107 lines
2.7 KiB
Plaintext
107 lines
2.7 KiB
Plaintext
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pragma circom 2.0.0;
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include "../circomlib/circuits/smt/smtprocessor.circom";
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include "../circomlib/circuits/smt/smtverifier.circom";
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include "../circomlib/circuits/comparators.circom";
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// input:
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// oldRoot
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// from
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// amount
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// to
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// signature
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// extra input:
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// fromBalance
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// toBalance
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// fromSiblings
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// toSiblings
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// output:
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// newRoot
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//
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// proves:
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// signature is verified
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// from balance >= amount
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// oldRoot calculated
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//
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// limited by sparse merkle tree implementation,
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// we can't directly change the tree at once
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// we can only update the tree with each leaf changes
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// so we have an intermediate root showing from balance is reduced
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//
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// for each merkle tree proof, a list of siblings is required
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// and provided as inputs
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//
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// original balance must be provided to calculate the new balance
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//
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// assumptions:
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// - from and to is in tree
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template AccountChange(nlevels) {
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signal input from;
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signal input amount;
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signal input to;
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signal input oldRoot;
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signal input signature;
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signal input fromBalance;
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signal input fromSiblings[nlevels];
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signal input toBalance;
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signal input toSiblings[nlevels];
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signal output newRoot;
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// verify signature
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// verify user's balance
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component BalanceCheck = SMTVerifier(nlevels);
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BalanceCheck.enabled <== 1;
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BalanceCheck.root <== oldRoot;
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for (var i = 0; i < nlevels; i++)
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BalanceCheck.siblings[i] <== fromSiblings[i];
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BalanceCheck.oldKey <== from;
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BalanceCheck.oldValue <== fromBalance;
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BalanceCheck.isOld0 <== 0;
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BalanceCheck.key <== from;
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BalanceCheck.value <== fromBalance;
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BalanceCheck.fnc <== 0;
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// abort if balance is not enough
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component EnoughMoney = GreaterThan(252);
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EnoughMoney.in[0] <== fromBalance;
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EnoughMoney.in[1] <== amount;
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EnoughMoney.out === 1;
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// update from's balance
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component ReduceFrom = SMTProcessor(nlevels);
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ReduceFrom.oldRoot <== oldRoot;
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for (var i = 0; i < nlevels; i++)
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ReduceFrom.siblings[i] <== fromSiblings[i];
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ReduceFrom.oldKey <== from;
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ReduceFrom.oldValue <== fromBalance;
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ReduceFrom.isOld0 <== 0;
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ReduceFrom.newKey <== from;
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ReduceFrom.newValue <== fromBalance - amount;
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ReduceFrom.fnc[0] <== 0;
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ReduceFrom.fnc[1] <== 1;
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// update to's balance
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component IncreaseTo = SMTProcessor(nlevels);
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IncreaseTo.oldRoot <== ReduceFrom.newRoot;
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for (var i = 0; i < nlevels; i++)
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IncreaseTo.siblings[i] <== toSiblings[i];
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IncreaseTo.oldKey <== to;
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IncreaseTo.oldValue <== toBalance;
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IncreaseTo.isOld0 <== 0;
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IncreaseTo.newKey <== to;
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IncreaseTo.newValue <== toBalance + amount;
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IncreaseTo.fnc[0] <== 0;
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IncreaseTo.fnc[1] <== 1;
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// output the new root
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newRoot <== IncreaseTo.newRoot;
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}
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component main {public [oldRoot]} = AccountChange(10);
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