Move PSBT definitions and code to separate files

Move non-wallet PSBT code to src/psbt.{h,cpp}, and PSBT wallet code to
src/wallet/psbtwallet.{h,cpp}. This commit contains only code movement (and
adjustments to includes and Makefile.am.)

12 files changed, 862 insertions, 816 deletions

diff --git a/src/Makefile.am b/src/Makefile.am
index 9a87af2efc..7490d8b790 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -162,6 +162,7 @@ BITCOIN_CORE_H = \
   policy/rbf.h \
   pow.h \
   protocol.h \
+  psbt.h \
   random.h \
   reverse_iterator.h \
   reverselock.h \
@@ -210,6 +211,7 @@ BITCOIN_CORE_H = \
   wallet/db.h \
   wallet/feebumper.h \
   wallet/fees.h \
+  wallet/psbtwallet.h \
   wallet/rpcwallet.h \
   wallet/wallet.h \
   wallet/walletdb.h \
@@ -310,6 +312,7 @@ libbitcoin_wallet_a_SOURCES = \
   wallet/feebumper.cpp \
   wallet/fees.cpp \
   wallet/init.cpp \
+  wallet/psbtwallet.cpp \
   wallet/rpcdump.cpp \
   wallet/rpcwallet.cpp \
   wallet/wallet.cpp \
@@ -423,6 +426,7 @@ libbitcoin_common_a_SOURCES = \
   netaddress.cpp \
   netbase.cpp \
   policy/feerate.cpp \
+  psbt.cpp \
   protocol.cpp \
   scheduler.cpp \
   script/descriptor.cpp \
diff --git a/src/core_read.cpp b/src/core_read.cpp
index 0379098712..536a7f4f17 100644
--- a/src/core_read.cpp
+++ b/src/core_read.cpp
@@ -4,6 +4,7 @@
 
 #include <core_io.h>
 
+#include <psbt.h>
 #include <primitives/block.h>
 #include <primitives/transaction.h>
 #include <script/script.h>
diff --git a/src/psbt.cpp b/src/psbt.cpp
new file mode 100644
index 0000000000..97fb39f1c8
--- /dev/null
+++ b/src/psbt.cpp
@@ -0,0 +1,227 @@
+// Copyright (c) 2009-2018 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <psbt.h>
+#include <util/strencodings.h>
+
+PartiallySignedTransaction::PartiallySignedTransaction(const CMutableTransaction& tx) : tx(tx)
+{
+    inputs.resize(tx.vin.size());
+    outputs.resize(tx.vout.size());
+}
+
+bool PartiallySignedTransaction::IsNull() const
+{
+    return !tx && inputs.empty() && outputs.empty() && unknown.empty();
+}
+
+void PartiallySignedTransaction::Merge(const PartiallySignedTransaction& psbt)
+{
+    for (unsigned int i = 0; i < inputs.size(); ++i) {
+        inputs[i].Merge(psbt.inputs[i]);
+    }
+    for (unsigned int i = 0; i < outputs.size(); ++i) {
+        outputs[i].Merge(psbt.outputs[i]);
+    }
+    unknown.insert(psbt.unknown.begin(), psbt.unknown.end());
+}
+
+bool PartiallySignedTransaction::IsSane() const
+{
+    for (PSBTInput input : inputs) {
+        if (!input.IsSane()) return false;
+    }
+    return true;
+}
+
+bool PSBTInput::IsNull() const
+{
+    return !non_witness_utxo && witness_utxo.IsNull() && partial_sigs.empty() && unknown.empty() && hd_keypaths.empty() && redeem_script.empty() && witness_script.empty();
+}
+
+void PSBTInput::FillSignatureData(SignatureData& sigdata) const
+{
+    if (!final_script_sig.empty()) {
+        sigdata.scriptSig = final_script_sig;
+        sigdata.complete = true;
+    }
+    if (!final_script_witness.IsNull()) {
+        sigdata.scriptWitness = final_script_witness;
+        sigdata.complete = true;
+    }
+    if (sigdata.complete) {
+        return;
+    }
+
+    sigdata.signatures.insert(partial_sigs.begin(), partial_sigs.end());
+    if (!redeem_script.empty()) {
+        sigdata.redeem_script = redeem_script;
+    }
+    if (!witness_script.empty()) {
+        sigdata.witness_script = witness_script;
+    }
+    for (const auto& key_pair : hd_keypaths) {
+        sigdata.misc_pubkeys.emplace(key_pair.first.GetID(), key_pair);
+    }
+}
+
+void PSBTInput::FromSignatureData(const SignatureData& sigdata)
+{
+    if (sigdata.complete) {
+        partial_sigs.clear();
+        hd_keypaths.clear();
+        redeem_script.clear();
+        witness_script.clear();
+
+        if (!sigdata.scriptSig.empty()) {
+            final_script_sig = sigdata.scriptSig;
+        }
+        if (!sigdata.scriptWitness.IsNull()) {
+            final_script_witness = sigdata.scriptWitness;
+        }
+        return;
+    }
+
+    partial_sigs.insert(sigdata.signatures.begin(), sigdata.signatures.end());
+    if (redeem_script.empty() && !sigdata.redeem_script.empty()) {
+        redeem_script = sigdata.redeem_script;
+    }
+    if (witness_script.empty() && !sigdata.witness_script.empty()) {
+        witness_script = sigdata.witness_script;
+    }
+    for (const auto& entry : sigdata.misc_pubkeys) {
+        hd_keypaths.emplace(entry.second);
+    }
+}
+
+void PSBTInput::Merge(const PSBTInput& input)
+{
+    if (!non_witness_utxo && input.non_witness_utxo) non_witness_utxo = input.non_witness_utxo;
+    if (witness_utxo.IsNull() && !input.witness_utxo.IsNull()) {
+        witness_utxo = input.witness_utxo;
+        non_witness_utxo = nullptr; // Clear out any non-witness utxo when we set a witness one.
