tBTC

tBTC is the first application of the Keep Network. It is a trust-minimized bridge between the Bitcoin and Ethereum blockchains. When a request comes to mint tBTC on Ethereum, tBTC selects a group of "signers" using its random beacon that oversees the process. Each signing group consists of three nodes selected to custody incoming BTC, which can be deposited in lots (fixed sizes like 0.1 BTC, 1 BTC, etc). Signers must first overcollateralize the incoming BTC amount by 150% of the value in ETH. The signing group then generates a Bitcoin wallet using a threshold ECDSA protocol, which users can then send their BTC to. Finally, the user generates a Simplified Payment Verification (SPV) proof of their deposit transaction and sends it to the Ethereum chain, where they receive the TBTC Deposit Token (TDT) - a non-fungible token that represents a claim to a deposit's underlying UTXO on the Bitcoin blockchain. TDT allows the user to mint tBTC.

tBTC launched on the Ethereum and Bitcoin mainnets in May 2020. But a vulnerability discovered in the code a few day post-launch led tBTC's development team, Thesis, to pause user deposits. After several rounds of security audits and retesting the app on a public testnet, the team relaunched tBTC in Sep. 2020.