bitcoin · denavila · Oct 20, 2023
diff --git a/src/interfaces/wallet.h b/src/interfaces/wallet.h
@@ -158,6 +158,16 @@ class Wallet
         WalletValueMap value_map,
         WalletOrderForm order_form) = 0;
 
+    virtual std::pair<unsigned int, bool> calculateDeniabilizationCycles(const COutPoint& outpoint) = 0;
+
+    virtual util::Result<CTransactionRef> createDeniabilizationTransaction(const std::set<COutPoint>& inputs,
+                                                                           const std::optional<OutputType>& opt_output_type,
+                                                                           unsigned int confirm_target,
+                                                                           unsigned int deniabilization_cycles,
+                                                                           bool sign,
+                                                                           bool& insufficient_amount,
+                                                                           CAmount& fee) = 0;
+
     //! Return whether transaction can be abandoned.
     virtual bool transactionCanBeAbandoned(const uint256& txid) = 0;
 
@@ -184,6 +194,13 @@ class Wallet
         std::vector<bilingual_str>& errors,
         uint256& bumped_txid) = 0;
 
+    //! Create a fee bump transaction for a deniabilization transaction
+    virtual util::Result<CTransactionRef> createBumpDeniabilizationTransaction(const uint256& txid,
+                                                                               unsigned int confirm_target,
+                                                                               bool sign,
+                                                                               CAmount& old_fee,
+                                                                               CAmount& new_fee) = 0;
+
     //! Get a transaction.
     virtual CTransactionRef getTx(const uint256& txid) = 0;
 
@@ -255,6 +272,9 @@ class Wallet
         int* returned_target,
         FeeReason* reason) = 0;
 
+    //! Get the fee rate for deniabilization
+    virtual CFeeRate getDeniabilizationFeeRate(unsigned int confirm_target) = 0;
+
     //! Get tx confirm target.
     virtual unsigned int getConfirmTarget() = 0;
 

diff --git a/src/rpc/client.cpp b/src/rpc/client.cpp
@@ -167,6 +167,9 @@ static const CRPCConvertParam vRPCConvertParams[] =
     { "walletcreatefundedpsbt", 3, "solving_data"},
     { "walletcreatefundedpsbt", 3, "max_tx_weight"},
     { "walletcreatefundedpsbt", 4, "bip32derivs" },
+    { "walletdeniabilizecoin", 0, "inputs" },
+    { "walletdeniabilizecoin", 2, "conf_target" },
+    { "walletdeniabilizecoin", 3, "add_to_wallet" },
     { "walletprocesspsbt", 1, "sign" },
     { "walletprocesspsbt", 3, "bip32derivs" },
     { "walletprocesspsbt", 4, "finalize" },

diff --git a/src/wallet/feebumper.cpp b/src/wallet/feebumper.cpp
@@ -387,5 +387,103 @@ Result CommitTransaction(CWallet& wallet, const uint256& txid, CMutableTransacti
     return Result::OK;
 }
 
