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ringct: "simple" ringct variant

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Allows the fake outs to be in different positions for each ring.
For rct inputs only.
This commit is contained in:
Shen Noether
2016-07-09 19:30:28 +01:00
committed by moneromooo-monero
parent 37c895e5e3
commit 4fd01f2bee
6 changed files with 262 additions and 3 deletions
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211
src/ringct/rctSigs.cpp
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@@ -385,6 +385,33 @@ namespace rct {
}
//Ring-ct MG sigs Simple
// Simple version for when we assume only
// post rct inputs
// here pubs is a vector of (P, C) length mixin
// inSk is x, a_in corresponding to signing index
// a_out, Cout is for the output commitment
// index is the signing index..
mgSig proveRctMGSimple(const key &message, const ctkeyV & pubs, const ctkey & inSk, const key &a , const key &Cout, unsigned int index) {
mgSig mg;
//setup vars
size_t rows = 1;
size_t cols = pubs.size();
CHECK_AND_ASSERT_THROW_MES(cols >= 1, "Empty pubs");
keyV tmp(rows + 1);
keyV sk(rows + 1);
size_t i;
keyM M(cols, tmp);
for (i = 0; i < cols; i++) {
M[i][0] = pubs[i].dest;
subKeys(M[i][1], pubs[i].mask, Cout);
sk[0] = copy(inSk.dest);
sc_sub(sk[1].bytes, inSk.mask.bytes, a.bytes);
}
return MLSAG_Gen(message, M, sk, index);
}
//Ring-ct MG sigs
//Prove:
// c.f. http://eprint.iacr.org/2015/1098 section 4. definition 10.
@@ -432,6 +459,27 @@ namespace rct {
return MLSAG_Ver(message, M, mg, II);
}
//Ring-ct Simple MG sigs
//Ver:
//This does a simplified version, assuming only post Rct
//inputs
bool verRctMGSimple(const key &message, const mgSig &mg, const keyV &II, const ctkeyV & pubs, const key & C) {
//setup vars
size_t rows = 1;
size_t cols = pubs.size();
CHECK_AND_ASSERT_MES(cols >= 1, false, "Empty pubs");
keyV tmp(rows + 1);
size_t i;
keyM M(cols, tmp);
//create the matrix to mg sig
for (i = 0; i < cols; i++) {
M[i][0] = pubs[i].dest;
subKeys(M[i][1], pubs[i].mask, C);
}
//DP(C);
return MLSAG_Ver(message, M, mg, II);
}
//These functions get keys from blockchain
//replace these when connecting blockchain
//getKeyFromBlockchain grabs a key from the blockchain at "reference_index" to mix with
@@ -462,6 +510,24 @@ namespace rct {
return make_tuple(rv, index);
}
//These functions get keys from blockchain
//replace these when connecting blockchain
//getKeyFromBlockchain grabs a key from the blockchain at "reference_index" to mix with
//populateFromBlockchain creates a keymatrix with "mixin" columns and one of the columns is inPk
// the return value are the key matrix, and the index where inPk was put (random).
