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/* Copyright 2018 0KIMS association.
This file is part of circom (Zero Knowledge Circuit Compiler).
circom is a free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
circom is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with circom. If not, see <https://www.gnu.org/licenses/>.*/
/***************************************************************************************************Each level on a SMTProcessor has a state.
The state of the level depends on the state of te botom level and on `xor` and`is0` signals.
`isOldLev` 1 when is the level where oldLeaf is.
`xor` signal is 0 if the index bit at the current level is the same in the oldand the new index, and 1 if it is different.
`is0` signal, is 1 if we are inserting/deleting in an empty leaf and 0 if weare inserting/deleting in a leaf that contains an element.
The states are:
top: While the index bits of the old and new insex in the top level is the same, whe are in the top state.old0: When the we reach insert level, we go to old0 stateif `is0`=1.btn: Once in insert level and `is0` =0 we go to btn or new1 level if xor=1new1: This level is reached when xor=1. Here is where we insert/delete the hash of theold and the new trees with just one element.na: Not appliable. After processing it, we go to the na level.
Fnctionfnc[0] fnc[1]0 0 NOP0 1 UPDATE1 0 INSERT1 1 DELETE
########### # # ┌────────────────────────────▶# upd #─────────────────────┐ │ ## ## │ │ ######### │ levIns=1 │ │ fnc[0]=0 │ │ any │ │ │ │ │ │ │ ########### │ │ levIns=1 # # │ levIns=0 │ is0=1 ┌────────────▶# old0 #────────┐ │ any ┌─────┐ │ fnc[0]=1│ ## ## │ │ ┌──────┐ │ │ │ │ ######### │ any │ │ │ │ ▼ │ │ │ ▼ ▼ │ │ ########### │ │ ########### │ │ # # ────────────┘ └────────▶# #│ └──# top # # na # ## ## ───────────────────┐ levIns=1 ┌──▶## ## ######### │ is0=0 │ ######### │ │ fnc[0]=1 │ │ │ xor=1 ########### │ any │ └──────────────────▶# # │ │ # new1 #──┘ │ ## ## └────────────────────────────────┐ ######### levIns=1 │ ▲ is0=0 │ ┌─────┘ fnc[0]=1 │ ###########│ xor=1 xor=0 │ # # ▼# btn # ## ## #########◀───────┐ │ │ │ │ └────────────┘ xor=0
***************************************************************************************************/
template SMTProcessorSM() { signal input xor; signal input is0; signal input levIns; signal input fnc[2];
signal input prev_top; signal input prev_old0; signal input prev_bot; signal input prev_new1; signal input prev_na; signal input prev_upd;
signal output st_top; signal output st_old0; signal output st_bot; signal output st_new1; signal output st_na; signal output st_upd;
signal aux1; signal aux2;
aux1 <== prev_top * levIns; aux2 <== aux1*fnc[0]; // prev_top * levIns * fnc[0]
// st_top = prev_top*(1-levIns) // = + prev_top // - prev_top * levIns = aux1
st_top <== prev_top - aux1;
// st_old0 = prev_top * levIns * is0 * fnc[0] // = + prev_top * levIns * is0 * fnc[0] = aux2 * is0
st_old0 <== aux2 * is0; // prev_top * levIns * is0 * fnc[0]
// st_new1 = prev_top * levIns * (1-is0)*fnc[0] * xor + prev_bot*xor = // = + prev_top * levIns * fnc[0] * xor = aux2 * xor // - prev_top * levIns * is0 * fnc[0] * xor = st_old0 * xor // + prev_bot * xor = prev_bot * xor
st_new1 <== (aux2 - st_old0 + prev_bot)*xor;
// st_bot = prev_top * levIns * (1-is0)*fnc[0] * (1-xor) + prev_bot*(1-xor); // = + prev_top * levIns * fnc[0] // - prev_top * levIns * is0 * fnc[0] // - prev_top * levIns * fnc[0] * xor // + prev_top * levIns * is0 * fnc[0] * xor // + prev_bot // - prev_bot * xor
st_bot <== (1-xor) * (aux2 - st_old0 + prev_bot)
// st_upd = prev_top * (1-fnc[0]) *levIns; // = + prev_top * levIns // - prev_top * levIns * fnc[0]
st_upd <== aux1 - aux2
// st_na = prev_new1 + prev_old0 + prev_na + prev_upd; // = + prev_new1 // + prev_old0 // + prev_na // + prev_upd
st_na <== prev_new1 + prev_old0 + prev_na + prev_upd;
}
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