Re-arrange SM2

src/sm2_commit.c

@@ -0,0 +1,126 @@
+/*
+ *  Copyright 2014-2022 The GmSSL Project. All Rights Reserved.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the License); you may
+ *  not use this file except in compliance with the License.
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ */
+
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <limits.h>
+#include <stdint.h>
+#include <gmssl/sm2.h>
+#include <gmssl/sm3.h>
+#include <gmssl/asn1.h>
+#include <gmssl/error.h>
+
+
+#define SM2_H_TEXT "GmSSL SM2 Pederson Commitment Generator H"
+
+
+static int sm2_bn_rshift(SM2_BN ret, const SM2_BN a, unsigned int nbits)
+{
+	SM2_BN r;
+	int i;
+	for (i = 0; i < 7; i++) {
+		r[i] = a[i] >> nbits;
+		r[i] |= (a[i+1] << (32 - nbits)) & 0xffffffff;
+	}
+	r[i] = a[i] >> nbits;
+	sm2_bn_copy(ret, r);
+	return 1;
+}
+
+int sm2_point_from_hash(SM2_POINT *R, const uint8_t *data, size_t datalen)
+{
+	SM2_BN u;
+	SM2_Fp x;
+	SM2_Fp y;
+	SM2_Fp s;
+	SM2_Fp s_;
+	uint8_t dgst[32];
+
+	// u = (p-1)/4
+	sm2_bn_sub(u, SM2_P, SM2_ONE);
+	sm2_bn_rshift(u, u, 2);
+
+	do {
+		sm3_digest(data, datalen, dgst);
+
+		sm2_bn_from_bytes(x, dgst);
+		if (sm2_bn_cmp(x, SM2_P) >= 0) {
+			sm2_bn_sub(x, x, SM2_P);
+		}
+
+		// s = x^3 + a*x + b
+		sm2_fp_sqr(s, x);
+		sm2_fp_sub(s, s, SM2_THREE);
+		sm2_fp_mul(s, s, x);
+		sm2_fp_add(s, s, SM2_B);
+
+		// y = s^((p-1)/4) = (sqrt(s) (mod p))
+		sm2_fp_exp(y, s, u);
+		sm2_fp_sqr(s_, y);
+
+		data = dgst;
+		datalen = sizeof(dgst);
+
+	} while (sm2_bn_cmp(s, s_) != 0);
+
+	sm2_bn_to_bytes(x, R->x);
+	sm2_bn_to_bytes(y, R->y);
+	return 1;
+}
+
+int sm2_pederson_do_commit(const SM2_POINT *H, const uint8_t a[32], uint8_t r[32], SM2_POINT *C)
+{
+	SM2_BN r_;
+	SM2_BN a_;
+
+	sm2_bn_from_bytes(a_, a);
+	if (sm2_bn_cmp(a_, SM2_N) >= 0) {
+		error_print();
+		memset(a_, 0, sizeof(a_));
+		return -1;
+	}
+
+	do {
+		sm2_fn_rand(r_);
+	} while (sm2_bn_is_zero(r_));
+
+	sm2_bn_to_bytes(r_, r);
+
+	// C= r*H + a*G
+	sm2_point_mul_sum(C, r, H, a);
+
+	memset(a_, 0, sizeof(a_));
+	memset(r_, 0, sizeof(r_));
+	return 1;
+}
+
+int sm2_pederson_do_open(const SM2_POINT *H, const SM2_POINT *C, const uint8_t a[32], const uint8_t r[32])
+{
+	SM2_BN a_;
+	SM2_POINT C_;
+
+	sm2_bn_from_bytes(a_, a);
+	if (sm2_bn_cmp(a_, SM2_N) >= 0) {
+		error_print();
+		memset(a_, 0, sizeof(a_));
+		return -1;
+	}
+
+	sm2_point_mul_sum(&C_, r, H, a);
+	if (memcmp(&C, C, sizeof(SM2_POINT)) != 0) {
+		error_print();
+		memset(a_, 0, sizeof(a_));
+		return 0;
+	}
+
+	memset(a_, 0, sizeof(a_));
+	return 1;
+}
+