+    }
+
+    partial_sigs.insert(input.partial_sigs.begin(), input.partial_sigs.end());
+    hd_keypaths.insert(input.hd_keypaths.begin(), input.hd_keypaths.end());
+    unknown.insert(input.unknown.begin(), input.unknown.end());
+
+    if (redeem_script.empty() && !input.redeem_script.empty()) redeem_script = input.redeem_script;
+    if (witness_script.empty() && !input.witness_script.empty()) witness_script = input.witness_script;
+    if (final_script_sig.empty() && !input.final_script_sig.empty()) final_script_sig = input.final_script_sig;
+    if (final_script_witness.IsNull() && !input.final_script_witness.IsNull()) final_script_witness = input.final_script_witness;
+}
+
+bool PSBTInput::IsSane() const
+{
+    // Cannot have both witness and non-witness utxos
+    if (!witness_utxo.IsNull() && non_witness_utxo) return false;
+
+    // If we have a witness_script or a scriptWitness, we must also have a witness utxo
+    if (!witness_script.empty() && witness_utxo.IsNull()) return false;
+    if (!final_script_witness.IsNull() && witness_utxo.IsNull()) return false;
+
+    return true;
+}
+
+void PSBTOutput::FillSignatureData(SignatureData& sigdata) const
+{
+    if (!redeem_script.empty()) {
+        sigdata.redeem_script = redeem_script;
+    }
+    if (!witness_script.empty()) {
+        sigdata.witness_script = witness_script;
+    }
+    for (const auto& key_pair : hd_keypaths) {
+        sigdata.misc_pubkeys.emplace(key_pair.first.GetID(), key_pair);
+    }
+}
+
+void PSBTOutput::FromSignatureData(const SignatureData& sigdata)
+{
+    if (redeem_script.empty() && !sigdata.redeem_script.empty()) {
+        redeem_script = sigdata.redeem_script;
+    }
+    if (witness_script.empty() && !sigdata.witness_script.empty()) {
+        witness_script = sigdata.witness_script;
+    }
+    for (const auto& entry : sigdata.misc_pubkeys) {
+        hd_keypaths.emplace(entry.second);
+    }
+}
+
+bool PSBTOutput::IsNull() const
+{
+    return redeem_script.empty() && witness_script.empty() && hd_keypaths.empty() && unknown.empty();
+}
+
+void PSBTOutput::Merge(const PSBTOutput& output)
+{
+    hd_keypaths.insert(output.hd_keypaths.begin(), output.hd_keypaths.end());
+    unknown.insert(output.unknown.begin(), output.unknown.end());
+
+    if (redeem_script.empty() && !output.redeem_script.empty()) redeem_script = output.redeem_script;
+    if (witness_script.empty() && !output.witness_script.empty()) witness_script = output.witness_script;
+}
+
+bool PSBTInputSigned(PSBTInput& input)
+{
+    return !input.final_script_sig.empty() || !input.final_script_witness.IsNull();
+}
+
+bool SignPSBTInput(const SigningProvider& provider, PartiallySignedTransaction& psbt, int index, int sighash)
+{
+    PSBTInput& input = psbt.inputs.at(index);
+    const CMutableTransaction& tx = *psbt.tx;
+
+    if (PSBTInputSigned(input)) {
+        return true;
+    }
+
+    // Fill SignatureData with input info
+    SignatureData sigdata;
+    input.FillSignatureData(sigdata);
+
+    // Get UTXO
+    bool require_witness_sig = false;
+    CTxOut utxo;
+
+    // Verify input sanity, which checks that at most one of witness or non-witness utxos is provided.
+    if (!input.IsSane()) {
+        return false;
+    }
+
+    if (input.non_witness_utxo) {
+        // If we're taking our information from a non-witness UTXO, verify that it matches the prevout.
+        COutPoint prevout = tx.vin[index].prevout;
+        if (input.non_witness_utxo->GetHash() != prevout.hash) {
+            return false;
+        }
+        utxo = input.non_witness_utxo->vout[prevout.n];
+    } else if (!input.witness_utxo.IsNull()) {
+        utxo = input.witness_utxo;
+        // When we're taking our information from a witness UTXO, we can't verify it is actually data from
+        // the output being spent. This is safe in case a witness signature is produced (which includes this
+        // information directly in the hash), but not for non-witness signatures. Remember that we require
+        // a witness signature in this situation.
+        require_witness_sig = true;
+    } else {
+        return false;
+    }
+
+    MutableTransactionSignatureCreator creator(&tx, index, utxo.nValue, sighash);
+    sigdata.witness = false;
+    bool sig_complete = ProduceSignature(provider, creator, utxo.scriptPubKey, sigdata);
+    // Verify that a witness signature was produced in case one was required.
+    if (require_witness_sig && !sigdata.witness) return false;
+    input.FromSignatureData(sigdata);
+
+    // If we have a witness signature, use the smaller witness UTXO.
