AFAIK there are 3 hash functions to choose from in solidity (sha3, sha256, and ripemd). sha3 is native while the others use precompiled contracts.
Which one of these is cheapest (in terms of gas)?
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Your questions is slightly ambiguous. You could improve your question by specifying what you mean with "cheap". I assume you mean "which hashing algorithm has the lowest gas cost?" (Cheap can also mean in terms of computational power).– Jeffrey W.Commented Apr 20, 2016 at 7:58
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@JeffreyW. done– Akhil FCommented Apr 20, 2016 at 12:31
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1 Answer
keccak256 (new alias for sha3) is cheapest.
Source: Yellow Paper
Appendix G mentions the gas cost of sha3 is:
- 30 gas + 6 gas for each word (rounded up) for input data to a SHA3 Keccak-256 operation.
Appendix E has the costs for the others.
sha256 (SHA2-256) costs:
- 60 gas + 12 gas for each word (rounded up) for input data to a SHA2-256 operation.
ripemd is even more expensive:
- 600 gas + 120 gas for each word (rounded up) for input data to a RIPEMD-160 operation.
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2It's worth noting that calls to the
sha3built-in function (as opposed to the assembly directive) currently appear to create a contract invocation in Solidity, which is much more expensive than it needs to be. Commented Apr 20, 2016 at 9:52 -
@NickJohnson Sounds like a good question to ask if it is invoking a contract. (I kept my answer to the Yellow Paper, since values in an empirical, implementation dependent answer could change over time.)– eth ♦Commented Apr 21, 2016 at 10:33
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@NickJohnson how do we know how we're calling it? is it the difference between
blah = sha3(blah blah)andassembly { blah = sha3(blahblahblah) }?– bekahCommented Nov 28, 2016 at 10:19 -
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1@TharinduMadushanka Do you mean ethereum.stackexchange.com/questions/550/… ?– eth ♦Commented Jul 30, 2021 at 0:07