+Result CreateRateBumpDeniabilizationTransaction(CWallet& wallet, const uint256& txid, unsigned int confirm_target, bool sign, bilingual_str& error, CAmount& old_fee, CAmount& new_fee, CTransactionRef& new_tx)
+{
+    CCoinControl coin_control = SetupDeniabilizationCoinControl(confirm_target);
+    coin_control.m_feerate = CalculateDeniabilizationFeeRate(wallet, confirm_target);
+
+    LOCK(wallet.cs_wallet);
+
+    auto it = wallet.mapWallet.find(txid);
+    if (it == wallet.mapWallet.end()) {
+        error = Untranslated("Invalid or non-wallet transaction id");
+        return Result::INVALID_ADDRESS_OR_KEY;
+    }
+    const CWalletTx& wtx = it->second;
+
+    // Retrieve all of the UTXOs and add them to coin control
+    // While we're here, calculate the input amount
+    std::map<COutPoint, Coin> coins;
+    CAmount input_value = 0;
+    for (const CTxIn& txin : wtx.tx->vin) {
+        coins[txin.prevout]; // Create empty map entry keyed by prevout.
+    }
+    wallet.chain().findCoins(coins);
+    for (const CTxIn& txin : wtx.tx->vin) {
+        const Coin& coin = coins.at(txin.prevout);
+        if (coin.out.IsNull()) {
+            error = Untranslated(strprintf("%s:%u is already spent", txin.prevout.hash.GetHex(), txin.prevout.n));
+            return Result::MISC_ERROR;
+        }
+        if (!wallet.IsMine(txin.prevout)) {
+            error = Untranslated("All inputs must be from our wallet.");
+            return Result::MISC_ERROR;
+        }
+        coin_control.Select(txin.prevout);
+        input_value += coin.out.nValue;
+    }
+
+    std::vector<bilingual_str> dymmy_errors;
+    Result result = PreconditionChecks(wallet, wtx, /*require_mine=*/true, dymmy_errors);
+    if (result != Result::OK) {
+        error = dymmy_errors.front();
+        return result;
+    }
+
+    // Calculate the old output amount.
+    CAmount output_value = 0;
+    for (const auto& old_output : wtx.tx->vout) {
+        output_value += old_output.nValue;
+    }
+
+    old_fee = input_value - output_value;
+
+    std::vector<CRecipient> recipients;
+    for (const auto& output : wtx.tx->vout) {
+        CTxDestination destination = CNoDestination();
+        ExtractDestination(output.scriptPubKey, destination);
+        CRecipient recipient = {destination, output.nValue, false};
+        recipients.push_back(recipient);
+    }
+    // the last recipient gets the old fee
+    recipients.back().nAmount += old_fee;
+    // and pays the new fee
+    recipients.back().fSubtractFeeFromAmount = true;
+    // we don't expect to get change, but we provide the address to prevent CreateTransactionInternal from generating a change address
+    coin_control.destChange = recipients.back().dest;
+
+    for (const auto& inputs : wtx.tx->vin) {
+        coin_control.Select(COutPoint(inputs.prevout));
+    }
+
+    auto res = CreateTransaction(wallet, recipients, std::nullopt, coin_control, /*sign=*/false);
+    if (!res) {
+        error = util::ErrorString(res);
+        return Result::WALLET_ERROR;
+    }
+
+    // make sure we didn't get a change position assigned (we don't expect to use the channge address)
+    Assert(!res->change_pos.has_value());
+
+    // spoof the transaction fingerprint to increase the transaction privacy
+    {
+        FastRandomContext rng_fast;
+        CMutableTransaction spoofedTx(*res->tx);
+        SpoofTransactionFingerprint(spoofedTx, rng_fast, coin_control.m_signal_bip125_rbf);
+        if (sign && !wallet.SignTransaction(spoofedTx)) {
+            error = Untranslated("Signing the deniabilization fee bump transaction failed.");
+            return Result::MISC_ERROR;
+        }
+        // store the spoofed transaction in the result
+        res->tx = MakeTransactionRef(std::move(spoofedTx));
+    }
+
+    // write back the new fee
+    new_fee = res->fee;
+    // write back the transaction
+    new_tx = res->tx;
+    return Result::OK;
+}
+
 } // namespace feebumper
 } // namespace wallet
diff --git a/src/wallet/feebumper.h b/src/wallet/feebumper.h
@@ -72,6 +72,15 @@ Result CommitTransaction(CWallet& wallet,
