comments

include/xrpl/protocol/ConfidentialTransfer.h

@@ -356,19 +356,6 @@ verifyClawbackProof(
     Slice const& ciphertext,
     uint256 const& contextHash);
 
-/**
- * @brief Generates a cryptographically secure blinding factor
- * (size=xrpl::kEcBlindingFactorLength).
- *
- * Produces random bytes suitable for use as an ElGamal blinding factor
- * or Pedersen commitment randomness.
- *
- * @return A buffer containing the random blinding factor
- *         (size=xrpl::kEcBlindingFactorLength).
- */
-Buffer
-generateBlindingFactor();
-
 /**
  * @brief Verifies all zero-knowledge proofs for a ConfidentialMPTSend transaction.
  *

include/xrpl/protocol/detail/sfields.macro

@@ -207,8 +207,8 @@ TYPED_SFIELD(sfParentBatchID,            UINT256,   36)
 TYPED_SFIELD(sfLoanBrokerID,             UINT256,   37,
     SField::kSmdPseudoAccount | SField::kSmdDefault)
 TYPED_SFIELD(sfLoanID,                   UINT256,   38)
-TYPED_SFIELD(sfBlindingFactor,           UINT256,   39)
-TYPED_SFIELD(sfReferenceHolding,         UINT256,   40)
+TYPED_SFIELD(sfReferenceHolding,         UINT256,   39)
+TYPED_SFIELD(sfBlindingFactor,           UINT256,   40)
 
 // number (common)
 TYPED_SFIELD(sfNumber,                   NUMBER,     1)

src/libxrpl/protocol/ConfidentialTransfer.cpp

@@ -1,9 +1,11 @@
 #include <xrpl/protocol/ConfidentialTransfer.h>
 
 #include <xrpl/basics/Buffer.h>
+#include <xrpl/basics/Log.h>
 #include <xrpl/basics/Slice.h>
 #include <xrpl/basics/base_uint.h>
 #include <xrpl/basics/contract.h>
+#include <xrpl/basics/strHex.h>
 #include <xrpl/protocol/AccountID.h>
 #include <xrpl/protocol/Protocol.h>
 #include <xrpl/protocol/SField.h>
@@ -197,6 +199,8 @@ homomorphicAdd(Slice const& a, Slice const& b)
             secp256k1Context(), &sum.c1, &sum.c2, &pairA->c1, &pairA->c2, &pairB->c1, &pairB->c2);
         res != 1)
     {
+        JLOG(debugLog().error()) << "homomorphicAdd: secp256k1_elgamal_add failed"
+                                 << " a=" << strHex(a) << " b=" << strHex(b);
         return std::nullopt;
     }
 
@@ -220,6 +224,8 @@ homomorphicSubtract(Slice const& a, Slice const& b)
             secp256k1Context(), &diff.c1, &diff.c2, &pairA->c1, &pairA->c2, &pairB->c1, &pairB->c2);
         res != 1)
     {
+        JLOG(debugLog().error()) << "homomorphicSubtract: secp256k1_elgamal_subtract failed"
+                                 << " a=" << strHex(a) << " b=" << strHex(b);
         return std::nullopt;
     }
 
@@ -236,18 +242,6 @@ rerandomizeCiphertext(Slice const& ciphertext, Slice const& pubKeySlice, Slice c
     return homomorphicAdd(ciphertext, *zero);
 }
 
-Buffer
-generateBlindingFactor()
-{
-    unsigned char blindingFactor[kEcBlindingFactorLength];
-
-    // todo: might need to be updated using another RNG
-    if (RAND_bytes(blindingFactor, kEcBlindingFactorLength) != 1)
-        Throw<std::runtime_error>("Failed to generate random number");
-
-    return Buffer(blindingFactor, kEcBlindingFactorLength);
-}
-
 std::optional<Buffer>
 encryptAmount(uint64_t const amt, Slice const& pubKeySlice, Slice const& blindingFactor)
 {

src/test/jtx/ConfidentialTransfer.h

@@ -239,9 +239,9 @@ class ConfidentialTransferTestBase : public beast::unit_test::Suite
             : sendAmount(amount)
             , nRecipients(auditor ? 4 : 3)
             , version(mpt.getMPTokenVersion(sender))
-            , blindingFactor(generateBlindingFactor())
+            , blindingFactor(test::jtx::generateBlindingFactor())
             , amountBlindingFactor(blindingFactor)
-            , balanceBlindingFactor(generateBlindingFactor())
+            , balanceBlindingFactor(test::jtx::generateBlindingFactor())
             , senderAmt(mpt.encryptAmount(sender, amount, blindingFactor))
             , destAmt(mpt.encryptAmount(dest, amount, blindingFactor))
             , issuerAmt(mpt.encryptAmount(issuer, amount, blindingFactor))

src/test/jtx/mpt.h

@@ -14,12 +14,35 @@
 #include <xrpl/protocol/UintTypes.h>
 #include <xrpl/protocol/XRPAmount.h>
 
+#include <openssl/rand.h>
+
 #include <cstddef>
 #include <cstdint>
 #include <cstring>
 
 namespace xrpl::test::jtx {
 
+/**
+ * @brief Generates a cryptographically secure blinding factor
+ * (size=xrpl::kEcBlindingFactorLength).
+ *
+ * Produces random bytes suitable for use as an ElGamal blinding factor
+ * or Pedersen commitment randomness.
+ *
+ * @return A buffer containing the random blinding factor
+ *         (size=xrpl::kEcBlindingFactorLength).
+ */
+inline Buffer
+generateBlindingFactor()
+{
+    unsigned char blindingFactor[kEcBlindingFactorLength];
+
+    if (RAND_bytes(blindingFactor, kEcBlindingFactorLength) != 1)
+        Throw<std::runtime_error>("Failed to generate random number");
+
+    return Buffer(blindingFactor, kEcBlindingFactorLength);
+}
+
 class MPTTester;
 
 auto const kMptDexFlags = tfMPTCanTrade | tfMPTCanTransfer;