TumbleBit
TumbleBit is a anonymous payments protocol from 2016 that is fully compatible with today’s Bitcoin protocol. TumbleBit allows parties to make payments through an untrusted Tumbler. No-one, not even the Tumbler, can tell which payer paid which payee during a TumbleBit epoch. TumbleBit consists of two interleaved fair-exchange protocols that prevent theft of bitcoins by cheating users or a malicious Tumbler. TumbleBit combines fast cryptographic computations (performed off the blockchain) with standard bitcoin scripting functionalities (on the blockchain) that realize smart contracts.
TumbleBit was proposed by Ethan Heilman and colleagues as an “untrusted Bitcoin-compatible anonymous payment hub.” It has three different parts. First, users and the tumbler lock coins in a 2-of-2 multisig contract so funds cannot be stolen. Following that, users solve RSA puzzles issued by the tumbler; revealing the solution proves the tumbler must pay them later, but the tumbler does not learn which customer solved which puzzle. The specific type of puzzle being solved is described in detail in the whitepaper. Finally, users redeem their puzzles for fresh outputs, and the tumbler can take its fee.
TumbleBit inspired related implementations such as NTumbleBit and Breeze Wallet.
Note that A2L is faster and uses less bandwidth than TumbleBit.[1]
External links
- https://eprint.iacr.org/2016/575 - The paper
- https://github.com/BUSEC/TumbleBit - Implementation
- https://joinmarket.me/blog/blog/tumblebit-for-the-tumble-curious/
- https://medium.com/@nopara73/tumblebit-vs-coinjoin-15e5a7d58e3
- https://www.youtube.com/watch?v=8BLWUUPfh2Q&t=3787 - Talk at ScalingBitcoin 2016
- https://diyhpl.us/wiki/transcripts/scalingbitcoin/milan/tumblebit/ - Transcript of talk