Computer-implemented method and system for transferring access to a digital asset

Patent metadata

Field	Value
Publication number	US-12341908-B2
Application number	US-202418622826-A
Country	US
Kind code	B2
Filing date	Mar 29, 2024
Priority date	Apr 5, 2018
Publication date	Jun 24, 2025
Grant date	Jun 24, 2025

Abstract

A method of digitally signing a message is disclosed. The method comprises distributing first shares of a first secret value among a plurality of participants, wherein the first secret value is a private key accessible by means of a first threshold number of the first shares, and is inaccessible to less than the first threshold number of the first shares; distributing second shares of a second secret value among the participants, wherein the second secret value is an ephemeral key, wherein said ephemeral key is inaccessible to less than said first threshold number of said second shares; and distributing third shares of a third secret value among the participants, wherein each third share is adapted to be applied to a message to generate a respective fourth share of a fourth secret value, wherein the fourth secret value is the message signed with the private key and using the ephemeral key.

First claim

What is claimed is:

1. A method of transferring access to a digital asset, the method comprising:
providing each of a plurality of participants with a respective share of a second private key of a second private-public key pair of a cryptography system;
splitting the respective share of one of said participants is into a plurality of sub-shares, and deleting it;
receiving a first blockchain transaction from a first participant of said participants by each of a plurality of second participants of said participants, wherein said first participant has a first private key of a first private-public key pair of said cryptography system, and wherein said first blockchain transaction is signed with said first private key;
verifying, by a plurality of said second participants, that said first blockchain transaction has been signed with said first private key;
applying a respective said share of said second private key to said first blockchain transaction to generate a respective share of a first secret value, wherein said first secret value is a second blockchain transaction signed with said second private key, wherein said first secret value is accessible to a first threshold number of said shares of said first secret value and is inaccessible to less than said first threshold number of shares of said first secret value; and
combining at least said first threshold number of said shares of said first secret value from said first participant and a plurality of said second participants to generate said first secret value.

2. The method according to claim 1 , wherein one of said sub-shares is stored at one of the other participants.

3. The method according to claim 1 , wherein each of a plurality of said second participants has a respective private key of the cryptography system.

4. The method according to claim 1 , further comprising distributing shares of a said share of said second private key in possession of said first participant among said first participant and at least one said second participant.

5. The method according to claim 1 , further comprising transferring access to said digital asset to a third private key of said cryptography system in an event of a said second participant becoming unresponsive.

6. The method according to claim 5 , wherein the digital asset remains under control of said third private key for a predetermined time.

7. The method according to claim 1 , further comprising distributing said shares of said second private key among a plurality of said participants.

8. A method of transferring access to a digital asset, the method comprising:
providing each of a plurality of participants with a respective share of a second private key of a second private-public key pair of a cryptography system;
splitting the respective share of one of said participants is into a plurality of sub-shares, and deleting it;
sending a first blockchain transaction from a first participant to a plurality of second participants, wherein said first participant has a first private key of a first private-public key pair of said cryptography system, wherein said first blockchain transaction is signed with said first private key, wherein the respective share of one of said participants is split into a plurality of sub-shares, after which it is deleted;
receiving, from a plurality of said second participants, a respective share of a first secret value, wherein said first secret value is a second blockchain transaction signed with said second private key, wherein said first secret value is accessible to a first threshold number of said shares of said first secret value and is inaccessible to less than said first threshold number of shares of said first secret value, wherein each said share of said second private key is applied to said second blockchain transaction after verification, by the corresponding said second participants, that said first blockchain transaction has been signed with said first private key; and
combining at least said first threshold number of said shares of said first secret value from said first participant and a plurality of said second participants to generate said first secret value.

9. The method according to claim 8 , wherein one of said sub-shares is stored at one of the other participants.

10. The method according to claim 8 , wherein the method further comprises at least one of:
each of a plurality of said second participants has a respective private key of the cryptography system; or
distributing shares of a said share of said second private key in possession of said first participant among said first participant and at least one said second participant.

11. The method according to claim 8 , further comprising transferring access to said digital asset to a third private key of said cryptography system in an event of a said second participant becoming unresponsive.

12. The method according to claim 11 , wherein the digital asset remains under control of said third private key for a predetermined time.

13. The method according to claim 8 , further comprising distributing said shares of said second private key among a plurality of said participants.

14. The method according to claim 8 , wherein the cryptography system is an elliptic curve cryptography system, wherein a respective public key is related to a corresponding private key of the first and second public-private key pairs by multiplication of an elliptic curve generator point of the corresponding private key.

15. A computer-implemented system for carrying out a method according to claim 1 .

16. A computer-implemented system for carrying out a method according to claim 1 .

Assignees

• Nchain Licensing Ag

Inventors

• Fletcher John
• Trevethan Thomas

Classifications

• H04L9/50

  using hash chains, e.g. blockchains or hash trees · CPC title

• H04L2209/56

  Financial cryptography, e.g. electronic payment or e-cash · CPC title

• H04L9/3236

  using cryptographic hash functions · CPC title

• H04L9/3066

  involving algebraic varieties, e.g. elliptic or hyper-elliptic curves · CPC title

• H04L9/085 Primary

  Secret sharing or secret splitting, e.g. threshold schemes · CPC title