     std::vector<bilingual_str>& errors,
     uint256& bumped_txid);
 
+Result CreateRateBumpDeniabilizationTransaction(CWallet& wallet,
+                                                const uint256& txid,
+                                                unsigned int confirm_target,
+                                                bool sign,
+                                                bilingual_str& error,
+                                                CAmount& old_fee,
+                                                CAmount& new_fee,
+                                                CTransactionRef& new_tx);
+
 struct SignatureWeights
 {
 private:

diff --git a/src/wallet/interfaces.cpp b/src/wallet/interfaces.cpp
@@ -299,6 +299,28 @@ class WalletImpl : public Wallet
         LOCK(m_wallet->cs_wallet);
         m_wallet->CommitTransaction(std::move(tx), std::move(value_map), std::move(order_form));
     }
+    std::pair<unsigned int, bool> calculateDeniabilizationCycles(const COutPoint& outpoint) override
+    {
+        LOCK(m_wallet->cs_wallet); // TODO - Do we need a lock here?
+        return CalculateDeniabilizationCycles(*m_wallet, outpoint);
+    }
+    util::Result<CTransactionRef> createDeniabilizationTransaction(const std::set<COutPoint>& inputs,
+                                                                   const std::optional<OutputType>& opt_output_type,
+                                                                   unsigned int confirm_target,
+                                                                   unsigned int deniabilization_cycles,
+                                                                   bool sign,
+                                                                   bool& insufficient_amount,
+                                                                   CAmount& fee) override
+    {
+        LOCK(m_wallet->cs_wallet); // TODO - Do we need a lock here?
+        auto res = CreateDeniabilizationTransaction(*m_wallet, inputs, opt_output_type, confirm_target, deniabilization_cycles, sign, insufficient_amount);
+        if (!res) {
+            return util::Error{util::ErrorString(res)};
+        }
+        const auto& txr = *res;
+        fee = txr.fee;
+        return txr.tx;
+    }
     bool transactionCanBeAbandoned(const uint256& txid) override { return m_wallet->TransactionCanBeAbandoned(txid); }
     bool abandonTransaction(const uint256& txid) override
     {
@@ -328,6 +350,20 @@ class WalletImpl : public Wallet
         return feebumper::CommitTransaction(*m_wallet.get(), txid, std::move(mtx), errors, bumped_txid) ==
                feebumper::Result::OK;
     }
+    util::Result<CTransactionRef> createBumpDeniabilizationTransaction(const uint256& txid,
+                                                                       unsigned int confirm_target,
+                                                                       bool sign,
+                                                                       CAmount& old_fee,
+                                                                       CAmount& new_fee) override
+    {
+        bilingual_str error;
+        CTransactionRef new_tx;
+        auto res = feebumper::CreateRateBumpDeniabilizationTransaction(*m_wallet.get(), txid, confirm_target, sign, error, old_fee, new_fee, new_tx);
+        if (res != feebumper::Result::OK) {
+            return util::Error{error};
+        }
+        return new_tx;
+    }
     CTransactionRef getTx(const uint256& txid) override
     {
         LOCK(m_wallet->cs_wallet);
@@ -510,6 +546,10 @@ class WalletImpl : public Wallet
         if (reason) *reason = fee_calc.reason;
         return result;
     }
+    CFeeRate getDeniabilizationFeeRate(unsigned int confirm_target) override
+    {
+        return CalculateDeniabilizationFeeRate(*m_wallet, confirm_target);
+    }
     unsigned int getConfirmTarget() override { return m_wallet->m_confirm_target; }
     bool hdEnabled() override { return m_wallet->IsHDEnabled(); }
     bool canGetAddresses() override { return m_wallet->CanGetAddresses(); }

