Sigbash

What is Sigbash?

Sigbash is a programmable signing primitive for Bitcoin. It lets you embed policy-bound key authorization — approval workflows, vendor whitelists, velocity limits, inheritance paths, multi-party quorums — directly into your existing Bitcoin stack. Policy enforcement is gated by a zero-knowledge proof: we cryptographically verify that your rules were satisfied without ever seeing the rules or the transaction.

How does it work?

Our system uses zero-knowledge cryptography to separate policy enforcement from policy knowledge: Policy Definition: Define spending policies using our policy builder. Policy Generation: We convert policies to a Policy Operand Expression Tree (POET), a custom data structure meant to efficiently describe signing policies.

How do I use Sigbash?

There are two ways to use Sigbash: Webapp (sigbash.com): Free, hosted, runs entirely in your browser. Define a policy in our builder, get a co-signing key protected by a passkey and PIN, import that key into any Bitcoin wallet (Sparrow, Electrum, BlueWallet, etc.), and fund it normally.

What is a POET?

POET stands for Policy Operand Expression Tree. It's the data structure we use to efficiently describe complex signing policies. It's a boolean logic tree: each leaf represents a specific constraint about the transaction (spending limits, allowed recipients, time windows), and each branch represents how those constraints combine using logical operators like AND, OR, and NOT.

What operators and conditions are supported in a POET?

POET v1.1 supports fourteen logical operators for combining conditions: AND, OR, NOT, XOR, NAND, NOR, THRESHOLD, EXACTLY, AT_MOST, IMPLIES, IFF, VETO, WEIGHTED_THRESHOLD, and MAJORITY. These let you express everything from simple "require all three conditions" logic to sophisticated weighted voting schemes. For conditions themselves, we support comprehensive Bitcoin transaction introspection across four categories.