Blockstream and Thales launch Bitcoin custody system built around offline signing

Adam Back's company is betting institutions want hardware-locked keys and simpler security as cyberattacks grow more sophisticated

Blockstream has rolled out a new institutional custody system for Bitcoin. Its core idea is pleasantly old-fashioned: keep the keys away from the internet.

The product was built with French technology group Thales and announced on Friday, November 13, 2026. It pairs Thales hardware security modules with Blockstream’s own Secure Multi-Party Computation technology. The pitch is that institutions can approve transactions while sensitive key material stays sealed inside dedicated hardware.

The timing is deliberate. Blockstream co-founder Adam Back has been arguing for simpler, offline security models, especially as AI-assisted cyberattacks become a bigger worry for anyone holding Bitcoin at scale.

How the system works

Secure Multi-Party Computation, which Blockstream brands as Secure-MPC, adds another layer. Instead of a single private key, the signing authority is split into shares. Several parties then work together to produce a valid signature, and no single share is enough to move funds.

The notable design choice is where the signing happens. Blockstream says the entire transaction signing protocol runs inside the Thales HSMs. That means private keys and MPC key shares never cross the hardware boundary during signing.