What is the theoretical minimum number of logical operations an ASIC needs to perform to compute double iterated SHA256, i.e., sha(sha(•))?
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Is this the best way to phrase the question? It seems like you'd want to know 1) the number of gates required to implement it, and 2) how much it can be pipelined (probably quite a lot.)– Nick ODellCommented Apr 19, 2015 at 8:33
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1 Answer
SHA256D, which is what Bitcoin uses, is 128 rounds, comprising
768 additions,
640 ORs
896 XORs
And a bunch of bit shifts but bit shifts are free on an ASIC.
(source)
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Those numbers don't seem correct. I count 522 additions across one iteration of SHA256, for example. (1044 across two) en.wikipedia.org/wiki/SHA-2#Pseudocode Commented Apr 19, 2015 at 8:32
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1...and I'm counting 600 additions for one SHA256 block: 48*3 + 64*7 + 8. Honestly I think this should be closed as off-topic and re-posted to crypto.stackexchange.com where you could attract the attention of a crypto expert. Commented Apr 19, 2015 at 15:03