circomlib/circuits/smt/smtverifiersm.circom

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2018-12-15 11:00:35 +03:00
/*
Each level in the SMTVerifier has a state.
This is the state machine.
The signals are
levIns: 1 if we are in the level where the insertion should happen
xor: 1 if the bitKey of the old and new keys are different in this level
is0: Input that indicates that the oldKey is 0
fnc: 0 -> VERIFY INCLUSION
1 -> VERIFY NOT INCLUSION
err state is not a state itself. It's a lack of state.
The end of the last level will have to be `na`
levIns=0 ###########
xor=1 # #
fnc=1 ┌──────────▶# err #
│ ## ##
levIns=0 │ #########
xor=0 || fnc=0 │ any
┌────┐ │ ┌────┐
│ │ │ │ │
│ ▼ │ levIns=1 ▼ │
│ ########### │ is0=1 ########### ########### │
│ # # ───────────┘ fnc=1 # # any # # │
└──# top # ─────────────────────▶# i0 #───────────────▶# na #──┘
## ## ──────────┐ ## ## ┌───────▶## ##
########─────────────┐│ ######### │┌────────▶#########
││ levIns=1 ││
││ is0=0 ########### ││
││ fnc=1 # # any│
│└──────────▶ # iold #────────┘│
│ ## ## │
│ ######### │
│ │
│ levIns=1 ########### │
│ fnc=0 # # any
└────────────▶# inew #─────────┘
## ##
#########
*/
template SMTVerifierSM() {
signal input xor;
signal input is0;
signal input levIns;
signal input fnc;
signal input prev_top;
signal input prev_i0;
signal input prev_iold;
signal input prev_inew;
signal input prev_na;
signal output st_top;
signal output st_i0;
signal output st_iold;
signal output st_inew;
signal output st_na;
signal prev_top_lev_ins;
signal prev_top_lev_ins_fnc;
signal xor_fnc;
prev_top_lev_ins <== prev_top * levIns;
prev_top_lev_ins_fnc <== prev_top_lev_ins*fnc; // prev_top * levIns * fnc
xor_fnc <== xor*fnc;
// st_top = prev_top * (1-levIns) * (1 - xor*fnc)
// = + prev_top
// - prev_top * levIns
// - prev_top * xor * fnc
// + prev_top * levIns * xor * fnc
st_top <== (prev_top - prev_top_lev_ins)*(1-xor_fnc);
// st_inew = prev_top * levIns * (1-fnc)
// = + prev_top * levIns
// - prev_top * levIns * fnc
st_inew <== prev_top_lev_ins - prev_top_lev_ins_fnc;
// st_iold = prev_top * levIns * (1-is0)*fnc
// = + prev_top * levIns * fnc
// - prev_top * levIns * fnc * is0
st_iold <== prev_top_lev_ins_fnc * (1 - is0);
// st_i0 = prev_top * levIns * is0
// = + prev_top * levIns * is0
st_i0 <== prev_top_lev_ins * is0;
st_na <== prev_na + prev_inew + prev_iold + prev_i0;
}