better error messages for invalid input circuits

[amaloz]

Inputting a circuit (versus a formula) gives the following error:

networkx.exception.NetworkXError: ('The node sets of G and H are not disjoint.', 'Use appropriate rename=(Gprefix,Hprefix)or use disjoint_union(G,H).')

It should be a error message saying the input must be a formula.

[crypto-aretuza]

I got this error when I was trying to obfuscate .circ file with 7 inputs (in default construction) and I used the gate:

gate XOR 0 6

I guess it was because in agis_bp.py line 193 you set:

tmpidx = len(bp1.graph) + len(bp2.graph)

It actually isn't outside of the range of possible indices. In my example this two graphs are of length 3 (because it is xor of two inputs) so tmpidx=6 and in union of graphs I got the collision with my input 6. I fixed it by adding big number to tmpidx, but maybe it should be done by passing number of inputs to _xor_gate() as parameter

[amaloz]

Could you send me the example .circ file? I'm phasing out AGIS from the codebase (since SZ is a better approach) so I want to make sure this is still reproducable when using SZ.

[crypto-aretuza]

It works good in SZ

: nins 7
: depth 5
# TEST 1111010 0
0 input
1 input
2 input
3 input
4 input
5 input
6 input
7 gate AND 1 2
8 gate AND 7 3  
9 gate AND 8 4 
10 gate AND 9 5
11 gate XOR 0 6
12 output AND 11 10

[amaloz]

Once #34 is taken care of, this'll no longer be relevant.