Optimistic Fair Secure Computation
CRYPTO '00 Proceedings of the 20th Annual International Cryptology Conference on Advances in Cryptology
Wallet Databases with Observers
CRYPTO '92 Proceedings of the 12th Annual International Cryptology Conference on Advances in Cryptology
An Efficient System for Non-transferable Anonymous Credentials with Optional Anonymity Revocation
EUROCRYPT '01 Proceedings of the International Conference on the Theory and Application of Cryptographic Techniques: Advances in Cryptology
An Efficient Micropayment System Based on Probabilistic Polling
FC '97 Proceedings of the First International Conference on Financial Cryptography
Protocols for secure computations
SFCS '82 Proceedings of the 23rd Annual Symposium on Foundations of Computer Science
A practical scheme for non-interactive verifiable secret sharing
SFCS '87 Proceedings of the 28th Annual Symposium on Foundations of Computer Science
Optimistic fair exchange of digital signatures
IEEE Journal on Selected Areas in Communications
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We propose a scheme for privacy-preserving escrow of financial transactions. The objective of the scheme is to preserve privacy and anonymity of the individual user engaging in financial transactions until the cumulative amount of all transactions in a certain category, for example all transactions with a particular counterparty in any single month, reaches a pre-specified threshold. When the threshold is reached, the escrow agency automatically gains the ability to decrypt the escrows of all transactions in that category (and only that category). Our scheme employs the probabilistic polling idea of Jarecki and Odlyzko [JO97], amended by a novel robustness mechanism which makes such scheme secure for malicious parties. When submitting the escrow of a transaction, with probability that is proportional to the amount of the transaction, the user reveals a share of the key under which all his transactions are encrypted. Therefore, the fraction of shares that are known to the escrow agency is an accurate approximation of the fraction of the threshold amount that has been transacted so far. When the threshold is reached, with high probability the escrow agency possesses all the shares that it needs to reconstruct the key and open the escrows. Our main technical contribution is a novel tool of robust probabilistic information transfer, which we implement using techniques of optimistic fair 2-party computation.