Abstract: The invention relates to a method for documenting subjects using hash chains. The method includes receiving a subject data write request including one or more subject attribute values, generating a fingerprint from a current last block of a hash chain, and generating a payload from the subject data, the payload including the one or more subject attribute values and one or more keys identifying the one or more subject attribute values. The method further includes appending a block to the hash chain. The appended block includes the payload and the fingerprint.

Abstract: The invention relates to a method for documenting subjects using hash chains. The method includes receiving a subject data write request including one or more subject attribute values, generating a fingerprint from a current last block of a hash chain, and generating a payload from the subject data, the payload including the one or more subject attribute values and one or more keys identifying the one or more subject attribute values. The method further includes appending a block to the hash chain. The appended block includes the payload and the fingerprint.

Abstract: The invention relates to a method for overseeing execution of graph-based contracts using hash chains. The method includes obtaining a graph-based contract. The graph-based contract is configured to enforce a contract for performing a transaction between at least two parties. The method also includes obtaining event data associated with an execution of the graph-based contract, and performing, governed by the graph-based contract, a first state transition from a first state to a second state by making a determination that a first state transition criterion is met by the event data, with the first state transition connecting the second state to the first state, and based on the determination transitioning to the second state. The method further includes appending a first block to a hash chain. The first block includes a documentation of the first state transition.