+    if (sigdata.witness) {
+        input.witness_utxo = utxo;
+        input.non_witness_utxo = nullptr;
+    }
+
+    return sig_complete;
+}
diff --git a/src/psbt.h b/src/psbt.h
new file mode 100644
index 0000000000..fbe55ca100
--- /dev/null
+++ b/src/psbt.h
@@ -0,0 +1,553 @@
+// Copyright (c) 2009-2018 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_PSBT_H
+#define BITCOIN_PSBT_H
+
+#include <attributes.h>
+#include <primitives/transaction.h>
+#include <pubkey.h>
+#include <script/sign.h>
+
+// Magic bytes
+static constexpr uint8_t PSBT_MAGIC_BYTES[5] = {'p', 's', 'b', 't', 0xff};
+
+// Global types
+static constexpr uint8_t PSBT_GLOBAL_UNSIGNED_TX = 0x00;
+
+// Input types
+static constexpr uint8_t PSBT_IN_NON_WITNESS_UTXO = 0x00;
+static constexpr uint8_t PSBT_IN_WITNESS_UTXO = 0x01;
+static constexpr uint8_t PSBT_IN_PARTIAL_SIG = 0x02;
+static constexpr uint8_t PSBT_IN_SIGHASH = 0x03;
+static constexpr uint8_t PSBT_IN_REDEEMSCRIPT = 0x04;
+static constexpr uint8_t PSBT_IN_WITNESSSCRIPT = 0x05;
+static constexpr uint8_t PSBT_IN_BIP32_DERIVATION = 0x06;
+static constexpr uint8_t PSBT_IN_SCRIPTSIG = 0x07;
+static constexpr uint8_t PSBT_IN_SCRIPTWITNESS = 0x08;
+
+// Output types
+static constexpr uint8_t PSBT_OUT_REDEEMSCRIPT = 0x00;
+static constexpr uint8_t PSBT_OUT_WITNESSSCRIPT = 0x01;
+static constexpr uint8_t PSBT_OUT_BIP32_DERIVATION = 0x02;
+
+// The separator is 0x00. Reading this in means that the unserializer can interpret it
+// as a 0 length key which indicates that this is the separator. The separator has no value.
+static constexpr uint8_t PSBT_SEPARATOR = 0x00;
+
+/** A structure for PSBTs which contain per-input information */
+struct PSBTInput
+{
+    CTransactionRef non_witness_utxo;
+    CTxOut witness_utxo;
+    CScript redeem_script;
+    CScript witness_script;
+    CScript final_script_sig;
+    CScriptWitness final_script_witness;
+    std::map<CPubKey, KeyOriginInfo> hd_keypaths;
+    std::map<CKeyID, SigPair> partial_sigs;
+    std::map<std::vector<unsigned char>, std::vector<unsigned char>> unknown;
+    int sighash_type = 0;
+
+    bool IsNull() const;
+    void FillSignatureData(SignatureData& sigdata) const;
+    void FromSignatureData(const SignatureData& sigdata);
+    void Merge(const PSBTInput& input);
+    bool IsSane() const;
+    PSBTInput() {}
+
+    template <typename Stream>
+    inline void Serialize(Stream& s) const {
+        // Write the utxo
+        // If there is a non-witness utxo, then don't add the witness one.
+        if (non_witness_utxo) {
+            SerializeToVector(s, PSBT_IN_NON_WITNESS_UTXO);
+            OverrideStream<Stream> os(&s, s.GetType(), s.GetVersion() | SERIALIZE_TRANSACTION_NO_WITNESS);
+            SerializeToVector(os, non_witness_utxo);
+        } else if (!witness_utxo.IsNull()) {
+            SerializeToVector(s, PSBT_IN_WITNESS_UTXO);
+            SerializeToVector(s, witness_utxo);
+        }
+
+        if (final_script_sig.empty() && final_script_witness.IsNull()) {
+            // Write any partial signatures
+            for (auto sig_pair : partial_sigs) {
+                SerializeToVector(s, PSBT_IN_PARTIAL_SIG, MakeSpan(sig_pair.second.first));
+                s << sig_pair.second.second;
+            }
+
+            // Write the sighash type
+            if (sighash_type > 0) {
+                SerializeToVector(s, PSBT_IN_SIGHASH);
+                SerializeToVector(s, sighash_type);
+            }
+
+            // Write the redeem script
+            if (!redeem_script.empty()) {
+                SerializeToVector(s, PSBT_IN_REDEEMSCRIPT);
+                s << redeem_script;
+            }
+
+            // Write the witness script
+            if (!witness_script.empty()) {
+                SerializeToVector(s, PSBT_IN_WITNESSSCRIPT);
+                s << witness_script;
+            }
+
+            // Write any hd keypaths
+            SerializeHDKeypaths(s, hd_keypaths, PSBT_IN_BIP32_DERIVATION);
+        }
+
+        // Write script sig
+        if (!final_script_sig.empty()) {
+            SerializeToVector(s, PSBT_IN_SCRIPTSIG);
+            s << final_script_sig;
+        }
+        // write script witness
+        if (!final_script_witness.IsNull()) {
+            SerializeToVector(s, PSBT_IN_SCRIPTWITNESS);
+            SerializeToVector(s, final_script_witness.stack);
+        }
+
+        // Write unknown things
+        for (auto& entry : unknown) {
+            s << entry.first;
+            s << entry.second;
+        }
+
+        s << PSBT_SEPARATOR;
+    }
+
+
+    template <typename Stream>
+    inline void Unserialize(Stream& s) {
+        // Read loop
+        bool found_sep = false;
+        while(!s.empty()) {
+            // Read
+            std::vector<unsigned char> key;
+            s >> key;
+
+            // the key is empty if that was actually a separator byte
+            // This is a special case for key lengths 0 as those are not allowed (except for separator)
+            if (key.empty()) {
+                found_sep = true;
+                break;
+            }
+
+            // First byte of key is the type
+            unsigned char type = key[0];
+
+            // Do stuff based on type
+            switch(type) {
+                case PSBT_IN_NON_WITNESS_UTXO:
+                {
+                    if (non_witness_utxo) {
+                        throw std::ios_base::failure("Duplicate Key, input non-witness utxo already provided");
+                    } else if (key.size() != 1) {
+                        throw std::ios_base::failure("Non-witness utxo key is more than one byte type");
+                    }
+                    // Set the stream to unserialize with witness since this is always a valid network transaction
+                    OverrideStream<Stream> os(&s, s.GetType(), s.GetVersion() & ~SERIALIZE_TRANSACTION_NO_WITNESS);
+                    UnserializeFromVector(os, non_witness_utxo);
+                    break;
+                }
