Mixed cryptocurrency transactions now represent 4.09% of all bitcoin (BTC) payments, according to data published by Longhash on April 29.

So-called “CoinJoins” have risen by 300% in the space of nine months. By blending multiple transactions together before they are sent to the recipient, the technique is regarded as a way of obscuring the sender’s details.

The data was provided by Adam Fiscor, the CTO of the company that runs Wasabi Wallet, a product that aims to deliver greater levels of anonymity to bitcoin users. It shows that CoinJoin transactions have reached their highest level since 2013-14.

CoinJoins have become more popular as governments around the world begin to step up their monitoring of transactions on blockchain, with law enforcement agencies often using specialist companies such as Chainalysis to pursue hackers and criminals dealing in crypto.

Although privacy coins have been touted as an alternative to BTC, they are experiencing pushback in some countries. Officials in France have suggested they should be banned altogether, while China recently enforced new anti-anonymity regulations that are purportedly designed to contribute to the industry’s healthy development.