CIP: Integration of keccak256 into Plutus.

CIP-0382/README.md

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+---
+CIP: 382
+Title: Integration of `keccak256` into Plutus 
+Authors: Sergei Patrikeev <[email protected]>
+Discussions-To: https://github.com/cardano-foundation/CIPs/pull/524
+Comments-URI: https://github.com/cardano-foundation/CIPs/pull/524
+Status: Draft
+Category: Plutus
+Type: Standards Track
+Created: 2023-06-13
+Post-History: None 
+License: Apache-2.0
+---
+
+## Abstract
+This CIP proposes an extension of the current Plutus functions to provide support for the [`keccak256`](https://keccak.team/files/Keccak-submission-3.pdf) hashing algorithm,
+primarily to ensure compatibility with Ethereum's cryptographic infrastructure.
+
+## Motivation
+
+The [integration](https://github.com/input-output-hk/cardano-base/pull/252) of the ECDSA and Schnorr signatures over the secp256k1 curve into Plutus was a significant 
+step towards interoperability with Ethereum and Bitcoin ecosystems. However, full compatibility is still impossible 
+due to the absence of the `keccak256` hashing algorithm in Plutus interpreter, 
+which is a fundamental component of Ethereum's cryptographic framework:
+- data signing standard [EIP-712](https://eips.ethereum.org/EIPS/eip-712), 
+- `keccak256` is the hashing algorithm underlying Ethereum's ECDSA signatures. 
+- EVM heavily [depends](https://ethereum.github.io/yellowpaper/paper.pdf) on `keccak256` for internal state management
+
+Adding `keccak256` to Plutus would enhance the potential for cross-chain solutions between Cardano and EVM-based blockchains.
+
+## Specification
+`keccak256` function is already available in [cardano-base](https://github.com/input-output-hk/cardano-base/blob/master/cardano-crypto-class/src/Cardano/Crypto/Hash/Keccak256.hs).
+The changes would require a single function to be added to Plutus.
+
+## Rationale
+While the `keccak256` function might be implemented in on-chain scripts, doing so would be computationally unfeasible. 
+
+## Path to Proposed
+To move this Draft to Proposed, we need to cost the `keccak256` function.
+
+### Trustworthiness of Implementations
+The implementation of `keccak256` is based on the version found in the [cardano-base](https://github.com/input-output-hk/cardano-base/blob/master/cardano-crypto-class/src/Cardano/Crypto/Hash/Keccak256.hs) library.
+
+### Costing of function
+We performed some benchmarks (2,7 GHz Quad-Core Intel Core i7) on the `keccak256` that can be used to finalize the costing:
+* Empty Input:
+  * `keccak256("")` -> N ms  
+* Short Fixed-Length Inputs (1, 2, 4, 8, 16, 32)
+  * `keccak256("a" ^ 1)` -> N ms
+  * `keccak256("a" ^ 2)` -> N ms
+  * `keccak256("a" ^ 4)` -> N ms
+  * `keccak256("a" ^ 8)` -> N ms
+  * `keccak256("a" ^ 16)` -> N ms
+  * `keccak256("a" ^ 32)` -> N ms
+* Long Fixed-Length Inputs (256, 512, 1024) 
+  * `keccak256("a" ^ 256)` -> N ms
+  * `keccak256("a" ^ 512)` -> N ms
+  * `keccak256("a" ^ 1024)` -> N ms
+* Recursive hashing
+  * `keccak256(keccak256("a"))` -> N ms
+  * `keccak256(keccak256(keccak256("a")))` -> N ms
+
+## Backward Compatibility
+The addition of `keccak256` is backward compatible and will not interfere with existing functions within Plutus.
+
+## Path to Active
+Upon successful review and evaluation, the `keccak256` function is planned for release in an upcoming update.
+
+## References
+- keccak256: https://keccak.team/files/Keccak-submission-3.pdf
+- Ethereum Yellow Paper: https://ethereum.github.io/yellowpaper/paper.pdf
+- Ethereum standard on signing data: https://eips.ethereum.org/EIPS/eip-712