+                case PSBT_IN_WITNESS_UTXO:
+                    if (!witness_utxo.IsNull()) {
+                        throw std::ios_base::failure("Duplicate Key, input witness utxo already provided");
+                    } else if (key.size() != 1) {
+                        throw std::ios_base::failure("Witness utxo key is more than one byte type");
+                    }
+                    UnserializeFromVector(s, witness_utxo);
+                    break;
+                case PSBT_IN_PARTIAL_SIG:
+                {
+                    // Make sure that the key is the size of pubkey + 1
+                    if (key.size() != CPubKey::PUBLIC_KEY_SIZE + 1 && key.size() != CPubKey::COMPRESSED_PUBLIC_KEY_SIZE + 1) {
+                        throw std::ios_base::failure("Size of key was not the expected size for the type partial signature pubkey");
+                    }
+                    // Read in the pubkey from key
+                    CPubKey pubkey(key.begin() + 1, key.end());
+                    if (!pubkey.IsFullyValid()) {
+                       throw std::ios_base::failure("Invalid pubkey");
+                    }
+                    if (partial_sigs.count(pubkey.GetID()) > 0) {
+                        throw std::ios_base::failure("Duplicate Key, input partial signature for pubkey already provided");
+                    }
+
+                    // Read in the signature from value
+                    std::vector<unsigned char> sig;
+                    s >> sig;
+
+                    // Add to list
+                    partial_sigs.emplace(pubkey.GetID(), SigPair(pubkey, std::move(sig)));
+                    break;
+                }
+                case PSBT_IN_SIGHASH:
+                    if (sighash_type > 0) {
+                        throw std::ios_base::failure("Duplicate Key, input sighash type already provided");
+                    } else if (key.size() != 1) {
+                        throw std::ios_base::failure("Sighash type key is more than one byte type");
+                    }
+                    UnserializeFromVector(s, sighash_type);
+                    break;
+                case PSBT_IN_REDEEMSCRIPT:
+                {
+                    if (!redeem_script.empty()) {
+                        throw std::ios_base::failure("Duplicate Key, input redeemScript already provided");
+                    } else if (key.size() != 1) {
+                        throw std::ios_base::failure("Input redeemScript key is more than one byte type");
+                    }
+                    s >> redeem_script;
+                    break;
+                }
+                case PSBT_IN_WITNESSSCRIPT:
+                {
+                    if (!witness_script.empty()) {
+                        throw std::ios_base::failure("Duplicate Key, input witnessScript already provided");
+                    } else if (key.size() != 1) {
+                        throw std::ios_base::failure("Input witnessScript key is more than one byte type");
+                    }
+                    s >> witness_script;
+                    break;
+                }
+                case PSBT_IN_BIP32_DERIVATION:
+                {
+                    DeserializeHDKeypaths(s, key, hd_keypaths);
+                    break;
+                }
+                case PSBT_IN_SCRIPTSIG:
+                {
+                    if (!final_script_sig.empty()) {
+                        throw std::ios_base::failure("Duplicate Key, input final scriptSig already provided");
+                    } else if (key.size() != 1) {
+                        throw std::ios_base::failure("Final scriptSig key is more than one byte type");
+                    }
+                    s >> final_script_sig;
+                    break;
+                }
+                case PSBT_IN_SCRIPTWITNESS:
+                {
+                    if (!final_script_witness.IsNull()) {
+                        throw std::ios_base::failure("Duplicate Key, input final scriptWitness already provided");
+                    } else if (key.size() != 1) {
+                        throw std::ios_base::failure("Final scriptWitness key is more than one byte type");
+                    }
+                    UnserializeFromVector(s, final_script_witness.stack);
+                    break;
+                }
+                // Unknown stuff
+                default:
+                    if (unknown.count(key) > 0) {
+                        throw std::ios_base::failure("Duplicate Key, key for unknown value already provided");
+                    }
+                    // Read in the value
+                    std::vector<unsigned char> val_bytes;
+                    s >> val_bytes;
+                    unknown.emplace(std::move(key), std::move(val_bytes));
+                    break;
+            }
+        }
+
+        if (!found_sep) {
+            throw std::ios_base::failure("Separator is missing at the end of an input map");
+        }
+    }
+
+    template <typename Stream>
+    PSBTInput(deserialize_type, Stream& s) {
+        Unserialize(s);
+    }
+};
+
+/** A structure for PSBTs which contains per output information */
+struct PSBTOutput
+{
+    CScript redeem_script;
+    CScript witness_script;
+    std::map<CPubKey, KeyOriginInfo> hd_keypaths;
+    std::map<std::vector<unsigned char>, std::vector<unsigned char>> unknown;
+
+    bool IsNull() const;
+    void FillSignatureData(SignatureData& sigdata) const;
+    void FromSignatureData(const SignatureData& sigdata);
+    void Merge(const PSBTOutput& output);
+    bool IsSane() const;
+    PSBTOutput() {}
+
+    template <typename Stream>
+    inline void Serialize(Stream& s) const {
+        // Write the redeem script
+        if (!redeem_script.empty()) {
+            SerializeToVector(s, PSBT_OUT_REDEEMSCRIPT);
+            s << redeem_script;
+        }
+
+        // Write the witness script
+        if (!witness_script.empty()) {
+            SerializeToVector(s, PSBT_OUT_WITNESSSCRIPT);
