What are Bitcoin covenants, and how do they work?

Various prominent Bitcoin experts, including Adam Back, Jimmy Song and Andreas Antonopoulos, have raised some concerns over the implementation of restrictive covenants, in particular with the BIP119.

In particular, Antonopoulos has voiced concerns over “recursive covenants” that the new update could convey, thereby deteriorating the network. A recursive covenant occurs when a programmer restricts a transaction, but he does it in a way that restricts another transaction after that, starting a domino effect resulting in future limitless recursive covenants.

Blacklisting and risks of censorship and confiscation

While locking up where a Bitcoin can be spent is advantageous to ensure more security, it also provides grounds for censorship, and control by governments, which would hinder the very existence of Bitcoin. Authorities could potentially force exchanges to withdraw only to covenants with some control over the coin.

While this same risk already exists, since governments can ask exchanges to send only to addresses with a taproot spend path or multi-sig controlled by them, could the implementation of covenants facilitate malicious purposes where it would make it easier for governments to enforce a sort of on-chain KYC? 

Fungibility threats

Covenants might interfere with Bitcoin’s fungibility — the ability of each Bitcoin to be identical in function and quality.

While useful for security and scalability, covenants would change the properties of specific Bitcoin units, essentially creating different types of digital currency, distinct according to what could be spent or where it could be sent. 

As a result, those who oppose the change argued that limiting how you can spend your Bitcoin would ultimately limit Bitcoin’s use as a digital currency, with inevitable consequences in its value.

There are strong opinions on covenants’ pros and cons; however, debates are healthy and necessary to improve a decentralized and leaderless network. Ultimately, the final decision will be down to the users and node operators who will download the software that better reflects their viewpoint.