Under-constrained Circuit

[UIZorrot]

It seemed like this was a legacy repo, however, it may still lurk in the newest version maybe?

https://github.com/hermeznetwork/circuits/blob/master/src/lib/utils-bjj.circom

In L#12 BitsCompressed2AySign, the input signal bjjCompressed is not fully constrained.

    for (i = 0; i < 254; i++) {
        b2nAy.in[i] <== bjjCompressed[i];
    }

The bjjCompressed[254] seemed not been constrained by the loop and other statements. As a result, this bug maybe used for forged fake proof.