+            s << witness_script;
+        }
+
+        // Write any hd keypaths
+        SerializeHDKeypaths(s, hd_keypaths, PSBT_OUT_BIP32_DERIVATION);
+
+        // Write unknown things
+        for (auto& entry : unknown) {
+            s << entry.first;
+            s << entry.second;
+        }
+
+        s << PSBT_SEPARATOR;
+    }
+
+
+    template <typename Stream>
+    inline void Unserialize(Stream& s) {
+        // Read loop
+        bool found_sep = false;
+        while(!s.empty()) {
+            // Read
+            std::vector<unsigned char> key;
+            s >> key;
+
+            // the key is empty if that was actually a separator byte
+            // This is a special case for key lengths 0 as those are not allowed (except for separator)
+            if (key.empty()) {
+                found_sep = true;
+                break;
+            }
+
+            // First byte of key is the type
+            unsigned char type = key[0];
+
+            // Do stuff based on type
+            switch(type) {
+                case PSBT_OUT_REDEEMSCRIPT:
+                {
+                    if (!redeem_script.empty()) {
+                        throw std::ios_base::failure("Duplicate Key, output redeemScript already provided");
+                    } else if (key.size() != 1) {
+                        throw std::ios_base::failure("Output redeemScript key is more than one byte type");
+                    }
+                    s >> redeem_script;
+                    break;
+                }
+                case PSBT_OUT_WITNESSSCRIPT:
+                {
+                    if (!witness_script.empty()) {
+                        throw std::ios_base::failure("Duplicate Key, output witnessScript already provided");
+                    } else if (key.size() != 1) {
+                        throw std::ios_base::failure("Output witnessScript key is more than one byte type");
+                    }
+                    s >> witness_script;
+                    break;
+                }
+                case PSBT_OUT_BIP32_DERIVATION:
+                {
+                    DeserializeHDKeypaths(s, key, hd_keypaths);
+                    break;
+                }
+                // Unknown stuff
+                default: {
+                    if (unknown.count(key) > 0) {
+                        throw std::ios_base::failure("Duplicate Key, key for unknown value already provided");
+                    }
+                    // Read in the value
+                    std::vector<unsigned char> val_bytes;
+                    s >> val_bytes;
+                    unknown.emplace(std::move(key), std::move(val_bytes));
+                    break;
+                }
+            }
+        }
+
+        if (!found_sep) {
+            throw std::ios_base::failure("Separator is missing at the end of an output map");
+        }
+    }
+
+    template <typename Stream>
+    PSBTOutput(deserialize_type, Stream& s) {
+        Unserialize(s);
+    }
+};
+
+/** A version of CTransaction with the PSBT format*/
+struct PartiallySignedTransaction
+{
+    boost::optional<CMutableTransaction> tx;
+    std::vector<PSBTInput> inputs;
+    std::vector<PSBTOutput> outputs;
+    std::map<std::vector<unsigned char>, std::vector<unsigned char>> unknown;
+
+    bool IsNull() const;
+    void Merge(const PartiallySignedTransaction& psbt);
+    bool IsSane() const;
+    PartiallySignedTransaction() {}
+    PartiallySignedTransaction(const PartiallySignedTransaction& psbt_in) : tx(psbt_in.tx), inputs(psbt_in.inputs), outputs(psbt_in.outputs), unknown(psbt_in.unknown) {}
+    explicit PartiallySignedTransaction(const CMutableTransaction& tx);
+
+    // Only checks if they refer to the same transaction
+    friend bool operator==(const PartiallySignedTransaction& a, const PartiallySignedTransaction &b)
+    {
+        return a.tx->GetHash() == b.tx->GetHash();
+    }
+    friend bool operator!=(const PartiallySignedTransaction& a, const PartiallySignedTransaction &b)
+    {
+        return !(a == b);
+    }
+
+    template <typename Stream>
+    inline void Serialize(Stream& s) const {
+
+        // magic bytes
+        s << PSBT_MAGIC_BYTES;
+
+        // unsigned tx flag
+        SerializeToVector(s, PSBT_GLOBAL_UNSIGNED_TX);
+
+        // Write serialized tx to a stream
+        OverrideStream<Stream> os(&s, s.GetType(), s.GetVersion() | SERIALIZE_TRANSACTION_NO_WITNESS);
+        SerializeToVector(os, *tx);
+
+        // Write the unknown things
+        for (auto& entry : unknown) {
+            s << entry.first;
+            s << entry.second;
+        }
+
+        // Separator
+        s << PSBT_SEPARATOR;
+
+        // Write inputs
+        for (const PSBTInput& input : inputs) {
+            s << input;
+        }
+        // Write outputs
+        for (const PSBTOutput& output : outputs) {
+            s << output;
+        }
+    }
+
+
+    template <typename Stream>
+    inline void Unserialize(Stream& s) {
+        // Read the magic bytes
+        uint8_t magic[5];
+        s >> magic;
+        if (!std::equal(magic, magic + 5, PSBT_MAGIC_BYTES)) {
+            throw std::ios_base::failure("Invalid PSBT magic bytes");
+        }
+
+        // Read global data
+        bool found_sep = false;
+        while(!s.empty()) {
+            // Read
+            std::vector<unsigned char> key;
+            s >> key;
+
+            // the key is empty if that was actually a separator byte
+            // This is a special case for key lengths 0 as those are not allowed (except for separator)
+            if (key.empty()) {
+                found_sep = true;
+                break;
+            }
+
+            // First byte of key is the type
+            unsigned char type = key[0];
+
+            // Do stuff based on type
+            switch(type) {
+                case PSBT_GLOBAL_UNSIGNED_TX:
+                {
+                    if (tx) {
