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ecdh: Add test computing shared_secret=basepoint with random inputs #1026

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merged 2 commits into from
Feb 11, 2022
Merged

ecdh: Add test computing shared_secret=basepoint with random inputs #1026

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c881dd4
ecdh: Add test computing shared_secret=basepoint with random inputs
real-or-random Dec 3, 2021
3531a43
ecdh: Make generator_basepoint test depend on global iteration count
real-or-random Feb 9, 2022
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35 changes: 34 additions & 1 deletion src/modules/ecdh/tests_impl.h
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Original file line number Diff line number Diff line change
Expand Up @@ -60,7 +60,7 @@ void test_ecdh_generator_basepoint(void) {

s_one[31] = 1;
/* Check against pubkey creation when the basepoint is the generator */
for (i = 0; i < 100; ++i) {
for (i = 0; i < 2 * count; ++i) {
secp256k1_sha256 sha;
unsigned char s_b32[32];
unsigned char output_ecdh[65];
Expand Down Expand Up @@ -123,10 +123,43 @@ void test_bad_scalar(void) {
CHECK(secp256k1_ecdh(ctx, output, &point, s_overflow, ecdh_hash_function_test_fail, NULL) == 0);
}

/** Test that ECDH(sG, 1/s) == ECDH((1/s)G, s) == ECDH(G, 1) for a few random s. */
void test_result_basepoint(void) {
secp256k1_pubkey point;
secp256k1_scalar rand;
unsigned char s[32];
unsigned char s_inv[32];
unsigned char out[32];
unsigned char out_inv[32];
unsigned char out_base[32];
int i;

unsigned char s_one[32] = { 0 };
s_one[31] = 1;
CHECK(secp256k1_ec_pubkey_create(ctx, &point, s_one) == 1);
CHECK(secp256k1_ecdh(ctx, out_base, &point, s_one, NULL, NULL) == 1);

for (i = 0; i < 2 * count; i++) {
random_scalar_order(&rand);
secp256k1_scalar_get_b32(s, &rand);
secp256k1_scalar_inverse(&rand, &rand);
secp256k1_scalar_get_b32(s_inv, &rand);

CHECK(secp256k1_ec_pubkey_create(ctx, &point, s) == 1);
CHECK(secp256k1_ecdh(ctx, out, &point, s_inv, NULL, NULL) == 1);
CHECK(secp256k1_memcmp_var(out, out_base, 32) == 0);

CHECK(secp256k1_ec_pubkey_create(ctx, &point, s_inv) == 1);
CHECK(secp256k1_ecdh(ctx, out_inv, &point, s, NULL, NULL) == 1);
CHECK(secp256k1_memcmp_var(out_inv, out_base, 32) == 0);
}
}

void run_ecdh_tests(void) {
test_ecdh_api();
test_ecdh_generator_basepoint();
test_bad_scalar();
test_result_basepoint();
}

#endif /* SECP256K1_MODULE_ECDH_TESTS_H */