element_printf("%dR = %B\n", i, Q); - } - - mpz_set_ui(z, 6); - element_mul_mpz(P, R, z); - //P has order 3 - element_printf("P = %B\n", P); - - for (i=1; i<=3; i++) { - mpz_set_si(z, i); - element_mul_mpz(Q, R, z); - tate_3(a, P, Q, R); - element_printf("e_3(P,%dR) = %B\n", i, a); - } - - element_double(P, R); - //P has order 9 - element_printf("P = %B\n", P); - for (i=1; i<=9; i++) { - mpz_set_si(z, i); - //we're supposed to use multiples of R - //but 2R works just as well and it allows us - //to use R as the offset every time - element_mul_mpz(Q, P, z); - tate_9(a, P, Q, R); - element_printf("e_9(P,%dP) = %B\n", i, a); - } - - //to do the pairing on all of E(F_19) we need to move to F_19^2 - //or compute the rational function explicitly - printf("moving to F_19^2\n"); - field_init_fi(Z19_2, Z19); - - //don't need to tell it the real order - field_init_curve_ab_map(c2, c, element_field_to_fi, Z19_2, q, NULL); - element_init(P2, c2); - element_init(Q2, c2); - element_init(R2, c2); - - element_init(a2, Z19_2); - element_set0(a2); - curve_from_x(P2, a2); - - element_random(R2); - - element_printf("P = %B\n", P2); - - for (i=1; i<=18; i++) { - mpz_set_si(z, i); - element_mul_mpz(Q2, P2, z); - tate_18(a2, P2, Q2, R2, P2); - element_printf("e_18(P,%dP) = %B\n", i, a2); - } - - element_clear(P2); - element_clear(Q2); - element_clear(R2); - element_clear(a2); - field_clear(c2); - field_clear(Z19_2); - - field_clear(c); - element_clear(a); - element_clear(b); - element_clear(P); - element_clear(Q); - element_clear(R); - field_clear(Z19); - - mpz_clear(q); - mpz_clear(z); - return 0; -} |