Google Previews a Multi-Party Computation Custody Service That Splits Bank Signing Keys Across Rival Clouds

Google used a digital-assets symposium in New York on October 28 to preview Google Multi-Party Compute, a custody system that splits private signing keys across separate environments. Several banks are testing it before a planned launch in early 2027. Google has not disclosed pricing.

The design uses multi-party computation (MPC), a cryptographic method in which several parties jointly produce a signature without ever assembling the full key. According to Unchained and other reports, a bank could hold one key share on its own hardware, a second in Google Cloud and a third with a competing cloud provider. Institutions can set signing thresholds such as two of three or five of seven. Before any signature, a policy engine running inside Google's Confidential Space (an isolated, attested computing environment) checks each transfer against spending limits, destination restrictions and approval rules.

Google says it cannot access key shares in unencrypted form. Alphabet has begun securing its own digital assets with the system. The product targets credential theft and unauthorized transfers, which have caused most recent large custody losses. It does not address a failure of the underlying signature cryptography. Standard threshold signatures for Bitcoin and Ethereum still rely on elliptic-curve schemes that a large quantum computer could break.