Breeze Privacy Protocol at a glance:
- BTC tumbling using TumbleBit’s Classic Tumbler Mode
- Very high degree of anonymity, determined by the number of participants in each tumbling cycle
- BTC Tumbling Cycle time of 117 blocks, or roughly 19.5 hours
- BTC Tumbling fee of 1.55%, plus the standard network fee chosen by the user
The Breeze Privacy Protocol is a feature of the Breeze Wallet. It is a non-centralized, in-wallet implementation of TumbleBit. TumbleBit is a trustless, unlinkable privacy solution for Bitcoin. It uses an untrusted intermediary called a Tumbler to enhance anonymity. It is trustless because the Tumbler cannot steal BTC and cannot send BTC to itself, and it enhances anonymity by mixing k people in such a way that it cannot link any of the people involved. The Tumbler can learn nothing about the relationship between anyone involved in the tumbling process. In the Breeze Privacy Protocol implementation of TumbleBit, the Tumblers are the Stratis Masternodes which make up the Masternode server.
Tumbling is hard to perform successfully. Coordinating that many people and ensuring they follow the process correctly requires a sophisticated service. Such services exist, as do services performing other kinds of mixing (you can find a good discussion on existing mixing/tumbling processes and services in the TumbleBit whitepaper). However, these services are not the best solution. There is always a risk that any closed source third-party service will steal your BTC or simply not work. There is also a case in which the Tumbler can link parties involved: if one or both of the parties (in the tumbling Alice-Bob pair) collude with the Tumbler. If the tumbling is centralized, i.e. a third-party service providing a Tumbler, it makes it easier for collusion to be performed.
This is where the Breeze Privacy Protocol and the Breeze Wallet comes in. The Breeze Privacy Protocol is open source, so anyone who wishes to do so can audit the code to verify that it is safe and does what it says on the tin. It makes the tumbling process as easy as possible by providing the service fully in-wallet: download the wallet, follow the setup process and you can be tumbling your BTC in no time. The real kicker is that Breeze is decentralized. The tumbling itself is performed by Stratis Masternodes. When you elect to start a tumbling cycle, Breeze will broadcast the attempt to connect to the tumbling Masternode server and it will establish which Masternodes meet the requirements (denomination – how much BTC you want to tumble, elected fee, collateral, etc.) and then randomly chooses a valid Masternode to perform that tumbling cycle. This means that there cannot be collusion between the tumbling participants and the Tumbler.
Each cycle provides the participants with an anonymity set equal to the number of participants. If 99 people are tumbling with you, you’ll have an anonymity set of 100. This is beyond what is achievable with most current privacy solutions for Bitcoin and also better than other altcoin solutions (for example, Monero achieves an anonymity set of between 2 and 10).
At the moment, the Breeze Wallet is a multi-chain wallet that lets a user hold both BTC and STRAT, but only allows them to tumble BTC. Stratis Group Ltd are working on support for STRAT tumbling as well, which will have a cycle time of just 2 hours, rather than BTC’s 19.5 hours.
The Breeze Privacy Protocol is an implementation of NTumblebit, a C# implementation of of TumbleBit. As things stand, it supports the Classic Tumbler Mode of TumbleBit; however, work is being done to support the Payment Hub Mode also. The Payment Hub Mode works with just two on-chain transactions and then introduces anonymity through a series of off-chain payments (similar to the Lightning Network). This also facilitates significant scaling potential for Bitcoin itself. These are early days, but TumbleBit has what it takes to make big waves in the Bitcoin scaling debate.
The Breeze Privacy Protocol Masternodes are operated by STRAT holders and require a collateral of 250,000 STRAT as well as 5 BTC which will be used to perform the tumbling itself.
You can read in more depth about the privacy problem and the Breeze Wallet solution in this article.