+                        throw std::ios_base::failure("Duplicate Key, unsigned tx already provided");
+                    } else if (key.size() != 1) {
+                        throw std::ios_base::failure("Global unsigned tx key is more than one byte type");
+                    }
+                    CMutableTransaction mtx;
+                    // Set the stream to serialize with non-witness since this should always be non-witness
+                    OverrideStream<Stream> os(&s, s.GetType(), s.GetVersion() | SERIALIZE_TRANSACTION_NO_WITNESS);
+                    UnserializeFromVector(os, mtx);
+                    tx = std::move(mtx);
+                    // Make sure that all scriptSigs and scriptWitnesses are empty
+                    for (const CTxIn& txin : tx->vin) {
+                        if (!txin.scriptSig.empty() || !txin.scriptWitness.IsNull()) {
+                            throw std::ios_base::failure("Unsigned tx does not have empty scriptSigs and scriptWitnesses.");
+                        }
+                    }
+                    break;
+                }
+                // Unknown stuff
+                default: {
+                    if (unknown.count(key) > 0) {
+                        throw std::ios_base::failure("Duplicate Key, key for unknown value already provided");
+                    }
+                    // Read in the value
+                    std::vector<unsigned char> val_bytes;
+                    s >> val_bytes;
+                    unknown.emplace(std::move(key), std::move(val_bytes));
+                }
+            }
+        }
+
+        if (!found_sep) {
+            throw std::ios_base::failure("Separator is missing at the end of the global map");
+        }
+
+        // Make sure that we got an unsigned tx
+        if (!tx) {
+            throw std::ios_base::failure("No unsigned transcation was provided");
+        }
+
+        // Read input data
+        unsigned int i = 0;
+        while (!s.empty() && i < tx->vin.size()) {
+            PSBTInput input;
+            s >> input;
+            inputs.push_back(input);
+
+            // Make sure the non-witness utxo matches the outpoint
+            if (input.non_witness_utxo && input.non_witness_utxo->GetHash() != tx->vin[i].prevout.hash) {
+                throw std::ios_base::failure("Non-witness UTXO does not match outpoint hash");
+            }
+            ++i;
+        }
+        // Make sure that the number of inputs matches the number of inputs in the transaction
+        if (inputs.size() != tx->vin.size()) {
+            throw std::ios_base::failure("Inputs provided does not match the number of inputs in transaction.");
+        }
+
+        // Read output data
+        i = 0;
+        while (!s.empty() && i < tx->vout.size()) {
+            PSBTOutput output;
+            s >> output;
+            outputs.push_back(output);
+            ++i;
+        }
+        // Make sure that the number of outputs matches the number of outputs in the transaction
+        if (outputs.size() != tx->vout.size()) {
+            throw std::ios_base::failure("Outputs provided does not match the number of outputs in transaction.");
+        }
+        // Sanity check
+        if (!IsSane()) {
+            throw std::ios_base::failure("PSBT is not sane.");
+        }
+    }
+
+    template <typename Stream>
+    PartiallySignedTransaction(deserialize_type, Stream& s) {
+        Unserialize(s);
+    }
+};
+
+/** Checks whether a PSBTInput is already signed. */
+bool PSBTInputSigned(PSBTInput& input);
+
+/** Signs a PSBTInput, verifying that all provided data matches what is being signed. */
+bool SignPSBTInput(const SigningProvider& provider, PartiallySignedTransaction& psbt, int index, int sighash = SIGHASH_ALL);
+
+#endif // BITCOIN_PSBT_H
diff --git a/src/rpc/rawtransaction.cpp b/src/rpc/rawtransaction.cpp
index 8e561c6184..03e38739a1 100644
--- a/src/rpc/rawtransaction.cpp
+++ b/src/rpc/rawtransaction.cpp
@@ -17,6 +17,7 @@
 #include <policy/policy.h>
 #include <policy/rbf.h>
 #include <primitives/transaction.h>
+#include <psbt.h>
 #include <rpc/rawtransaction.h>
 #include <rpc/server.h>
 #include <rpc/util.h>
diff --git a/src/script/sign.cpp b/src/script/sign.cpp
index 792fb2997f..9d6a390ea2 100644
--- a/src/script/sign.cpp
+++ b/src/script/sign.cpp
@@ -232,67 +232,6 @@ bool ProduceSignature(const SigningProvider& provider, const BaseSignatureCreato
     return sigdata.complete;
 }
 
-bool PSBTInputSigned(PSBTInput& input)
-{
-    return !input.final_script_sig.empty() || !input.final_script_witness.IsNull();
-}
-
-bool SignPSBTInput(const SigningProvider& provider, PartiallySignedTransaction& psbt, int index, int sighash)
-{
-    PSBTInput& input = psbt.inputs.at(index);
-    const CMutableTransaction& tx = *psbt.tx;
-
-    if (PSBTInputSigned(input)) {
-        return true;
-    }
-
-    // Fill SignatureData with input info
-    SignatureData sigdata;
-    input.FillSignatureData(sigdata);
-
-    // Get UTXO
-    bool require_witness_sig = false;
-    CTxOut utxo;
-
-    // Verify input sanity, which checks that at most one of witness or non-witness utxos is provided.
-    if (!input.IsSane()) {
-        return false;
-    }
-
-    if (input.non_witness_utxo) {
-        // If we're taking our information from a non-witness UTXO, verify that it matches the prevout.
-        COutPoint prevout = tx.vin[index].prevout;
-        if (input.non_witness_utxo->GetHash() != prevout.hash) {
-            return false;
-        }
-        utxo = input.non_witness_utxo->vout[prevout.n];
-    } else if (!input.witness_utxo.IsNull()) {
-        utxo = input.witness_utxo;
-        // When we're taking our information from a witness UTXO, we can't verify it is actually data from
-        // the output being spent. This is safe in case a witness signature is produced (which includes this
-        // information directly in the hash), but not for non-witness signatures. Remember that we require
-        // a witness signature in this situation.
