A secure large-scale instant payment system based on blockchain

Off-chain payments are an important technique for improving the scalability of blockchain-based cryptocurrencies. However, since tokens locked in off-chain channels cannot circulate from one channel to another, current off-chain payment systems have a limitation in their capacities. In this work, we present a secure large-scale instant payment (SLIP) system to improve the capacity of blockchain systems. The SLIP system uses an aggregate signature scheme to connect some of the off-chain channels such that tokens locked in these channels can circulate from one channel to the next. Therefore, the amount of circulated tokens in these channels is the sum of all locked-in tokens instead of the minimum locked-in tokens. In other words, it improves the negotiability of tokens locked in these connected off-chains channels. Besides, as payers can aggregate the signatures incrementally, payees only need to verify a line of transactions once in each transaction while nodes (miners) who maintain the blockchain system only need to verify all transactions once for all, which makes the SLIP system very efficient. We prove that if the underlying blockchain system is secure, and aggregate signature satisfies aggregate chosen-key security, then the SLIP system is secure. Finally, analyses show that the capacity of the SLIP system is much larger than the Lightning Network.