diff --git a/src/wallet/rpc/spend.cpp b/src/wallet/rpc/spend.cpp
@@ -1784,4 +1784,129 @@ RPCHelpMan walletcreatefundedpsbt()
 },
     };
 }
+
+// clang-format off
+RPCHelpMan walletdeniabilizecoin()
+{
+    return RPCHelpMan{"walletdeniabilizecoin",
+        "\nDeniabilize one or more UTXOs that share the same address.\n",
+        {
+            {"inputs", RPCArg::Type::ARR, RPCArg::Default{UniValue::VARR}, "Specify inputs (must share the same address). A JSON array of JSON objects",
+                {
+                    {"txid", RPCArg::Type::STR_HEX, RPCArg::Optional::NO, "The transaction id"},
+                    {"vout", RPCArg::Type::NUM, RPCArg::Optional::NO, "The output number"},
+                },
+            },
+            {"output_type", RPCArg::Type::STR, RPCArg::Optional::OMITTED, "Optional output type to use. Options are \"legacy\", \"p2sh-segwit\", \"bech32\" and \"bech32m\". If not specified the output type is inferred from the inputs."},
+            {"conf_target", RPCArg::Type::NUM, RPCArg::DefaultHint{"wallet -txconfirmtarget"}, "Confirmation target in blocks"},
+            {"add_to_wallet", RPCArg::Type::BOOL, RPCArg::Default{true}, "When false, returns the serialized transaction without broadcasting or adding it to the wallet"},
+        },
+        RPCResult{
+            RPCResult::Type::OBJ, "", "",
+                {
+                    {RPCResult::Type::STR_HEX, "txid", "The deniabilization transaction id."},
+                    {RPCResult::Type::STR_AMOUNT, "fee", "The fee used in the deniabilization transaction."},
+                    {RPCResult::Type::STR_HEX, "hex", /*optional=*/true, "If add_to_wallet is false, the hex-encoded raw transaction with signature(s)"},
+                }
+        },
+        RPCExamples{
+            "\nDeniabilize a single UTXO\n"
+            + HelpExampleCli("walletdeniabilizecoin", "'[{\"txid\":\"4c14d20709daef476854fe7ef75bdfcfd5a7636a431b4622ec9481f297e12e8c\", \"vout\": 0}]'") +
+            "\nDeniabilize a single UTXO using a specific output type\n"
+            + HelpExampleCli("walletdeniabilizecoin", "'[{\"txid\":\"4c14d20709daef476854fe7ef75bdfcfd5a7636a431b4622ec9481f297e12e8c\", \"vout\": 0}]' bech32") +
+            "\nDeniabilize a single UTXO with an explicit confirmation target\n"
+            + HelpExampleCli("walletdeniabilizecoin", "'[{\"txid\":\"4c14d20709daef476854fe7ef75bdfcfd5a7636a431b4622ec9481f297e12e8c\", \"vout\": 0}]' null 144") +
+            "\nDeniabilize a single UTXO without broadcasting the transaction\n"
+            + HelpExampleCli("walletdeniabilizecoin", "'[{\"txid\":\"4c14d20709daef476854fe7ef75bdfcfd5a7636a431b4622ec9481f297e12e8c\", \"vout\": 0}]' null 6 false")
+        },
+        [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
+        {
+            std::shared_ptr<CWallet> const pwallet = GetWalletForJSONRPCRequest(request);
+            if (!pwallet) return UniValue::VNULL;
+
+            std::optional<CScript> shared_script;
+            std::set<COutPoint> inputs;
+            unsigned int deniabilization_cycles = UINT_MAX;
+            for (const UniValue& input : request.params[0].get_array().getValues()) {
+                Txid txid = Txid::FromUint256(ParseHashO(input, "txid"));
+
+                const UniValue& vout_v = input.find_value("vout");
+                if (!vout_v.isNum()) {
+                    throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid parameter, missing vout key");
+                }
+                int nOutput = vout_v.getInt<int>();
+                if (nOutput < 0) {
+                    throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid parameter, vout cannot be negative");
+                }
+
+                COutPoint outpoint(txid, nOutput);
+                LOCK(pwallet->cs_wallet);
+                auto walletTx = pwallet->GetWalletTx(outpoint.hash);
+                if (!walletTx) {
+                    throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid parameter, txid not found in wallet.");
+                }
+                if (outpoint.n >= walletTx->tx->vout.size()) {
+                    throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid parameter, vout is out of range");
+                }
+                const auto& output = walletTx->tx->vout[outpoint.n];
+
+                isminetype mine = pwallet->IsMine(output);
+                if (mine == ISMINE_NO) {
+                    throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid parameter, transaction's output doesn't belong to this wallet.");
+                }
+
+                bool spendable = (mine & ISMINE_SPENDABLE) != ISMINE_NO;
+                if (spendable) {
+                    auto script = FindNonChangeParentOutput(*pwallet, outpoint).scriptPubKey;
+                    if (!shared_script) {
+                        shared_script = script;
+                    }
+                    else if (!(*shared_script == script)) {
+                        throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid parameter, inputs must share the same address");
+                    }
+                } else {
+                    throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid parameter, inputs must be spendable and have a valid address");
+                }
+
+                inputs.emplace(outpoint);
+                auto cycles_res = CalculateDeniabilizationCycles(*pwallet, outpoint);
+                deniabilization_cycles = std::min(deniabilization_cycles, cycles_res.first);
+            }
+
+            if (inputs.empty()) {
+                throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid parameter, inputs must not be empty");
+            }
+
+            std::optional<OutputType> opt_output_type = !request.params[1].isNull() ? ParseOutputType(request.params[1].get_str()) : std::nullopt;
+            unsigned int confirm_target = !request.params[2].isNull() ? request.params[2].getInt<unsigned int>() : pwallet->m_confirm_target;
+            const bool add_to_wallet = !request.params[3].isNull() ? request.params[3].get_bool() : true;
+
+            CTransactionRef tx;
+            CAmount tx_fee = 0;
+            {
+                bool sign = !pwallet->IsWalletFlagSet(WALLET_FLAG_DISABLE_PRIVATE_KEYS);
+                bool insufficient_amount = false;
+                auto res = CreateDeniabilizationTransaction(*pwallet, inputs, opt_output_type, confirm_target, deniabilization_cycles, sign, insufficient_amount);
+                if (!res) {
+                    throw JSONRPCError(RPC_TRANSACTION_ERROR, ErrorString(res).original);
+                }
+                tx = res->tx;
+                tx_fee = res->fee;
+            }
+
+            UniValue result(UniValue::VOBJ);
+            result.pushKV("txid", tx->GetHash().GetHex());
+            if (add_to_wallet) {
+                pwallet->CommitTransaction(tx, {}, /*orderForm=*/{});
+            } else {
+                std::string hex{EncodeHexTx(*tx)};
+                result.pushKV("hex", hex);
+            }
+            result.pushKV("fee", ValueFromAmount(tx_fee));
+            return result;
+        }
+    };
+}
+// clang-format on
+
 } // namespace wallet
diff --git a/src/wallet/rpc/wallet.cpp b/src/wallet/rpc/wallet.cpp
@@ -1083,6 +1083,7 @@ RPCHelpMan send();
 RPCHelpMan sendall();
 RPCHelpMan walletprocesspsbt();
 RPCHelpMan walletcreatefundedpsbt();
+RPCHelpMan walletdeniabilizecoin();
 RPCHelpMan signrawtransactionwithwallet();
 
 // signmessage
@@ -1172,6 +1173,7 @@ Span<const CRPCCommand> GetWalletRPCCommands()
         {"wallet", &walletpassphrase},
         {"wallet", &walletpassphrasechange},
         {"wallet", &walletprocesspsbt},
+        {"wallet", &walletdeniabilizecoin},
     };
     return commands;
 }