# SIGHASH_ANYPREVOUT (BIP118) (formerly `SIGHASH_NOINPUT`) - Good informative page describing all the features it enables: http://anyprevout.xyz/ - Page in [[Bitcoin Optech]]: https://bitcoinops.org/en/topics/sighash_noinput/ - Bip 118: https://github.com/bitcoin/bips/blob/master/bip-0118.mediawiki - Enables [[PTLC|PTLCs]] ## anyprevout.xyz ### Enables [[eltoo]] Bringing all the benefits of eltoo, as well as: - Lightweight and almost free watchtowers. - [[Lot 49]] for Lightning-powered low-latency mesh networks. ### Enables [[Covenants]] Covenants are a way to make sure one transaction can only be spent by an specific other can be achieved using [this secret little trick](https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2019-June/017036.html) that embeds the signature for transaction `t+1` right inside the output of transaction `t`. #### [[Covenants]] => [[Spacechains]] ![[Spacechains]] With [[Spacechains]] we can do - A chain for all kinds of assets issued by entities or individuals; - A DNS chain that solves Zooko's triangle without needing an altcoin; - A chain that executes Ethereum-like smart-contracts; - A chain with BTC IOU tokens in it, guaranteed by an entity, by hashrate escrows, some magical zero-knowledge proof system or some other complex mechanism yet to be invented; - A chain with all of the above;All without burdening Bitcoin users and at the same time paying fees to miners who don't even have to be aware these things exist. #### Additional benefits of [[Covenants]] 1. Safer [[Bitcoin Vaults]] 2. Replaces and improves the convoluted [BIP301](https://bips.xyz/301) with a native, simple blind merged-mining scheme that requires zero setup or new software from mining nodes.