Signature-based atomic swap

A method performed by a first party, the method comprising:

• generating a template of a first transaction having an input based on an output from a prior transaction associated with a second party;
• generating a message based on the template of the first transaction;
• generating a secret based on the message;
• generating a value based on the secret, wherein the secret cannot be derived from the value;
• generating a first puzzle transaction, wherein a first locking script of the first puzzle transaction comprises a knowledge proof configured to require an unlocking script to comprise the secret;
• publishing the first puzzle transaction to a first blockchain;
• receiving a signature from the second party, wherein the signature is created by the second party using the value based on the secret;
• including the signature in the unlocking script of the first transaction and then sending the first transaction to a second blockchain.

A method comprising:

• obtaining, by a second party, a value generated by a first party based on a secret, wherein the secret cannot be derived from the value, wherein the secret is based on a message generated by the first party based on a template of a first transaction, and wherein the template of the first transaction has an input based on an output from a prior transaction associated with the second party;
• signing, by the second party, the value based on the secret to create a signature;
• sending the signature to the first party from the second party, wherein the first party includes the signature in an unlocking script of the first transaction and then sends the first transaction to a second blockchain;
• determining, by the second party and from the first transaction on the second blockchain, the message and the secret;
• and
• creating, by the second party, a second transaction which unlocks a first output of a first puzzle transaction based on the secret, and submitting the second transaction to the first blockchain, wherein a first locking script of the first puzzle transaction comprises a knowledge proof configured to require an unlocking script to comprise the secret;
• wherein the template of the first transaction, the secret and the first puzzle transaction are generated by the first party.

Computer equipment, comprising:

• memory comprising one or more memory units;
• and
• processing apparatus comprising one or more processing units, wherein the memory stores code arranged to run on the processing apparatus, the code being configured so as when run on the processing apparatus, the processing apparatus performs a method performed in a system comprising a first party and a second party, the method comprising:
• generating, by the first party, a template of a first transaction having an input based on an output from a prior transaction associated with the second party;
• generating, by the first party, a message based on the template of the first transaction;
• generating, by the first party, a secret based on the message;
• generating, by the first party, a value based on the secret, wherein the secret cannot be derived from the value;
• generating, by the first party, a first puzzle transaction, wherein a first locking script of the first puzzle transaction comprises a knowledge proof configured to require an unlocking script to comprise the secret;
• publishing, by the first party, the first puzzle transaction to a first blockchain;
• obtaining, by the second party, the value based on the secret;
• signing, by the second party, the value based on the secret to create a signature;
• sending the signature from the second party to the first party;
• including, by the first party, the signature in the unlocking script of the first transaction and then sending the first transaction to a second blockchain;
• determining, by the second party and from the first transaction on the second blockchain, the message and the secret;
• and
• creating, by the second party, a second transaction which unlocks a first output of the first puzzle transaction based on the secret, and submitting the second transaction to the first blockchain.

A computer program embodied on non-transitory computer-readable storage media and configured as, when run on one or more processors, the one or more processors perform a method performed in a system comprising a first party and a second party, the method comprising:

• generating, by the first party, a template of a first transaction having an input based on an output from a prior transaction associated with the second party;
• generating, by the first party, a message based on the template of the first transaction;
• generating, by the first party, a secret based on the message;
• generating, by the first party, a value based on the secret, wherein the secret cannot be derived from the value;
• generating, by the first party, a first puzzle transaction, wherein a first locking script of the first puzzle transaction comprises a knowledge proof configured to require an unlocking script to comprise the secret;
• publishing, by the first party, the first puzzle transaction to a first blockchain;
• obtaining, by the second party, the value based on the secret;
• signing, by the second party, the value based on the secret to create a signature;
• sending the signature from the second party to the first party;
• including, by the first party, the signature in the unlocking script of the first transaction and then sending the first transaction to a second blockchain;
• determining, by the second party and from the first transaction on the second blockchain, the message and the secret;
• and
• creating, by the second party, a second transaction which unlocks a first output of the first puzzle transaction based on the secret, and submitting the second transaction to the first blockchain.