Patent ID: 11968304
Assignee: NCHAIN LICENSING AG
Field: Digital communication (Electrical engineering)
Classification: CPC H | IPC H

Claim 19:
20. A computer system for generating at least one challenge transaction comprising one or more computers programmed to:
create at least one challenge transaction for recording in a blockchain maintained by a blockchain network, wherein the at least one challenge transaction comprises an r-challenge corresponding to an unknown ephemeral key, wherein each participant of a set of keyshare participants holds an ephemeral key share of the unknown ephemeral key;
wherein the at least one challenge transaction cause a node of the blockchain network, in response to receiving at least one proof transaction indicating the r-challenge of the at least one challenge transaction, to apply a signature verification function of an Elliptic Curve Digital Signature Algorithm, ECDSA, to: (i) an s-part of the at least one proof transaction, and (ii) one of:
(iia) an r-part of the r-challenge, and in that event the verification of the signature fails if the s-part of the at least one proof transaction not correspond to the unknown ephemeral key, or
(iib) an r-part of the at least one proof transaction, and in that event the node is further caused to check that the r-part of the at least one proof transaction satisfies the r-challenge, whereby the check fails if the r-part of the at least one proof transaction does not satisfy the r-challenge and thus does not correspond to the unknown ephemeral key;
wherein the r-challenge for the at least one challenge transaction is derived from a plurality of public ephemeral key components held in computer memory accessible thereto.