The following is a collection of resources related to covenants, aggregated and maintained by Robin Linus from ZeroSync. Follow his repository for the latest version of the collection.
Covenant-enabling Bitcoin Features
BIP119: CHECKTEMPLATEVERIFY (CTV) by Jeremy RubinBIP118: SIGHASH_ANYPREVOUT (APO) (aka SIGHASH_NOINPUT) by Christian Decker and Anthony TownsOP_CAT by Andrew PoelstraOP_CHECKSIGFROMSTACK (CSFS) + OP_CATOP_TAPLEAF_UPDATE_VERIFY (TLUV) by Anthony TownsTXHASH + CHECKSIGFROMSTACKVERIFY (TXHASH + CSFS) by Russel O’ConnorOP_EVICT by ZmnSCPxj
Properties of Covenants
Granularity: Which transaction fields can be defined by the covenant?Overhead: How many bytes are required per TX?Simplicity: How complex is the implementation and the usability?Status: Is there a BIP? PR? Reviews? Signet? Testnet? Signals? Merged?Recursion: Can the covenant be applied endlessly to itself?Use cases: For which applications is the covenant the optimal solution?
Resources
CTV WebsiteAPO Websitebitcoinops.org – Covenantsbitcoinops.org – Covenant opcode proposalBitcoin Covenants (Möser et al, 2016)Enhancing Bitcoin Transactions with Covenants (O’Connor et al, 2017)Bitcoin Covenants: Three Ways to Control the Future (Swambo et al, 2020)bitcoincovenants.com – A compilation of research on Bitcoin CovenantsJeremy Rubin AMAUnhashedPodcast – Russell O’Connor’s reframing of OPs APO+CTVCoinCovenants using SCIP signatures, an amusingly bad idea. (2013)Covenants in Elements Alpha (2016)Bitcoin2022 – What Are Covenants? (Video)Eltoo with Anyprevout and TaprootCTV Telegram GroupHow to emulate SIGHASH_NOINPUT using CHECKSIGFROMSTACKVERIFY?
Comparisons to CTV
Anthony Towns: “I don’t think of TLUV as an alternative to CTV”Christian Decker: “I consider the two proposals [APO and CTV] complementary, and not competing”Alternatives to CTV
Projects based on covenants
CTV use casesSimple CTV VaultSpacechainsStakechainsCTV dramatically improves DLCsAutomated Market Maker by Bitmatrix
CTV Activation – Pros and Cons
Pros
“Covenants have been discussed for more than 6 years.””There is strong consensus that Bitcoin should support covenants.””CTV is the most conservative approach to enable covenants.””The BIP was finalized over two years ago.””The code is well tested and reviewed.””People are testing vaults and other covenants live on the CTV signet.””There are no objections against CTV on the code level.””For 5 months there has been a 5.5 BTC bug bounty program funded by community members.””Many community members support the activation of CTV.”
Cons
“The strongest technical argument against bip119 is: since we have to do some soft fork for covenants let’s activate full-featured covenants right away instead of causing multiple forks with overlapping features.””The most likely alternative seems to be TXHASH + CSFS. It combines Eltoo fans with ctv fans in a way that makes technical sense, it satisfies those who want more complex covenants going forward, the conversational well around it is less poisoned. The main downside is that it uses a few more bytes. The work that needs to be done to get it in safely can be overcome with effort.””However, nobody is working on it. There’s no BIP yet. No review. Not even remotely a PR.””The number of bitfields in TXHASH is high, so the limiting factor would be writing a large number of both tests and arguing that any possible permutation of those bitfields does not lead to some resource exhaustion attack on some inputs.””It would take years to activate it.”