I am trying to obtain a circuit that computes the SHA256 hash for an input message that is greater than 512 bits.
I understand how the message is to be padded (we append a 1 and then some zeroes, and then the last 64 bits contain the length of the original message and so on).
After I do the padding, I have two 512-bit blocks.
I want to use the circuit (for the compression function) that is provided here:
The first 512 wires of the circuit are the input; the last 256 wires are the output. I think I know how to use the circuit for the first block. I can simply feed my first 512-bit block into the first 512 wires of the circuit.
But I am not sure how to proceed for the second block. In particular I need to update the h0, h1, ... , h7 values but don't know how to as I cannot identify where the wires corresponding to them are in the circuit.
Any help would be much appreciated.