Patent ID: 11943350
Assignee: COINBASE, INC.
Field: Digital communication (Electrical engineering)
Classification: CPC H | IPC H

Claim 7:
8. A system comprising:
an online computer system operating within an online computing environment; and
an offline computer system operating within an offline computing environment,
wherein the online computer system comprises one or more first processors and memory storing instructions that, when executed by the one or more first processors, cause first operations comprising:
receiving a blockchain transaction to be signed and obtaining, based on a key shard threshold, signing key shards corresponding to a signing private key from a plurality of account managers, each of the plurality of account managers storing a different one of the signing key shards, the key shard threshold being (i) a number of key shards required for reconstructing the signing private key and (ii) less than a number of key shards derived from the signing private key using a ceremony key; and
storing the signing key shards and the blockchain transaction at a removable computer-readable storage medium, and

wherein the offline computer system comprises one or more second processors and memory storing instructions that, when executed by the one or more second processors, cause second operations comprising:
obtaining, from the removable computer-readable storage medium, the signing key shards and the blockchain transaction;
forming a ciphertext of the signing private key using the signing key shards that satisfy the key shard threshold;
reconstructing, in the offline computing environment, the signing private key by obtaining the ceremony key from a hardware security module (HSM) and decrypting the ciphertext, derived from the signing key shards that satisfy the key shard threshold, using the ceremony key, wherein the ceremony key is a same symmetric private key previously used to encrypt the signing private key to generate a prior ciphertext from which the signing key shards were derived; and
signing, in the offline computing environment, the blockchain transaction using the signing private key.