US Patent 10425225 Synchronizable hardware security module

An HSM cluster includes a set of hardware security modules that maintain a set of cryptographic keys that are synchronized across the HSM cluster. Individual applications running on client computer systems access the HSM cluster using HSM cluster clients running on the client computer systems. The HSMs are accessed via a set of HSM cluster servers that monitor the synchronization of the cryptographic keys. Synchronization of the HSMs is maintained by the HSM cluster clients. The HSM cluster clients replicate key-addition and key-deletion operations across the HSM cluster. When a new key is created by a particular HSM, a prefix associated with the particular HSM is added to the identifier associated with the new key to avoid key-namespace collisions. If the set of cryptographic keys becomes unsynchronized across the HSM cluster, applications may continue read-only cryptographic operations while the HSM cluster is resynchronized by the HSM cluster clients.