Registry and automated management method for blockchain-enforced smart contracts
The invention relates to the fields of tokenisation, blockchain and smart contract technologies. It provides a technical arrangement which simplifies the automated management of contracts. The invention comprises a method and system which use a computer-based repository for storage of the contract. The contract is then represented by a transaction on the blockchain. Metadata within the transaction's script includes a hash of the contract and a means of identifying its location within the repository. The transaction also includes an unspent output (UTXO) which indicates its status as an open (ie not terminated) contract. The contract is terminated by spending the output at a later point in time, for example, using n Lock Time+Check Lock Time Verify (CLTV). By combining this concept with other techniques and computing components, the invention can provide a powerful mechanism for implementing various tasks such as renewing or rolling over the contract, or dividing it into sub-contracts or conditions. Furthermore, as the status and existence of the contract is evidence via the blockchain, this provides a permanent, publicly visible and non-alterable record of the contract.
1. A computer-implemented method of controlling the visibility and/or performance of a contract, the method comprising:
(a) storing a contract on or in a computer-based repository;
(b) broadcasting a transaction to a blockchain, the transaction comprising:
i) at least one unspent output (UTXO); and
ii) metadata comprising an identifier indicative of a location where the contract is stored;
(c) interpreting the contract as open or valid until the unspent output (UTXO) is spent on the blockchain; and
(d) renewing or rolling the contract on by:
generating a new key using data relating to a previous key associated with the contract;
generating a script comprising the new key, the location of the contract and a hash of the contract; and
paying an amount of currency to a transaction comprising the script.
2. A method according to claim 1 wherein the transaction further comprises a deterministic redeem script address, wherein the redeem script address is a pay-to-script-hash (P2SH) address.
3. A method according to claim 2 and further comprising the step of terminating the contract by broadcasting a further transaction to the blockchain to spend the output (UTXO).
4. A method according to claim 3 wherein the further transaction comprises:
an input which is the output (UTXO); and
an unlocking script comprising a signature; the metadata; and a public key.
5. A method according to claim 1 wherein the contract defines:
i) at least one condition; and
ii) at least one action whose performance is dependent upon the evaluation of the condition; and/or
wherein the metadata comprises:
i) an address or representation of an address of where the contract is stored in the computer-based repository; and/or
ii) a hash of the contract.
6. A method according to claim 1 and comprising:
checking whether the contract has been terminated by determining whether the UTXO is in a list of unspent transaction outputs for the blockchain.
7. A method according to claim 1 , wherein:
i) the contract is stored in a Distributed Hash Table (DHT); and/or
ii) the method comprises:
broadcasting a transaction to the blockchain comprising an instruction to spend the output at a specified date and/or time, wherein the instruction is a ChecklockTimeVerify instruction.
8. A method according to claim 1 wherein:
i) access to some or all of the contents of the contract is restricted to at least one designated authorised party; and/or
ii) the contract comprises a Deterministic Finite Automaton (DFA) to implement the contract;
wherein the Deterministic Finite Automaton is defined using a codification scheme.
9. A method according to claim 8 wherein the Deterministic Finite Automaton is implemented using:
i) at least one blockchain transaction, using a scripting language;
ii) a computing agent arranged to monitor the state of the blockchain; and/or
iii) a set of instructions for a digital wallet.
10. A system, comprising:
one or more processors; and
memory storing instructions that, as a result of execution by the one or more processors, cause the system to:
(a) store a contract on or in a computer-based repository;
(b) broadcast a transaction to a blockchain, the transaction comprising:
i) at least one unspent output (UTXO); and
ii) metadata comprising an identifier indicative of a location where the contract is stored;
(c) interpret the contract as open or valid until the unspent output (UTXO) is spent on the blockchain; and
(d) renew or rolling the contract on by:
generating a new key using data relating to a previous key associated with the contract;
generating a script comprising the new key, the location of the contract and a hash of the contract; and
paying an amount of currency to a transaction comprising the script.