BTQ and QPerfect publish a gate-level design for quantum one-shot signatures
BTQ Technologies and its subsidiary QPerfect give explicit qubit and gate counts for a signing key that can only ever sign one message, before obfuscation.
Researchers at BTQ Technologies and its French subsidiary QPerfect have published an explicit quantum circuit for a "one-shot signature," a cryptographic key that can sign exactly one message and then becomes useless. The paper, A quantum algorithm for one-shot signatures, gives qubit and gate counts for the scheme and has been accepted for publication at ACM PQQS 2026, according to its arXiv listing.
What was announced
In an ordinary digital signature scheme, the secret key is a string of bits that can be copied and reused indefinitely. QPerfect's explainer frames the problem with delegation: if Alice wants Bob to approve one emergency software update on her behalf, handing him her key gives him unlimited power, and a public ledger that records key use can be tampered with. A one-shot signature replaces the classical secret key with a quantum state. Signing a message requires measuring that state, which destroys it, and the no-cloning theorem prevents making a backup copy beforehand.
The idea was introduced by Ryan Amos, Marios Georgiou, Aggelos Kiayias and Mark Zhandry in 2020, QPerfect notes. The new paper moves it from theory toward concrete quantum instructions.
The technical details
The scheme has two stages. Key generation produces a classical public key and a quantum secret key; signing processes that quantum key together with a message to produce a classical signature, which an ordinary computer can check. The paper says there is no algorithmic error in the construction. It works by preparing a superposition over the elements of a random affine coset determined by a puncturable pseudorandom function, along with a circuit that tests coset membership.
According to the abstract, the logical qubit count scales as Θ(κ log r + n + l) and gate complexity as Θ(n³ + nl), where l is the message length and κ the security parameter. Quantum Computing Report reports that single-bit signatures need between 206 and 2,438 logical qubits across the security parameters studied, and that the circuits were validated with QPerfect's MIMIQ emulator.
Why it matters
A key whose single use is enforced by physics rather than by trust or consensus could support delegated signing, secure token transfer and publicly verifiable randomness, the applications the authors list. QCR notes that holding the quantum key until it is used favours hardware with long coherence times, such as neutral-atom processors.
What to watch
The authors are explicit that these are pre-obfuscation counts: a secure version still needs modified key generation and a security proof for the obfuscated construction. QCR adds that fully protecting key generation against adversarial manipulation of input states will depend on future advances in quantum obfuscation. The required logical qubit counts also put practical deployment beyond today's hardware.
Sources
Facts on this page come from the sources below, retrieved by DesignQuantum.
- A quantum algorithm for one-shot signatures (arXiv:2606.23612) arxiv.org
- The quantum signing key that self-destructs (QPerfect) qperfect.io
- BTQ Technologies and QPerfect Deliver First Circuit-Level Implementation of Quantum One-Shot Signatures (Quantum Computing Report) quantumcomputingreport.com
- BTQ | Building Trusted Quantum btq.com