Class Key

Compresses an uncompressed public key using the elliptic curve secp256k1. This method takes a public key in its uncompressed form and returns a compressed representation of the public key. Elliptic curve public keys can be represented in a shorter form known as compressed format which saves space and still retains the full public key's capabilities. The method uses the elliptic library to convert the uncompressed public key into its compressed form.

The steps involved in the process are:

1. Initialize a new elliptic curve instance for the secp256k1 curve.
2. Create a key pair object from the uncompressed public key buffer.
3. Extract the compressed public key from the key pair object.
4. Return the compressed public key as a Buffer object.

Throws

Error Throws an error if the provided public key cannot be compressed, typically indicating that the key is not valid.

Converts a 33-byte Bitcoin public key to a 32-byte x-only public key as used in Taproot. This function checks if the provided public key buffer is already 32 bytes long, in which case it returns the buffer unchanged. If the buffer is 33 bytes long, it assumes that the first byte is the parity byte used for indicating the y-coordinate in traditional SEC1 encoding and removes this byte, thereby converting the public key to an x-only format suitable for use with Bitcoin's Taproot.

Adopted from https://github.com/ACken2/bip322-js/pull/6 by Czino

Throws

If the public key is neither 32-byte nor 33-byte long

Uncompresses a given public key using the elliptic curve secp256k1. This method accepts a compressed public key and attempts to convert it into its uncompressed form. Public keys are often compressed to save space, but certain operations require the full uncompressed key. This method uses the elliptic library to perform the conversion.

The function operates as follows:

1. Initialize a new elliptic curve instance using secp256k1.
2. Attempt to create a key pair from the compressed public key buffer.
3. Extract the uncompressed public key from the key pair object.
4. Return the uncompressed public key as a Buffer object. If the compressed public key provided is invalid and cannot be uncompressed, the method will throw an error with a descriptive message.

Throws

Error Throws an error if the provided public key cannot be uncompressed, typically indicating that the key is not valid.