Abstract: A method, system and program enabling a third party to determine whether a first party and a second party agree on membership of a set of blockchain transactions transacting between the first and second party.

Abstract: A computer-implemented method of alerting users to on-chain events, wherein a primary user is associated with a primary user public key, and wherein the method is performed by an alerting entity and comprises: identifying one or more event transactions, wherein each event transaction comprising respective event data; generating a primary alert transaction, wherein the primary alert transaction comprises a first output locked to the primary user public key, and a second output comprising alert data, and wherein the alert data comprises a respective identifier of each identified event transaction; and transmitting the primary alert transaction to the blockchain network.