Nchain Licensing Ag

Michaella Pettit

Wei Zhang

Craig Steven Wright

Owen Vaughan

Chloe Ceren Tartan

Steven Patrick Coughlan

Alessio Pagani

A computer-implemented method of generating a share of a threshold signature, wherein a group of participants comprises a set of target participants and a set of dummy participants, wherein the number of target participants is less than the number of participants required to generate a valid signature, wherein each target participant and each dummy participants has i) a respective share of a first private key, ii) a respective share of an ephemeral private key, iii) a respective share of a first blinding key, iv) a respective share of a second blinding key, and wherein each target participant has v) an ephemeral public key corresponding to the ephemeral private key.

Threshold signature scheme

A computer-implemented method of proving that a target sub-group generated a digital signature, wherein the group is divisible into a plurality of unique sub-groups, each sub-group comprising at least the threshold number of participants. The method comprises: for each sub-group to which the first participant belongs, generating a first ephemeral private key share, wherein each other participant of each respective sub-group generates a respective ephemeral private key share; for each respective shared ephemeral private key, generating a respective shared ephemeral public key; generating a first signature share of the signature based on a first private key share, the first ephemeral private key share of a target one of the respective shared ephemeral private keys, and a message; and making the first signature share available to a coordinator for generating the signature.

Generating digital signatures

A computer-implemented method of generating a shared cryptographic key based on at least one shared secret, wherein each participant belonging to a first group has a respective share of a first secret, the first secret having a first threshold and a corresponding first public key, wherein a second coordinator has a second public key corresponding to a second secret, wherein the second coordinator is configured to generate the same shared cryptographic key.

Threshold key exchange

A computer-implemented method of requiring at least one of a sub-group of a group of participants to contribute to a threshold-optimal signature scheme, wherein the valid signature comprises a first signature component and a second signature component, wherein each participant has a respective private key share of a shared private key, a respective ephemeral private key share of a shared ephemeral private key, and the first signature component, wherein the shared private key can only be generated with at least a first threshold number of respective private key shares.

Nested threshold signatures

A public key may be recorded on the blockchain by a certificate authority in such a manner that any third party may quickly and easily verify that the public key is certified by the certificate authority and that the certification has not been revoked. The certificate authority may be able to revoke the certification nearly instantaneously, and/or may be able to simultaneously certify a new key for the same entity while revoking the old key. The verification may be incorporated into a new transaction so that there is no gap between reliance on the certificate and the verification of its validity. In some cases, each transaction in which the certificate is used may also serve as linked certificate transaction that renews the certificate to enable a subsequent use.

Methods and devices for automated digital certificate verification

A computer-implemented method of deriving keys of a hierarchical key structure, wherein the method is performed by a first party and comprises: generating a target index of a target child key, wherein the target index is generated based on a first result of inputting at least a target message to a first hash function; and deriving the target child key of a level in a hierarchy of a key structure based on a) a parent key of a preceding level in the hierarchy, and b) a second result of inputting at least i) the parent key, and ii) the target index, to a second hash function.

Key derivation method

A computer-implemented method of identifying a denial-of-service attack during a threshold signature scheme, wherein each participant has respective shares of first and second shared secrets, wherein the method is performed by a first participant of the group and comprises: calculating a first target share; calculating a target value based on the first target share and a first predetermined amount of other target shares; calculating a target public key corresponding to the target value; calculating a first verification share based on the first share of the first shared secret and a public key corresponding to the second shared secret; calculating a verification public key based on at least the first verification share and a second predetermined amount of other verification shares; and determining whether at least one other participant is attempting a denial-of-service attack based on whether the verification public key matches the target public key.

Identifying denial-of-service attacks

A computer-implemented method of generating a share of a digital signature of a message, wherein a threshold number of different signature shares from respective participants of a group of participants are required to generate the digital signature, wherein each participant has a respective private key share, the method being performed by a first one of the participants and comprising: generating a first message-independent component and a first message-dependent component, wherein the message-independent component is generated based on a first private key share and wherein the message-dependent component is generated based on the message; causing the first message-independent component to be made available to a coordinator; and causing a first signature share to be made available to the coordinator for generating the signature based on at least the threshold number of signature shares, wherein the first signature share comprises at least the message-dependent component.

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London, United Kingdom

Michaella Pettit