BLISK: Boolean circuit Logic Integrated into the Single Key

This development overcomes the limitations faced by traditional methods like threshold/multisignatures and scripts. Threshold signatures, despite their efficiency and privacy, are limited to expressing basic cardinality and cannot handle more complex conditions. On the other hand, scripts, while more expressive, are practically limited due to their visibility and other constraints. The introduction of a Proof of Concept (PoC) framework that compiles a monotone boolean policy—integrating AND/OR logic—over users' long-term keys into a singular signature verification key is a notable advancement. This approach simplifies the on-chain component to verifying a single Schnorr signature against one key, effectively keeping the complexity of the policy off-chain. This system not only enhances privacy and security but also introduces a level of expressiveness in digital currency transactions previously unattainable with traditional mechanisms.

The framework employs established cryptographic techniques such as MuSig2 for AND gates, Elliptic Curve Diffie-Hellman (ECDH) for OR gates, and Non-Interactive Zero-Knowledge proofs for ensuring the verifiability of circuit resolutions. This setup allows for non-interactive key rotation and the continued use of existing long-term keys, offering an advantage over threshold Distributed Key Generation systems which require new key material. The ability to enforce complex policies without exposing the policy itself to external parties is a critical feature that maintains both privacy and security.

The detailed academic paper and explainer blog post provide further insights into this framework, available at https://eprint.iacr.org/2026/088.pdf and https://hackmd.io/@olkurbatov/HJm5h0JH-l, respectively. The codebase, still not ready for production use, is open for community feedback and development at https://github.com/zero-art-rs/blisk.

An aspect of the policy implementation details how specific conditions such as (and (or A B) (or C D)) can lead to four valid coalitions capable of producing a valid signature. This structure signifies a sophisticated method of representing complex conditions through a PK tree, where the verification key is not a simple aggregation of all parties but a more nuanced combination of hash and ECDH operations leading to a MuSig2 aggregation. This demonstrates the framework's capability to accommodate a wide array of transaction conditions, surpassing the limitations of previous systems.