This library provides classes for digital signature creation and verification using the OpenSSL library. It includes two main classes: signer for creating signatures and verifier for verifying signatures.

• ES256 (ECDSA with SHA-256) signature creation and verification
• Support for CBOR-encoded data
• Easy-to-use interface for signing and verifying multiple data chunks

• C++17 or later
• OpenSSL library
• nlohmann/json library (for JSON and CBOR handling)

The signer class is used to create digital signatures.

// Create a signer object with a private key
signer s(std::string_view(private_key));

// Sign data
std::vector<uint8_t> data1 = {...};
std::vector<uint8_t> data2 = {...};
auto signature = s.sign(data1, data2);

// Check if signature was created successfully
if (signature) {
    // Use the signature
} else {
    // Handle error
}

The verifier class is used to verify digital signatures.

// Create a verifier object with a public key
verifier v(std::string_view(public_key));

// Verify a signature
std::vector<uint8_t> data1 = {...};
std::vector<uint8_t> data2 = {...};
std::vector<uint8_t> signature = {...};

bool is_valid = v.verify(signature, data1, data2);

if (is_valid) {
    // Signature is valid
} else {
    // Signature is invalid
}

The provided test_brute_force_attack function demonstrates how to use the signer and verifier classes:

1. Generate an ES256 key pair
2. Create a signer and verifier with the respective keys
3. Create a sample CWT (CBOR Web Token)
4. Sign the CBOR-encoded data
5. Verify the signature
6. Perform a brute-force attack simulation

• The library uses ECDSA with SHA-256 (ES256) for signing and verification.
• Error handling is done through exceptions in the constructors and optional return values for signing operations.
• The verifier's verify method is marked with [[nodiscard]] to encourage checking the return value.
• The library supports signing and verifying multiple data chunks in a single operation.

• Ensure that private keys are kept secure and not exposed in your code.
• Use strong, randomly generated keys for production use.