Bitcoin avoids quantum attacks without changing its code

StarkWare has just dropped a bombshell. On April 9, Avihu Levy published a proposal that could save Bitcoin from quantum computers without altering the core protocol.

The concept is called Quantum Safe Bitcoin (QSB). Essentially, it replaces Bitcoin’s current vulnerability—the ECDSA signatures on the secp256k1 curve—with something more robust. A powerful quantum computer can crack this system using Shor’s algorithm by solving discrete logarithms. Not cool. QSB says: “Let’s rely on hash functions instead.” Instead of trusting elliptic curves, the system uses the pre-image resistance of hashes. Harder to break, even for quantum machines.

How does it work exactly?

At the heart of QSB is a rather clever “hash-to-signature” puzzle. The system hashes a public key derived from the transaction with RIPEMD-160. It treats the result as a potential ECDSA signature. Like a proof-of-work challenge with a success probability of about one in 70.4 billion billion. Not easy.

Security Against Quantum Attacks

By relying on hashes rather than elliptic curves, QSB withstands Shor’s algorithm. An attacker with a quantum computer only gains a quadratic speedup with Grover’s algorithm. The security margin remains significant. Levy estimates a pre-image resistance of 118 bits under quantum threat. Solid.

The brilliant part? QSB operates within Bitcoin’s existing script limits. No need for soft forks or consensus changes. But beware: QSB transactions exceed standard relay limits. They must be submitted directly to miners.

The process unfolds in three steps: pinning phase, two rounds of digest, then transaction assembly. Not yet complete—some pipeline parts haven’t been demonstrated on-chain. But it opens a path to adapting Bitcoin to the quantum era without breaking the protocol. Market observers have noted parallels with MarketVector teaming with Coinbase to launch in recent weeks.

Costs and Practical Feasibility

Generating a valid QSB transaction costs between $75 and $150 with cloud GPUs. Levy finds this reasonable. These costs can be spread across multiple machines, making the process accessible to those with adequate computing resources.

Preliminary tests show that puzzle solutions can be found in a few hours with multiple GPUs. Complex, but feasible with current infrastructure. No need to wait decades.

Levy notes that QSB maintains compatibility with Bitcoin’s current structure. Transactions using QSB can be integrated without complicated community approval. It avoids the heated debates that often accompany soft fork proposals.

The approach requires no new hardware or software technologies. It relies on already established cryptographic principles. This reassures users and developers concerned about the security implications of integrating unproven technologies.

QSB operates within Bitcoin’s existing script limits, notably with a 201 opcode limit per script. Transactions do not require deep code modifications. This simplifies adoption by miners and network nodes. This evolution aligns with Bitcoin Golden Cross Triggers, highlighting broader trends.

Despite promising advances, some voices in the Bitcoin community remain cautious. The lack of a complete demonstration on the blockchain raises questions. Some experts call for more rigorous tests to validate the proposed system’s effectiveness and security. Script generation tools are completed, but full assembly and dissemination have yet to be demonstrated on the blockchain.