Change hash function for support in Plutus #2766
Description
Context & versions
The current recursion circuit uses Poseidon hash to generate efficiently the challenges in circuit. However this hash function is not supported on Plutus and there is no short term plan too (as there is no one standard instantiation of it).
We thus need to change the hash function to one supported by Plutus.
Potential ideas include:
- changing directly the hash to sha2/blake2
- wrappring the recursion in a circuit using sha2/blake2