Reusable Taproot Addresses

Documentation

This work is still in progress. Do not use this library on mainnet.

Currently it implements the steps described in Inital Transaction section of "Reusable taproot addresses" document.

But instead of calculating the addresses, both sender and receiver functions return the key that can be used to derive the addresses. This was suggested in this comment.

Sender function (generate_master_extended_public_key) returns a public key, which must be used as a master extendend public key to derive all addresses to send coins.

Receiver function (generate_master_extended_private_key) returns a private key, which must be used as a master extendend private key to derive all addresses to receive coins.

1. The first step is to calculate the change address of the sender and the relationship_seed that the sender will share with the receiver.

pub fn sender::generate_change_output_script(sender_secret_key: &SecretKey, receiver_pub_key: &PublicKey) -> (PublicKey, [u8; 32]);

The sender_secret_key must be the private key associated with the input with the lowest index, belonging to the sender.

The receiver_pub_key must be the public key of the Taproot address used by the receiver.

This function returns a tuple. The first element is the PublicKey of the change address and the second is the 32-byte relationship seed ([u8; 32]).

2. The sender can now calculate the addresses that can be used to send funds to the recipient.

pub fn sender::generate_master_extended_public_key(relationship_seed: &[u8; 32], receiver_pub_key: &PublicKey) -> Vec<PublicKey>;

The relationship_seed was calculated in the first step and must be used to derive the public keys.

The receiver_pub_key must be the public key of the Taproot address used by the receiver.

The function returns a list of public keys (PublicKey) that will be used as a master public key to derive the addresses to send coins.

3. Likewise, the receiver can calculate the same addresses, watches them and react to the received transaction.

pub fn receiver::generate_master_extended_private_key(P_change_sender: &PublicKey, sender_pub_key: &PublicKey, receiver_secret_key: &SecretKey) -> Vec<PublicKey>;

The P_change_sender must be the public key of the change address of the sender calculated in the fist step (the first element of the tuple returned by the sender::generate_change_output_script function).

The sender_pub_key must be the public key associated with the input with the lowest index, belonging to the sender.

The receiver_secret_key must be the private key of the Taproot address used by the receiver.

The function returns a list of public keys (SecretKey) that will be used as a master private key to derive all addresses to receive coins.

❗ The public key returned by sender::generate_master_extended_public_key must be the same as the one calculated from the private key returned by receiver::generate_master_extended_private_key.