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40 lines
1.5 KiB
Markdown
40 lines
1.5 KiB
Markdown
---
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title: Keccak-256 Hash Function
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---
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# Keccak-256 Hash Function
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Monero employs Keccak as a hashing function. In most context specifically Keccak-256 is used,
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providing 32-byte hashes.
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Keccak is the leading hashing function, designed by non-NSA designers.
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Keccak won [NIST competition](https://en.wikipedia.org/wiki/NIST_hash_function_competition) to become the official SHA3.
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## Use Cases
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Monero does **not** employ Keccak for Proof-of-Work. Instead, Keccak is used for:
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* random number generator
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* block hashing
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* transaction hashing
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* stealth address private key image (for double spend protection)
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* public address checksum
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* RingCT
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* multisig
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* bulletproofs
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...and likely a few other things.
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## Keccak-256 vs SHA3-256
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SHA3-256 is Keccak-256, except that NIST changed the padding.
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For this reason, the original Keccak-256 gives a different hash value than NIST SHA3-256.
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Monero uses original Keccak-256.
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The NIST standard was only published on August 2015, while Monero went live on 18 April 2014.
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## Reference
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* [Keccak source code used in Monero](https://github.com/monero-project/monero/blob/5c2dfe157b48a486eb2b92dcf8789b3b1eb20f60/src/crypto/keccak.c)
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* [SHA3 on Wikipedia](https://en.wikipedia.org/wiki/SHA-3)
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* [Keccak-256 vs SHA3-256](https://ethereum.stackexchange.com/questions/550/which-cryptographic-hash-function-does-ethereum-use) explained on Ethereum stackexchange
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* [Online tool to calculate Keccak-256 and SHA3-256](https://emn178.github.io/online-tools/keccak_256.html)
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