Bitcoin and quantum computers: what Blockstream proposes, and what QuietProof is

Your bitcoin is protected by a digital signature: only the holder of the private key can sign a valid transaction. Powerful quantum computers could, in theory, break the kind of signatures Bitcoin uses today. In May 2026 Blockstream's director of research Jonas Nick wrote that "there is no concrete proposal for a post-quantum signature scheme in Bitcoin today." His team is working on one, and he presents it in Lugano.

Bitcoin already trusts one kind of cryptography very deeply: hash functions such as SHA-256, which secure mining and addresses. Signatures can be built from hash functions alone. Researchers consider this a conservative choice, because it adds no new mathematical assumptions.

The catch is size. Today's Schnorr signature is 64 bytes. The NIST-standard hash-based scheme, SLH-DSA, produces signatures of about 7.8 KB. Blockstream estimates that with signatures that big, Bitcoin could process only about 0.36 transactions per second.

Blockstream Research proposes two designs that shrink these signatures:

• SHRINCS gives one key two ways to sign. The everyday path makes signatures from 324 bytes, growing by about 16 bytes with each further signature. If the device loses its saved state, a backup path still works, with signatures of about 5.7 KB, roughly 25% smaller than SLH-DSA.
• SHRIMPS (March 2026) lets one seed backup be loaded into several signing devices, each making signatures of about 2.5 KB.

A draft BIP for SHRINCS lists six authors, including Jonas Nick. Blockstream also sketched a new script command, OP_CHECKSHRINCS, for using it in Bitcoin.

Adding a new signature type to Bitcoin needs a soft fork: a rule change that wallets, nodes and miners adopt. Today there is a draft specification and research, not an activation plan. As the recent BIP-110 episode showed, a rule change without broad support fails.

The forum says Jaromil, scientific director of the Plan ₿ Foundation, will premiere QuietProof in Lugano: a zero-knowledge proof that lets you prove you own bitcoin without revealing your key. The same post mentions Bitcoin Roots, which aims to make running your own node at home easy.

• 23 Oct, 15:30 Lugano / 16:30 MSK, UTXO Room: "BlindZap, Private Bitcoin Rights and Post-Quantum Proofs", Jaromil (masterclass, advanced level)
• 24 Oct, 15:30 / 16:30, P2P Stage: "Post-Quantum Signatures for Bitcoin", Jonas Nick (Blockstream)
• 24 Oct, 15:30 / 16:30, UTXO Room: "CISA: Aggregating Signatures For Bitcoin Transactions", Fabian Jahr (Brink). CISA would combine several signatures in a transaction into one.