Blockstream and Thales launch Bitcoin custody system built around offline signing
Blockstream has introduced a new institutional custody system for Bitcoin that keeps private keys offline, developed in partnership with Thales.
The product pairs Thales hardware security modules with Blockstream's Secure Multi-Party Computation technology, allowing institutions to approve transactions while sensitive key material remains sealed inside dedicated hardware. Announced on Friday, November 13, 2026, the system addresses growing concerns about AI-assisted cyberattacks targeting large Bitcoin holdings.
Secure Multi-Party Computation
The system uses Secure-MPC technology, which splits signing authority into shares rather than relying on a single private key. Multiple parties must collaborate to produce a valid signature, ensuring no single share can move funds. The transaction signing protocol runs entirely within Thales Hardware Security Modules (HSMs), meaning private keys and MPC key shares never cross the hardware boundary during signing.
Enterprise Focus
The custody system targets custodial banks, prime brokers, and other institutional users with features including policy controls, segregated accounts, multisignature options, and cryptographic audit trails. Blockstream Enterprise supports various signing models, including air-gapped setups and multisignature systems.
This launch is part of Blockstream's broader enterprise push, with its custody and tokenization services currently in beta with select private clients since Q3 2026. The company demonstrated the full security architecture at the Digital Assets Forum in New York on the same day as the announcement.
Security Philosophy
Blockstream co-founder Adam Back advocates for simpler, offline security models, arguing that fewer moving parts create fewer vulnerabilities. The company believes hardware isolation provides stronger protection against increasingly sophisticated AI-driven attacks that can find vulnerabilities faster and craft more convincing phishing attempts.
For institutions, the system addresses operational risk concerns by providing verifiable protection methods that speak directly to regulators and auditors. Blockstream positions this as a way to build trust with institutional investors who may have hesitated due to security concerns.
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