From Decrypt · By André Beganski
In brief
Trezor is preparing for the UX challenges of a post-quantum Bitcoin, where SHRINCS, the community’s leading candidate signature scheme, lets users choose efficient “stateful” signatures that can expose funds to theft if reused beyond a signing budget, CTO Tomáš Sušánka said.
To reduce that risk, Trezor is considering making larger, safer “stateless” signatures the default and hiding the riskier stateful option behind advanced settings.
He also noted devices themselves need post-quantum upgrades for firmware and authentication.
Bitcoin custody has always involved some degree of risk, but wallet manufacturers like Trezor—which build physical devices designed to keep a user’s private keys secure offline—are preparing for a post-quantum world where new challenges arise.
That’s because SHRINCS, the community’s leading candidate for a post-quantum signature scheme, allows users to make transactions using stateful signatures that require rigid state tracking to prevent funds from being stolen, according to Trezor CTO Tomáš Sušánka.
Proposed late last year by Blockstream Research Director Jonas Nick and cryptographer Mikhail Kudinov, SHRINCS centers on a composite hash-based approach: users can make transactions using either stateful signatures or stateless signatures.
PredictCryptoBTC Highs in November
80,00042%YesNo82,50010%YesNo85,0007%YesNo87,5004%YesNo90,0002%YesNo+6 more outcomes+5 more outcomesNEW$205.05 volumeCloses: Dec 1, 2026, 04:59 UTCCloses: Dec 1, 2026, 04:59 UTCStateless signatures are quite large—potentially affecting fees, signature speed, and other efficiency metrics—but are safe to reuse, while smaller, more efficient stateful signatures come with serious security risks when reused beyond a particular signing budget.
The stateful component of SHRINCS is made up of a tree of one-time signatures, and if these keys are accidentally used more than once, enough cryptographic information is revealed for someone else to forge that user’s signature and effectively steal funds.
If Bitcoin successfully adopts SHRINCS, maintaining a meticulous count of the wallet’s state will become a critical responsibility for wallet developers—with lots of potential edge-case security risks.
“You’re giving them an option to mess up,” Sušánka said during a recent episode of MARA Foundation TV, in reference to state tracking. “It’s our job to make it in a secure way, right? It shouldn't be the user’s job.”
To mitigate this risk, Trezor is weighing options for how to support secure UX in a post-quantum world. For instance, Sušánka said the company is considering making the heavier, slower stateless signatures the default setting for all users, tucking the riskier stateful option behind an advanced settings wall.