xmr_amount populateFromBlockchainSimple(ctkeyV & mixRing, const ctkey & inPk, int mixin) {
int index = randXmrAmount(mixin);
int i = 0;
for (i = 0; i <= mixin; i++) {
if (i != index) {
getKeyFromBlockchain(mixRing[i], (size_t)randXmrAmount(1000));
} else {
mixRing[i] = inPk;
}
}
return index;
}
//RingCT protocol
//genRct:
// creates an rctSig with all data necessary to verify the rangeProofs and that the signer owns one of the
@@ -529,6 +595,82 @@ namespace rct {
return genRct(inSk, destinations, amounts, mixRing, base_hash, index);
}
//RCT simple
//for post-rct only
sRctSig genRctSimple(const key &message, const ctkeyV & inSk, const ctkeyV & inPk, const keyV & destinations, const vector<xmr_amount> &inamounts, const vector<xmr_amount> &outamounts, xmr_amount txnFee, const ctkeyM & mixRing, const std::vector<unsigned int> & index) {
CHECK_AND_ASSERT_THROW_MES(inamounts.size() > 0, "Empty inamounts");
CHECK_AND_ASSERT_THROW_MES(inPk.size() == inSk.size(), "Different number of inPk/inSk");
CHECK_AND_ASSERT_THROW_MES(inamounts.size() == inSk.size(), "Different number of inamounts/inSk");
CHECK_AND_ASSERT_THROW_MES(outamounts.size() == destinations.size(), "Different number of amounts/destinations");
CHECK_AND_ASSERT_THROW_MES(index.size() == inSk.size(), "Different number of index/inSk");
CHECK_AND_ASSERT_THROW_MES(mixRing.size() == inSk.size(), "Different number of mixRing/inSk");
for (size_t n = 0; n < mixRing.size(); ++n) {
CHECK_AND_ASSERT_THROW_MES(index[n] < mixRing[n].size(), "Bad index into mixRing");
}
sRctSig rv;
rv.message = message;
rv.outPk.resize(destinations.size());
rv.rangeSigs.resize(destinations.size());
rv.ecdhInfo.resize(destinations.size());
size_t i;
keyV masks(destinations.size()); //sk mask..
ctkeyV outSk(destinations.size());
key sumout = zero();
for (i = 0; i < destinations.size(); i++) {
//add destination to sig
rv.outPk[i].dest = copy(destinations[i]);
//compute range proof
rv.rangeSigs[i] = proveRange(rv.outPk[i].mask, outSk[i].mask, outamounts[i]);
#ifdef DBG
verRange(rv.outPk[i].mask, rv.rangeSigs[i]);
#endif
sc_add(sumout.bytes, outSk[i].mask.bytes, sumout.bytes);
//mask amount and mask
rv.ecdhInfo[i].mask = copy(outSk[i].mask);
rv.ecdhInfo[i].amount = d2h(outamounts[i]);
ecdhEncode(rv.ecdhInfo[i], destinations[i]);
}
//set txn fee
rv.txnFee = txnFee;
// TODO: unused ??
// key txnFeeKey = scalarmultH(d2h(rv.txnFee));
rv.mixRing = mixRing;
rv.pseudoOuts.resize(inamounts.size());
rv.MG.resize(inamounts.size());
key sumpouts = zero(); //sum pseudoOut masks
key a;
for (i = 0 ; i < inamounts.size() - 1; i++) {
skGen(a);
sc_add(sumpouts.bytes, a.bytes, sumpouts.bytes);
genC(rv.pseudoOuts[i], a, inamounts[i]);
rv.MG[i] = proveRctMGSimple(message, rv.mixRing[i], inSk[i], a, rv.pseudoOuts[i], index[i]);
}
rv.mixRing = mixRing;
sc_sub(a.bytes, sumout.bytes, sumpouts.bytes);
genC(rv.pseudoOuts[i], a, inamounts[i]);
DP(rv.pseudoOuts[i]);
rv.MG[i] = proveRctMGSimple(message, rv.mixRing[i], inSk[i], a, rv.pseudoOuts[i], index[i]);
return rv;
}
