Probably a simple question, but I believe it is important to state it clearly for the beginners like me out there.
What is the hash function used for the Bitcoin proof-of-work? What implementations are available? Any Java implementation?
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1Related: bitcoin.stackexchange.com/questions/6037/…– morsecoderSep 3, 2015 at 14:25
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1Related: bitcoin.stackexchange.com/questions/4317/…– morsecoderSep 3, 2015 at 14:27
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2 Answers
Bitcoin uses SHA256d to hash block headers, which is sha256(sha256(x)).
In anticipation of your next question, it uses a double hash to protect against length extension attacks (source).
answered Sep 3, 2015 at 14:30
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1In reality extension attacks aren't really applicable to proof of work anyway, but convention is probably as good of a reason as any I suppose.– ClarisSep 3, 2015 at 21:47
From Bitcoin Wiki PoW and tangentially, HashCash:
SHA256(SHA256(Block_Header)) but you have to be careful about byte-order.
Specifically, it is SHA256d
Implementations are often standard libraries, like Python's hashlib.
answered Sep 3, 2015 at 14:30
