Merge pull request #31 from apoelstra/2018-10-commit-fix

Fix pedersen commitment serialization after #30 broke it

src/modules/generator/tests_impl.h

@@ -190,8 +190,28 @@ void test_generator_generate(void) {
     }
 }
 
+void test_generator_fixed_vector(void) {
+    const unsigned char two_g[33] = {
+        0x0b,
+        0xc6, 0x04, 0x7f, 0x94, 0x41, 0xed, 0x7d, 0x6d, 0x30, 0x45, 0x40, 0x6e, 0x95, 0xc0, 0x7c, 0xd8,
+        0x5c, 0x77, 0x8e, 0x4b, 0x8c, 0xef, 0x3c, 0xa7, 0xab, 0xac, 0x09, 0xb9, 0x5c, 0x70, 0x9e, 0xe5
+    };
+    unsigned char result[33];
+    secp256k1_generator parse;
+
+    CHECK(secp256k1_generator_parse(ctx, &parse, two_g));
+    CHECK(secp256k1_generator_serialize(ctx, result, &parse));
+    CHECK(memcmp(two_g, result, 33) == 0);
+
+    result[0] = 0x0a;
+    CHECK(secp256k1_generator_parse(ctx, &parse, result));
+    result[0] = 0x08;
+    CHECK(!secp256k1_generator_parse(ctx, &parse, result));
+}
+
 void run_generator_tests(void) {
     test_shallue_van_de_woestijne();
+    test_generator_fixed_vector();
     test_generator_api();
     test_generator_generate();
 }

src/modules/rangeproof/main_impl.h

@@ -73,7 +73,7 @@ int secp256k1_pedersen_commitment_serialize(const secp256k1_context* ctx, unsign
 
     secp256k1_pedersen_commitment_load(&ge, commit);
 
-    output[0] = 11 ^ secp256k1_fe_is_quad_var(&ge.y);
+    output[0] = 9 ^ secp256k1_fe_is_quad_var(&ge.y);
     secp256k1_fe_normalize_var(&ge.x);
     secp256k1_fe_get_b32(&output[1], &ge.x);
     return 1;

src/modules/rangeproof/tests_impl.h

@@ -672,10 +672,30 @@ void test_rangeproof_fixed_vectors(void) {
     ));
 }
 
+void test_pedersen_commitment_fixed_vector(void) {
+    const unsigned char two_g[33] = {
+        0x09,
+        0xc6, 0x04, 0x7f, 0x94, 0x41, 0xed, 0x7d, 0x6d, 0x30, 0x45, 0x40, 0x6e, 0x95, 0xc0, 0x7c, 0xd8,
+        0x5c, 0x77, 0x8e, 0x4b, 0x8c, 0xef, 0x3c, 0xa7, 0xab, 0xac, 0x09, 0xb9, 0x5c, 0x70, 0x9e, 0xe5
+    };
+    unsigned char result[33];
+    secp256k1_pedersen_commitment parse;
+
+    CHECK(secp256k1_pedersen_commitment_parse(ctx, &parse, two_g));
+    CHECK(secp256k1_pedersen_commitment_serialize(ctx, result, &parse));
+    CHECK(memcmp(two_g, result, 33) == 0);
+
+    result[0] = 0x08;
+    CHECK(secp256k1_pedersen_commitment_parse(ctx, &parse, result));
+    result[0] = 0x0c;
+    CHECK(!secp256k1_pedersen_commitment_parse(ctx, &parse, result));
+}
+
 void run_rangeproof_tests(void) {
     int i;
     test_api();
     test_rangeproof_fixed_vectors();
+    test_pedersen_commitment_fixed_vector();
     for (i = 0; i < 10*count; i++) {
         test_pedersen();
     }