Bitcoin Magazine
Bull Bitcoin Becomes First Exchange to Add Payjoin Privacy Deposits, Withdrawals, and Payjoin-by-Default Trading
Bull Bitcoin announced deep Payjoin integration with its exchange, claiming to be the first Bitcoin exchange in the world to offer Payjoin as a deposit and withdrawal option. The update unlocks two new concepts: “Payjoin-by-default and Payjoin trading,” according to he press release shared with Bitcoin Magazine.
Founded by Francis Pouliot in Canada in 2013, Bull Bitcoin is the world’s longest-running Bitcoin-only exchange. Its non-custodial platform lets customers in Canada, Europe, and Latin America buy Bitcoin directly into their own wallet and sell Bitcoin to their bank account. Bull Bitcoin also develops BULL Wallet, a free and open-source self-custodial Bitcoin wallet. The company has been self-funded since its inception.
Payjoin is a Bitcoin onchain privacy protocol that breaks basic assumptions made by on-chain analysis firms about user behaviour. One such assumption is that one of the unspect transaction outputs (UTXOs) resulting from a bitcoin transaction will be change returning to the sender. Or that amounts are more often than not denominated in dollars. Payjoin protocols add an off-chain coordination layer such that the amounts sent and returned to the sender obfuscate user intent and thus protect their privacy on-chain. Payjoin does not require a hard fork or a soft fork into Bitcoin consensus. Instead, it must be adopted by user wallets and exchanges to scale, but it also does not depend on collective action to benefit individual users. Bull Bitcoin’s Payjoin integration is closely based on the Payjoin Foundation‘s work.
Every time a BULL Wallet user buys or sells Bitcoin on-chain via their built-in exchange, that transaction will be a Payjoin by default. This will allow Bitcoin buyers to passively aggregate their wallet’s UTXOs, which can reduce their Bitcoin mining fees in the future. “Many Bitcoin users do not even know that they must periodically “merge” their coins by spending them to a new address in their Bitcoin wallet, if they want to reduce the economic costs of future Bitcoin transactions,” explained the press release. Payjoin-by-default automates this process. Not only does this help reduce the size of Bitcoin’s UTXO set, making it easier for everyone to run a Bitcoin node, but it also reduces fee pressure for every Bitcoin user.
Payjoin trading is a novel concept that protects users from malicious actors trying to gain insights into their financial habits by conducting chain analysis. Because transaction amounts in Bitcoin are public, it’s possible to reverse-engineer information such as someone’s salary or trading strategies such as dollar-cost averaging. Bull Bitcoin is a non-custodial exchange, so every trade leaves an on-chain trail.
The widespread adoption of Payjoin in the Bitcoin network makes common input ownership and change output detection heuristics less reliable. Bull Bitcoin’s Payjoin implementation reduces round numbers in the amounts sent as well as address reuse, and reduces the possibility of third-party onlookers guessing the fiat value of Bitcoin transactions. Introducing Payjoin-by-default and Payjoin trading means that the more people use Bull Bitcoin, the more privacy the Bitcoin network gains as a whole; “This is part of our philosophy to align the incentives of our company with the interests of all Bitcoin users.”
In December 2024, BULL Wallet became the world’s first Bitcoin wallet to integrate the Payjoin V2 protocol. This was a highly experimental project coordinated with Dan Gould and the Payjoin Dev Kit team, who have since founded the Payjoin Foundation.
Researchers have used the insights from this experimentation to improve the Payjoin experience to make it more seamless and resistant to attacks. The software powering Payjoin, both for the wallet and for the exchange, is fully free and open-source.
To benefit from these features, all a user has to do is download BULL Wallet, create a Bull Bitcoin exchange account, and log into their account via the BULL mobile app; “The rest happens automatically, like magic!”
This post Bull Bitcoin Becomes First Exchange to Add Payjoin Privacy Deposits, Withdrawals, and Payjoin-by-Default Trading first appeared on Bitcoin Magazine and is written by Juan Galt.
