Run ecdsa proof with groth16 on phone

[0xturboblitz]

Some work done on branch ecdsa-proof-in-app.
I get an EXC_BAD_ACCESS error. Not sure if this is because the RAM usage is too high, or if the .dat file is too large, or something else.

[demonsh]

@0xturboblitz if the error from rapidsnark you should use different function for proof generation. The problem is in the small buffer size for the key.
Replace groth16_prover with groth16ProveWithZKeyFilePath .