Google Pitches Banks on Splitting Crypto Keys Across Clouds With New Custody Service

Banks weighing crypto custody got a new option from Google Cloud on Wednesday: Google Multi-Party Compute, a key-signing service Google showcased at what it billed as its first event devoted to digital assets. The company’s pitch is that a bank can spread control of a key across several environments, so no single provider, Google included, holds all of it.

A bank could hold one share on its own hardware, one in Google Cloud and one at a rival cloud provider, Google said, adding that it can’t read customers’ key shares in plaintext, even those kept on its own servers. The service is in private preview, and Google’s documentation describes it as a platform that combines threshold signing with transaction policies and governance controls.

“Digital asset adoption and tokenization are at an inflection point. As regulated financial institutions begin adopting blockchains and tokenization, they need scalable, proven infrastructure to secure their clients’ assets,” said Rich Widmann, director of digital assets strategy at Google Cloud.

The product’s release notes log preview updates going back to August. Google said unnamed banks and other early partners are running it in tests, and that its parent, Alphabet, has started using the service for its own Ethereum and Solana holdings. General availability is targeted for early 2027; Google gave no pricing.

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Each share is created and stored by a separate party on its own secure hardware, and the parties cooperate to sign without ever assembling the full key. According to the docs, an attacker “who compromises fewer parties than the signing threshold can’t forge a signature or reconstruct the key.” Customers set the threshold, and Google offered 2-of-3 and 5-of-7 as examples.

A policy engine, which Google said runs in its Confidential Space environment, checks each transaction against rules such as spending caps and approved destinations. The docs describe that verdict as advisory: it “guides Signers but doesn’t enforce the final decision,” and enough Signers can override a denial and push the transaction through.

That puts Google up against BitGo, Fordefi and Fireblocks, which already sell institutions the tools to secure and approve blockchain transactions. Fireblocks, whose embedded-wallets head co-founded Dynamic, says many people already use a crypto wallet without knowing it.

Google is framing the service around AI and quantum risk, but the threats its documentation lists are more familiar ones: stolen or misused keys, outages and lost key material. Google said the system can be upgraded to post-quantum signing as blockchains adopt quantum-resistant cryptography, though it did not say when. Coinbase has urged Bitcoin developers to make sure a quantum-resistant upgrade works for large custodians.

Google said ECDSA, used by Bitcoin and Ethereum, and Ed25519, used by Solana, will both be supported at general availability. The overview page still marks Solana “coming soon,” while an Oct. 1 release note added distributed signing that uses Ed25519’s standard challenge hashing.

Related Listen: Bitcoin Custody Has 5 Levels. Where Should Your Keys Actually Live?

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