Public key generation unit tests #541

I'm working on a project that utilizes this library to generate an ecc public key based on a private key. It's very likely I am misunderstanding how to use this library and/or c++, but I was looking for a reference example of a unit test to verify that the generated public key is correct. Maybe someone can point me in the right direction. Here's what I'm trying to do, but it doesn't seem to be generating the correct public key:

BOOST_AUTO_TEST_CASE(test_importprivkey)
{
    KeyPair keypair;
    unsigned char priv_key[KeyPair::PRIVATE_KEY_SIZE_BYTES] = {0x18,0xE1,0x4A,0x7B,0x6A,0x30,0x7F,0x42,0x6A,0x94,0xF8,0x11,0x47,0x01,0xE7,0xC8,0xE7,0x74,0xE7,0xF9,0xA4,0x7E,0x2C,0x20,0x35,0xDB,0x29,0xA2,0x06,0x32,0x17,0x25};
    unsigned char expected_pub_key[KeyPair::PUBLIC_KEY_SIZE_BYTES] = {0x04,0x50,0x86,0x3A,0xD6,0x4A,0x87,0xAE,0x8A,0x2F,0xE8,0x3C,0x1A,0xF1,0xA8,0x40,0x3C,0xB5,0x3F,0x53,0xE4,0x86,0xD8,0x51,0x1D,0xAD,0x8A,0x04,0x88,0x7E,0x5B,0x23,0x52,0x2C,0xD4,0x70,0x24,0x34,0x53,0xA2,0x99,0xFA,0x9E,0x77,0x23,0x77,0x16,0x10,0x3A,0xBC,0x11,0xA1,0xDF,0x38,0x85,0x5E,0xD6,0xF2,0xEE,0x18,0x7E,0x9C,0x58,0x2B,0xA6};
    keypair.ImportPrivKey(priv_key);

    BOOST_ASSERT(memcmp(expected_pub_key, &keypair.pub_key, KeyPair::PUBLIC_KEY_SIZE_BYTES) == 0);

}

My source code:

void KeyPair::ImportPrivKey(const unsigned char priv_key[KeyPair::PUBLIC_KEY_SIZE_BYTES])
{
    // TODO: pass this in as a parameter
    bool fCompressed = false;
    // TODO: validate the private key: any 256-bit number from 0x1 to 0xFFFF FFFF FFFF FFFF FFFF FFFF FFFF FFFE BAAE DCE6 AF48 A03B BFD2 5E8C D036 4140 is a valid private key

    secp256k1_context* ctx = secp256k1_context_create(SECP256K1_CONTEXT_SIGN);
    secp256k1_pubkey pubkey;
    // TODO: change member variable pub_key to be type secp256k1_pubkey and use that in the next function call
    int result = secp256k1_ec_pubkey_create(ctx, &pubkey, priv_key);

    unsigned char pubkey_buffer;
    size_t clen = KeyPair::PUBLIC_KEY_SIZE_BYTES;
    secp256k1_ec_pubkey_serialize(ctx, &pubkey_buffer, &clen, &pubkey, fCompressed ? SECP256K1_EC_COMPRESSED : SECP256K1_EC_UNCOMPRESSED);
    if(result != 0)
    {
        std::cerr << "Error in ImportPrivKey" << std::endl;
    }
}

#ifndef KEY_PAIR_H
#define KEY_PAIR_H

class KeyPair
{
    public:
        static const unsigned int PRIVATE_KEY_SIZE_BYTES            = 32;
        static const unsigned int PUBLIC_KEY_SIZE_BYTES             = 65;
        static const unsigned int PUBLIC_KEY_COMPRESSED_SIZE_BYTES  = 33;

        unsigned char priv_key[PRIVATE_KEY_SIZE_BYTES];
        unsigned char pub_key[PUBLIC_KEY_SIZE_BYTES];

        void ImportPrivKey(const unsigned char priv_key[PRIVATE_KEY_SIZE_BYTES]);
};

#endif //KEY_PAIR_H

pubkey_buffer needs to be 65 bytes at least. And you need to initialize clen to 65 or more.

@JBaczuk if it helps, we have quite a few test fixtures at https://github.com/bitcoinjs/tiny-secp256k1/blob/6c1827840881e9b4b4b2aa42cbe167d8a9522105/tests/fixtures/points.json that might be useful for verifying your libraries output.

Thanks, it looks like pubkey_buffer indeed matches, but pubkey.data doesn't. I thought pubkey_buffer was the serialized version, but I guess I don't understand exactly what that means in this context.

pubkey.data is opaque and has no meaning to users of the API.