Clear DefinitionsThreshold Bridge
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Pronunciation
[thresh-ohld brij]
Analogy
A threshold bridge is like requiring a quorum of bank managers to sign a wire transfer before it executes.
Definition
A cross-chain bridge that secures asset transfers using threshold cryptography, requiring a subset of key holders to jointly sign off on transactions.
Key Points Intro
Threshold bridges use multi-party signatures to protect cross-chain transfers.
Key Points
Threshold signature: k-of-n participants authorize transfers
Decentralization: no single key controls assets
Security model: tolerates up to n–k malicious signers
Performance: signature aggregation reduces on-chain footprint
Example
A bridge contract accepts BLS threshold signatures from 5 of 7 validators to mint wrapped tokens on the target chain.
Technical Deep Dive
Validators run a Distributed Key Generation (DKG) protocol to share a public key without revealing private shares. To approve a transfer, k validators compute partial BLS signatures, which are aggregated off-chain into a single compact signature that the bridge contract verifies before releasing assets.
Security Warning
If k or more colluding signers compromise their shares, they can initiate unauthorized transfers.
Caveat
Setup complexity and key-share management overhead increase operational burden.
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