MPC Key Derivation Verification for Cryptocurrency Security
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Solution Overview
Problem
In cryptocurrency systems using threshold ECDSA signatures, there is no mechanism to prevent malicious parties from inputting incorrect shares during key derivation, leading to permanent loss of private keys and associated cryptocurrencies if key shares are lost.
Innovation Solution
A system comprising multiple computerized nodes that perform multi-party computation (MPC) multiple times, randomly select functions to verify key shares, and exchange cryptographic commitments to ensure the correctness of input shares, thereby reducing the probability of false inputs and ensuring the derivation of a valid key.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard MPC techniques are used for key derivation, then key shares can be distributed among multiple parties, but malicious parties can input incorrect shares without detection
Solution Approach 1:
The system performs preliminary verification by having parties commit to their key shares before the actual key derivation process. This preliminary commitment allows detection of malicious inputs before they can corrupt the final key, resolving the contradiction by adding verification capability without requiring complex real-time monitoring during the core MPC operation.
Solution Approach 2:
The system implements feedback mechanisms where parties exchange verification data and commit messages that allow others to verify the correctness of their inputs. This feedback loop enables detection of malicious behavior while maintaining the distributed nature of the system, addressing the reliability-complexity tradeoff by using lightweight verification protocols.
2Reliability
If MPC is performed multiple times with verification, then the probability of detecting false inputs increases, but the time and computational resources required increase
Solution Approach 1:
Instead of performing full verification in every single MPC execution, the system uses a probabilistic approach where verification is performed with sufficient frequency to achieve the desired security level. This partial verification strategy achieves adequate reliability without the excessive time cost of exhaustive checking in every operation.
Solution Approach 2:
The system adjusts verification parameters such as the number of verification rounds and the threshold for detecting malicious behavior. By optimizing these parameters, the system achieves an acceptable balance between detection probability and processing time, resolving the contradiction between reliability and time loss.
3Reliability
If key shares are distributed among multiple parties, then security against single point of failure is improved, but the risk of permanent key loss increases if shares are lost
Solution Approach 1:
The system takes preliminary anti-action by implementing verification mechanisms that detect and correct malicious or incorrect key shares before they can cause permanent damage. This prevents the loss of information by identifying problems early in the key derivation process, resolving the contradiction between distributed security and information loss risk.
Solution Approach 2:
The verification mechanism acts as an intermediary between the distributed key shares and the final derived key. It mediates the interaction by verifying the correctness of inputs from each party, ensuring that only valid shares contribute to the final key. This intermediary layer protects against information loss while maintaining the security benefits of distribution.
Data Source
AI summary
The subject matter discloses a system for enforcing correctness of a derivation key, comprising multiple computerized nodes, comprising a storage module configured to store a share of a key used as an input of a function generating the derivation key, a communication module configured to exchange information between the multiple computerized nodes, and a processing module configured to receiving a request to create the derivation key, performing an MPC process between the multiple computerized nodes, said MPC process is performed multiple times, in each time the MPC process comprises receiving the key shares as input, randomly selecting a function, outputting the outputs of the selected function to the multiple computerized nodes, the multiple computerized nodes lack access to the selected function, the multiple computerized nodes perform computations on the received outputs and exchange outputs of the computations to estimate correction of the key shares inputted into the MPC process.