ringct: txn fee stuff
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4 changed files with 85 additions and 13 deletions
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@ -334,7 +334,7 @@ namespace rct {
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// this shows that sum inputs = sum outputs
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//Ver:
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// verifies the above sig is created corretly
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mgSig proveRctMG(const ctkeyM & pubs, const ctkeyV & inSk, const ctkeyV &outSk, const ctkeyV & outPk, unsigned int index) {
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mgSig proveRctMG(const ctkeyM & pubs, const ctkeyV & inSk, const ctkeyV &outSk, const ctkeyV & outPk, unsigned int index, key txnFeeKey) {
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mgSig mg;
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//setup vars
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size_t cols = pubs.size();
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@ -372,6 +372,8 @@ namespace rct {
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for (size_t j = 0; j < outPk.size(); j++) {
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subKeys(M[i][rows], M[i][rows], outPk[j].mask); //subtract output Ci's in last row
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}
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//subtract txn fee output in last row
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subKeys(M[i][rows], M[i][rows], txnFeeKey);
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}
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for (size_t j = 0; j < outPk.size(); j++) {
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sc_sub(sk[rows].bytes, sk[rows].bytes, outSk[j].mask.bytes); //subtract output masks in last row..
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@ -389,7 +391,7 @@ namespace rct {
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// this shows that sum inputs = sum outputs
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//Ver:
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// verifies the above sig is created corretly
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bool verRctMG(mgSig mg, const ctkeyM & pubs, const ctkeyV & outPk) {
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bool verRctMG(mgSig mg, const ctkeyM & pubs, const ctkeyV & outPk, key txnFeeKey) {
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//setup vars
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size_t cols = pubs.size();
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CHECK_AND_ASSERT_THROW_MES(cols >= 1, "Empty pubs");
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@ -410,20 +412,20 @@ namespace rct {
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for (j = 0; j < rows; j++) {
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for (i = 0; i < cols; i++) {
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M[i][j] = pubs[i][j].dest;
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addKeys(M[i][rows], M[i][rows], pubs[i][j].mask);
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addKeys(M[i][rows], M[i][rows], pubs[i][j].mask); //add Ci in last row
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}
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}
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for (size_t j = 0; j < outPk.size(); j++) {
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for (i = 0; i < cols; i++) {
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subKeys(M[i][rows], M[i][rows], outPk[j].mask);
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for (j = 0; j < outPk.size(); j++) {
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subKeys(M[i][rows], M[i][rows], outPk[j].mask); //subtract output Ci's in last row
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}
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//subtract txn fee output in last row
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subKeys(M[i][rows], M[i][rows], txnFeeKey);
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}
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key message = cn_fast_hash(outPk);
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DP("message:");
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DP(message);
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return MLSAG_Ver(message, M, mg);
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}
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//These functions get keys from blockchain
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@ -466,6 +468,8 @@ namespace rct {
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//decodeRct: (c.f. http://eprint.iacr.org/2015/1098 section 5.1.1)
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// uses the attached ecdh info to find the amounts represented by each output commitment
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// must know the destination private key to find the correct amount, else will return a random number
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// Note: For txn fees, the last index in the amounts vector should contain that
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// Thus the amounts vector will be "one" longer than the destinations vectort
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rctSig genRct(const ctkeyV & inSk, const keyV & destinations, const vector<xmr_amount> amounts, const ctkeyM &mixRing, unsigned int index) {
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CHECK_AND_ASSERT_THROW_MES(amounts.size() > 0, "Amounts must not be empty");
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CHECK_AND_ASSERT_THROW_MES(amounts.size() == destinations.size(), "Different number of amounts/destinations");
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@ -498,9 +502,12 @@ namespace rct {
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}
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//set txn fee
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rv.txnFee = amounts[destinations.size()];
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key txnFeeKey = scalarmultH(d2h(rv.txnFee));
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rv.mixRing = mixRing;
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rv.MG = proveRctMG(rv.mixRing, inSk, outSk, rv.outPk, index);
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if (!verRctMG(rv.MG, rv.mixRing, rv.outPk)) { printf("proveRctMG genreated bad data\n"); }
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rv.MG = proveRctMG(rv.mixRing, inSk, outSk, rv.outPk, index, txnFeeKey);
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return rv;
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}
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@ -534,7 +541,9 @@ namespace rct {