sRctSig genRctSimple(const key &message, const ctkeyV & inSk, const ctkeyV & inPk, const keyV & destinations, const vector<xmr_amount> &inamounts, const vector<xmr_amount> &outamounts, xmr_amount txnFee, unsigned int mixin) {
std::vector<unsigned int> index;
index.resize(inPk.size());
ctkeyM mixRing;
mixRing.resize(inPk.size());
for (size_t i = 0; i < inPk.size(); ++i) {
mixRing[i].resize(mixin+1);
index[i] = populateFromBlockchainSimple(mixRing[i], inPk[i], mixin);
}
return genRctSimple(message, inSk, inPk, destinations, inamounts, outamounts, txnFee, mixRing, index);
}
//RingCT protocol
//genRct:
// creates an rctSig with all data necessary to verify the rangeProofs and that the signer owns one of the
@@ -572,6 +714,52 @@ namespace rct {
return verRct(rv, rv.mixRing, rv.MG.II, rv.base_hash);
}
//ver RingCT simple
//assumes only post-rct style inputs (at least for max anonymity)
bool verRctSimple(const sRctSig & rv) {
size_t i = 0;
bool rvb = true;
CHECK_AND_ASSERT_MES(rv.outPk.size() == rv.rangeSigs.size(), false, "Mismatched sizes of rv.outPk and rv.rangeSigs");
CHECK_AND_ASSERT_MES(rv.outPk.size() == rv.ecdhInfo.size(), false, "Mismatched sizes of rv.outPk and rv.ecdhInfo");
CHECK_AND_ASSERT_MES(rv.pseudoOuts.size() == rv.MGs.size(), false, "Mismatched sizes of rv.pseudoOuts and rv.MGs");
CHECK_AND_ASSERT_MES(rv.pseudoOuts.size() == rv.mixRing.size(), false, "Mismatched sizes of rv.pseudoOuts and rv.MGs");
key sumOutpks = identity();
for (i = 0; i < rv.outPk.size(); i++) {
if (!verRange(rv.outPk[i].mask, rv.rangeSigs[i])) {
return false;
}
addKeys(sumOutpks, sumOutpks, rv.outPk[i].mask);
}
DP(sumOutpks);
key txnFeeKey = scalarmultH(d2h(rv.txnFee));
addKeys(sumOutpks, txnFeeKey, sumOutpks);
bool tmpb = false;
key sumPseudoOuts = identity();
for (i = 0 ; i < rv.mixRing.size() ; i++) {
tmpb = verRctMGSimple(rv.message, rv.MG[i], rv.MG[i].II, rv.mixRing[i], rv.pseudoOuts[i]);
addKeys(sumPseudoOuts, sumPseudoOuts, rv.pseudoOuts[i]);
DP(tmpb);
if (!tmpb) {
return false;
}
}
DP(sumPseudoOuts);
bool mgVerd = true;
//check pseudoOuts vs Outs..
if (!equalKeys(sumPseudoOuts, sumOutpks)) {
return false;
}
DP("mg sig verified?");
DP(mgVerd);
return (rvb && mgVerd);
}
//RingCT protocol
//genRct:
// creates an rctSig with all data necessary to verify the rangeProofs and that the signer owns one of the
@@ -609,4 +797,27 @@ namespace rct {
key mask;
return decodeRct(rv, sk, i, mask);
}
xmr_amount decodeRct(const sRctSig & rv, const key & sk, unsigned int i) {
CHECK_AND_ASSERT_THROW_MES(rv.rangeSigs.size() > 0, "Empty rv.rangeSigs");
CHECK_AND_ASSERT_THROW_MES(rv.outPk.size() == rv.rangeSigs.size(), "Mismatched sizes of rv.outPk and rv.rangeSigs");
CHECK_AND_ASSERT_THROW_MES(i < rv.ecdhInfo.size(), "Bad index");
//mask amount and mask
ecdhTuple ecdh_info = rv.ecdhInfo[i];
ecdhDecode(ecdh_info, sk);
key mask = ecdh_info.mask;
key amount = ecdh_info.amount;
key C = rv.outPk[i].mask;
DP("C");
DP(C);
key Ctmp;
addKeys2(Ctmp, mask, amount, H);
DP("Ctmp");
DP(Ctmp);
if (equalKeys(C, Ctmp) == false) {
CHECK_AND_ASSERT_THROW_MES(false, "warning, amount decoded incorrectly, will be unable to spend");
}
return h2d(amount);
}
}