Method and system for settling a blockchain transaction

A system for settling a transaction concerning an asset and being registered by forming part of a blockchain-based ledger for said asset, which ledger is arranged to keep track of transactions concerning the asset in question from senders to specified asset addresses, which transactions are signed using a private cryptographic key belonging to the sender in question, wherein the system comprises a central server, arranged to identify a seller, being associated with a seller address and a buyer, being associated with a buyer address, of the said asset, at a specified price;

• to produce a transaction identifier;
• to calculate, based upon the seller address or corresponding public key, the buyer address or corresponding public key, and the transaction identifier, a transaction-unique 1-of-2 multi-signature address capable of being activated by a respective private key of both the seller and the buyer, which respective private key corresponds to said respective public key;
• to monitor and verify, on the ledger, a first transaction of the asset to the multi-signature address signed by the seller;
• to monitor and verify, on the ledger, a second transaction of the asset from the multi-signature address to the buyer address signed by the buyer;
• to verify the first and second transactions;
• and to settle the said price between the buyer and seller.

A non-transitory computer readable medium storing a computer program product for automatically partaking as a trading party in a transaction concerning an asset and being registered by forming part of a blockchain-based ledger for said asset, which ledger is arranged to keep track of transactions concerning the asset in question from senders to specified asset addresses, which transactions are signed using a private cryptographic key belonging to the sender in question, wherein the computer program product is arranged to, electronically, to a central server signal interest on behalf of an interested user to trade the said asset, at a particular price, identifying to the central server the user by a blockchain address or corresponding public key;

• to receive, from the central server, both a blockchain address or a corresponding public key identifying a counterpart user and a transaction identifier;
• to calculate, based upon both the said addresses or corresponding public keys and the said transaction identifier, a transaction-unique multi-signature address capable of being activated by a respective private key of both the interested and the counterpart user, which respective private key corresponds to said respective public key;
• in case the trade relates to a selling of the asset, to sign a first transaction of the asset to the multi-signature address;
• and, in case the trade instead relates to a buying of the asset, to sign a second transaction of the asset from the multi-signature address to the buyer address.