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DP(tmp);
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rvb = (rvb && tmp);
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}
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bool mgVerd = verRctMG(rv.MG, rv.mixRing, rv.outPk);
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//compute txn fee
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key txnFeeKey = scalarmultH(d2h(rv.txnFee));
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bool mgVerd = verRctMG(rv.MG, rv.mixRing, rv.outPk, txnFeeKey);
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DP("mg sig verified?");
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DP(mgVerd);
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@ -112,8 +112,8 @@ namespace rct {
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// this shows that sum inputs = sum outputs
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//Ver:
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// verifies the above sig is created corretly
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mgSig proveRctMG(const ctkeyM & pubs, const ctkeyV & inSk, const keyV &outMasks, const ctkeyV & outPk, unsigned int index);
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bool verRctMG(mgSig mg, const ctkeyM & pubs, const ctkeyV & outPk);
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mgSig proveRctMG(const ctkeyM & pubs, const ctkeyV & inSk, const keyV &outMasks, const ctkeyV & outPk, unsigned int index, key txnFee);
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bool verRctMG(mgSig mg, const ctkeyM & pubs, const ctkeyV & outPk, key txnFee);
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//These functions get keys from blockchain
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//replace these when connecting blockchain
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@ -177,6 +177,7 @@ namespace rct {
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//pairs that you mix with
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vector<ecdhTuple> ecdhInfo;
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ctkeyV outPk;
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xmr_amount txnFee;
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BEGIN_SERIALIZE_OBJECT()
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FIELD(rangeSigs)
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@ -184,6 +185,7 @@ namespace rct {
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FIELD(mixRing)
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FIELD(ecdhInfo)
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FIELD(outPk)
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FIELD(txnFee)
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END_SERIALIZE()
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};
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@ -213,6 +213,67 @@ TEST(ringct, range_proofs)
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ASSERT_TRUE(decodeRct(s, Sk, 1));
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}
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TEST(ringct, range_proofs_with_fee)
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{
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//Ring CT Stuff
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//ct range proofs
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ctkeyV sc, pc;
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ctkey sctmp, pctmp;
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//add fake input 5000
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tie(sctmp, pctmp) = ctskpkGen(6001);
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sc.push_back(sctmp);
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pc.push_back(pctmp);
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tie(sctmp, pctmp) = ctskpkGen(7000);
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sc.push_back(sctmp);
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pc.push_back(pctmp);
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vector<xmr_amount >amounts;
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//add output 500
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amounts.push_back(500);
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keyV destinations;
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key Sk, Pk;
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skpkGen(Sk, Pk);
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destinations.push_back(Pk);
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//add txn fee for 1
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//has no corresponding destination..
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amounts.push_back(1);
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//add output for 12500
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amounts.push_back(12500);
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skpkGen(Sk, Pk);
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destinations.push_back(Pk);
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//compute rct data with mixin 500
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rctSig s = genRct(sc, pc, destinations, amounts, 3);
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//verify rct data
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ASSERT_TRUE(verRct(s));
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//decode received amount
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ASSERT_TRUE(decodeRct(s, Sk, 1));
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// Ring CT with failing MG sig part should not verify!
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// Since sum of inputs != outputs
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amounts[1] = 12501;
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skpkGen(Sk, Pk);
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destinations[1] = Pk;
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//compute rct data with mixin 500
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s = genRct(sc, pc, destinations, amounts, 3);
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//verify rct data
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ASSERT_FALSE(verRct(s));
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//decode received amount
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ASSERT_TRUE(decodeRct(s, Sk, 1));
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}
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static bool range_proof_test(bool expected_valid,
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int n_inputs, const uint64_t input_amounts[], int n_outputs, const uint64_t output_amounts[])
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{
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