-        require_witness_sig = true;
-    } else {
-        return false;
-    }
-
-    MutableTransactionSignatureCreator creator(&tx, index, utxo.nValue, sighash);
-    sigdata.witness = false;
-    bool sig_complete = ProduceSignature(provider, creator, utxo.scriptPubKey, sigdata);
-    // Verify that a witness signature was produced in case one was required.
-    if (require_witness_sig && !sigdata.witness) return false;
-    input.FromSignatureData(sigdata);
-
-    // If we have a witness signature, use the smaller witness UTXO.
-    if (sigdata.witness) {
-        input.witness_utxo = utxo;
-        input.non_witness_utxo = nullptr;
-    }
-
-    return sig_complete;
-}
-
 class SignatureExtractorChecker final : public BaseSignatureChecker
 {
 private:
@@ -509,166 +448,6 @@ bool IsSolvable(const SigningProvider& provider, const CScript& script)
     return false;
 }
 
-PartiallySignedTransaction::PartiallySignedTransaction(const CMutableTransaction& tx) : tx(tx)
-{
-    inputs.resize(tx.vin.size());
-    outputs.resize(tx.vout.size());
-}
-
-bool PartiallySignedTransaction::IsNull() const
-{
-    return !tx && inputs.empty() && outputs.empty() && unknown.empty();
-}
-
-void PartiallySignedTransaction::Merge(const PartiallySignedTransaction& psbt)
-{
-    for (unsigned int i = 0; i < inputs.size(); ++i) {
-        inputs[i].Merge(psbt.inputs[i]);
-    }
-    for (unsigned int i = 0; i < outputs.size(); ++i) {
-        outputs[i].Merge(psbt.outputs[i]);
-    }
-    unknown.insert(psbt.unknown.begin(), psbt.unknown.end());
-}
-
-bool PartiallySignedTransaction::IsSane() const
-{
-    for (PSBTInput input : inputs) {
-        if (!input.IsSane()) return false;
-    }
-    return true;
-}
-
-bool PSBTInput::IsNull() const
-{
-    return !non_witness_utxo && witness_utxo.IsNull() && partial_sigs.empty() && unknown.empty() && hd_keypaths.empty() && redeem_script.empty() && witness_script.empty();
-}
-
-void PSBTInput::FillSignatureData(SignatureData& sigdata) const
-{
-    if (!final_script_sig.empty()) {
-        sigdata.scriptSig = final_script_sig;
-        sigdata.complete = true;
-    }
-    if (!final_script_witness.IsNull()) {
-        sigdata.scriptWitness = final_script_witness;
-        sigdata.complete = true;
-    }
-    if (sigdata.complete) {
-        return;
-    }
-
-    sigdata.signatures.insert(partial_sigs.begin(), partial_sigs.end());
-    if (!redeem_script.empty()) {
-        sigdata.redeem_script = redeem_script;
-    }
-    if (!witness_script.empty()) {
-        sigdata.witness_script = witness_script;
-    }
-    for (const auto& key_pair : hd_keypaths) {
-        sigdata.misc_pubkeys.emplace(key_pair.first.GetID(), key_pair);
-    }
-}
-
-void PSBTInput::FromSignatureData(const SignatureData& sigdata)
-{
-    if (sigdata.complete) {
-        partial_sigs.clear();
-        hd_keypaths.clear();
-        redeem_script.clear();
-        witness_script.clear();
-
-        if (!sigdata.scriptSig.empty()) {
-            final_script_sig = sigdata.scriptSig;
-        }
-        if (!sigdata.scriptWitness.IsNull()) {
-            final_script_witness = sigdata.scriptWitness;
-        }
-        return;
-    }
-
-    partial_sigs.insert(sigdata.signatures.begin(), sigdata.signatures.end());
-    if (redeem_script.empty() && !sigdata.redeem_script.empty()) {
-        redeem_script = sigdata.redeem_script;
-    }
-    if (witness_script.empty() && !sigdata.witness_script.empty()) {
-        witness_script = sigdata.witness_script;
-    }
-    for (const auto& entry : sigdata.misc_pubkeys) {
-        hd_keypaths.emplace(entry.second);
-    }
-}
-
-void PSBTInput::Merge(const PSBTInput& input)
-{
-    if (!non_witness_utxo && input.non_witness_utxo) non_witness_utxo = input.non_witness_utxo;
-    if (witness_utxo.IsNull() && !input.witness_utxo.IsNull()) {
-        witness_utxo = input.witness_utxo;
-        non_witness_utxo = nullptr; // Clear out any non-witness utxo when we set a witness one.
