Set of questions to start using it

[nicola]

Hello awesome to read your paper, here a few questions:

• How do I use this? (does SCAPI plug into libsnark?)
• How was this generated? Will you make the original implementation available?

[matteocam]

Hi.
To your questions:

• If you want to use it with libsnark, I am not aware whether it is directly pluggable as it is. The TBCS format of libsnark (their boolean circuit representation basically) may not be compatible with the SCAPI one. I couldn't easily find that out googling around unfortunately. A good place to start to find out should be this one. However, if you want to use SHA256 with libsnark you may not need the type of optimizations we use in this circuit. In that case, you could for example use the implementation of SHA256 in the R1CS format (another representation libsnark uses for circuits). This is already included in libsnark and you can find an example of how to use it here: look for "sha256_compression_function_gadget".
  If you want to use it with SCAPI you can use it directly. You may find an example here. The circuits that example uses are slightly different (SHA is only a part of it), but the gist of it is the same.
• The code for the circuit generation should be available in a few weeks. Unfortunately neither me or my coauthor have the time to make it "nice enough" at the moment and get it public. I took note of it and will do that as soon as I can. If in, say, six weeks, you don't hear from me you are (really) welcome to poke me and remind me. The generation process simply uses some common sense optimization to minimize the number of AND gates.

Hope this helps! :-)
M.

[themighty1]

@matteocam , thanks again for this circuit. Is there any chance to see the circuit generation algorithm\implementation? I need to extend this circuit to hash more than 32bytes of data at a time.
Thank you for your work.