Abstract: The reliability of a second public key which is part of a second key pair generated in association with a first key pair is certified. A generating apparatus 210 provides certification data to a receiving apparatus 220 (S301). The receiving apparatus 220 transmits a certification request requesting a certification that the second public key PK2 is in a parent-child relationship with the first public key PKI to a certifying apparatus 230 (S302). In this example, the certification request includes the certification data, but if the certification data is provided directly from the generating apparatus 210 to the certifying apparatus 230, the certification request does not need to include the certification data. The certifying apparatus 230 verifies the certification data by calculating a verification formula for the certification data in response to the certification request (S303).

Abstract: Proving reliability of a second public key of a second key pair generated in association with a first key pair. A generator 210 calculates and stores x·H(n) which is proof data and ax·H(n), when the second public key ax·g1 which is of the second key pair is generated (S301). The generator 210 provides the calculated proof data to a receiving apparatus 220 (S302) which has received the proof data, transmits a proof request to the proving apparatus 230 for requesting a proof that the second public key ax·g1 is generated by an owner of the first public key a·g1 (S303). In response to the proof request, the proving apparatus 230 verifies the proof data by calculating a verification formula for the proof data (S304). The proving apparatus 230 transmits the verification result as a response to the proof request from the receiving apparatus 220 (S305).

Abstract: Signature handling for a block for which consensus was formed in blockchain network which requires signatures from plurality of nodes to form consensus for block adoption. After completion of the setup, first node 110 sends a first message including a generated block to N nodes (S301). Each node evaluates the validity of the block on basis of the rule for consensus formation (S302). If the block is valid, the node sends a second message which includes signature si, by secret key share f(xi), with respect to a hash value h of the block for which consensus is to be formed (S303-1). After k signatures are collected at jth node, the node merges these signatures to generate a signature corresponding to a public key PK (S304). A block for which consensus is to be formed has signature SK·h appended thereto and is added to blockchain of each node (S306).

Abstract: A method of recordation request of a compound transaction to a blockchain distributed network, comprising steps of: the first node constituting the distribution network signing a compound transaction in which a plurality of sources of assets exist by a secret key of the node, when there is a remaining source by which the compound transaction needs to be signed, the first node transmitting the compound transaction to a second node constituting the distributed network, and when there is no remaining source by which the compound transaction needs to be signed, the first node transmitting the compound transaction to a third node constituting the distributed network to request recordation to the distributed network.

Abstract: A consensus building method suitable when f Byzantine failure nodes (f is an integer equal to or larger than 1 and smaller than N/3) are assumed in a network having N nodes (N is an integer equal to or larger than 1) participating in consensus building, comprising the steps of: receiving a first message from other node which communicates that the other node determined a message including data subject to consensus building valid as a proposal, when the number of received first messages reach a predetermined value Q, transmitting a second message to each node which communicates that it is accepting the proposal, and when the number of received first messages do not reach the predetermined value Q, transmitting a third message to each node which communicates that it is dismissing the proposal, when the number of received second messages reach a predetermined value Q, transmitting a fourth message to each note which communicates that it is treating the proposal as agreed in the network, and when the number of rec