-    }
-
-    partial_sigs.insert(input.partial_sigs.begin(), input.partial_sigs.end());
-    hd_keypaths.insert(input.hd_keypaths.begin(), input.hd_keypaths.end());
-    unknown.insert(input.unknown.begin(), input.unknown.end());
-
-    if (redeem_script.empty() && !input.redeem_script.empty()) redeem_script = input.redeem_script;
-    if (witness_script.empty() && !input.witness_script.empty()) witness_script = input.witness_script;
-    if (final_script_sig.empty() && !input.final_script_sig.empty()) final_script_sig = input.final_script_sig;
-    if (final_script_witness.IsNull() && !input.final_script_witness.IsNull()) final_script_witness = input.final_script_witness;
-}
-
-bool PSBTInput::IsSane() const
-{
-    // Cannot have both witness and non-witness utxos
-    if (!witness_utxo.IsNull() && non_witness_utxo) return false;
-
-    // If we have a witness_script or a scriptWitness, we must also have a witness utxo
-    if (!witness_script.empty() && witness_utxo.IsNull()) return false;
-    if (!final_script_witness.IsNull() && witness_utxo.IsNull()) return false;
-
-    return true;
-}
-
-void PSBTOutput::FillSignatureData(SignatureData& sigdata) const
-{
-    if (!redeem_script.empty()) {
-        sigdata.redeem_script = redeem_script;
-    }
-    if (!witness_script.empty()) {
-        sigdata.witness_script = witness_script;
-    }
-    for (const auto& key_pair : hd_keypaths) {
-        sigdata.misc_pubkeys.emplace(key_pair.first.GetID(), key_pair);
-    }
-}
-
-void PSBTOutput::FromSignatureData(const SignatureData& sigdata)
-{
-    if (redeem_script.empty() && !sigdata.redeem_script.empty()) {
-        redeem_script = sigdata.redeem_script;
-    }
-    if (witness_script.empty() && !sigdata.witness_script.empty()) {
-        witness_script = sigdata.witness_script;
-    }
-    for (const auto& entry : sigdata.misc_pubkeys) {
-        hd_keypaths.emplace(entry.second);
-    }
-}
-
-bool PSBTOutput::IsNull() const
-{
-    return redeem_script.empty() && witness_script.empty() && hd_keypaths.empty() && unknown.empty();
-}
-
-void PSBTOutput::Merge(const PSBTOutput& output)
-{
-    hd_keypaths.insert(output.hd_keypaths.begin(), output.hd_keypaths.end());
-    unknown.insert(output.unknown.begin(), output.unknown.end());
-
-    if (redeem_script.empty() && !output.redeem_script.empty()) redeem_script = output.redeem_script;
-    if (witness_script.empty() && !output.witness_script.empty()) witness_script = output.witness_script;
-}
-
 bool HidingSigningProvider::GetCScript(const CScriptID& scriptid, CScript& script) const
 {
     return m_provider->GetCScript(scriptid, script);
diff --git a/src/script/sign.h b/src/script/sign.h
index e884f4c480..64eb3eb8e5 100644
--- a/src/script/sign.h
+++ b/src/script/sign.h
@@ -123,32 +123,6 @@ struct SignatureData {
     void MergeSignatureData(SignatureData sigdata);
 };
 
-// Magic bytes
-static constexpr uint8_t PSBT_MAGIC_BYTES[5] = {'p', 's', 'b', 't', 0xff};
-
-// Global types
-static constexpr uint8_t PSBT_GLOBAL_UNSIGNED_TX = 0x00;
-
-// Input types
-static constexpr uint8_t PSBT_IN_NON_WITNESS_UTXO = 0x00;
-static constexpr uint8_t PSBT_IN_WITNESS_UTXO = 0x01;
-static constexpr uint8_t PSBT_IN_PARTIAL_SIG = 0x02;
-static constexpr uint8_t PSBT_IN_SIGHASH = 0x03;
-static constexpr uint8_t PSBT_IN_REDEEMSCRIPT = 0x04;
-static constexpr uint8_t PSBT_IN_WITNESSSCRIPT = 0x05;
-static constexpr uint8_t PSBT_IN_BIP32_DERIVATION = 0x06;
-static constexpr uint8_t PSBT_IN_SCRIPTSIG = 0x07;
-static constexpr uint8_t PSBT_IN_SCRIPTWITNESS = 0x08;
-
-// Output types
-static constexpr uint8_t PSBT_OUT_REDEEMSCRIPT = 0x00;
-static constexpr uint8_t PSBT_OUT_WITNESSSCRIPT = 0x01;
-static constexpr uint8_t PSBT_OUT_BIP32_DERIVATION = 0x02;
-
-// The separator is 0x00. Reading this in means that the unserializer can interpret it
-// as a 0 length key which indicates that this is the separator. The separator has no value.
-static constexpr uint8_t PSBT_SEPARATOR = 0x00;
-
 // Takes a stream and multiple arguments and serializes them as if first serialized into a vector and then into the stream
 // The resulting output into the stream has the total serialized length of all of the objects followed by all objects concatenated with each other.
 template<typename Stream, typename... X>
@@ -223,514 +197,6 @@ void SerializeHDKeypaths(Stream& s, const std::map<CPubKey, KeyOriginInfo>& hd_k
     }
 }
 
-/** A structure for PSBTs which contain per-input information */
-struct PSBTInput
-{
-    CTransactionRef non_witness_utxo;
-    CTxOut witness_utxo;
-    CScript redeem_script;
-    CScript witness_script;
-    CScript final_script_sig;
-    CScriptWitness final_script_witness;
-    std::map<CPubKey, KeyOriginInfo> hd_keypaths;
-    std::map<CKeyID, SigPair> partial_sigs;
-    std::map<std::vector<unsigned char>, std::vector<unsigned char>> unknown;
-    int sighash_type = 0;
-
-    bool IsNull() const;
-    void FillSignatureData(SignatureData& sigdata) const;
-    void FromSignatureData(const SignatureData& sigdata);
-    void Merge(const PSBTInput& input);
-    bool IsSane() const;
-    PSBTInput() {}
-
-    template <typename Stream>
-    inline void Serialize(Stream& s) const {
-        // Write the utxo
-        // If there is a non-witness utxo, then don't add the witness one.
-        if (non_witness_utxo) {
-            SerializeToVector(s, PSBT_IN_NON_WITNESS_UTXO);
-            OverrideStream<Stream> os(&s, s.GetType(), s.GetVersion() | SERIALIZE_TRANSACTION_NO_WITNESS);
-            SerializeToVector(os, non_witness_utxo);
-        } else if (!witness_utxo.IsNull()) {
-            SerializeToVector(s, PSBT_IN_WITNESS_UTXO);
-            SerializeToVector(s, witness_utxo);
-        }
-
-        if (final_script_sig.empty() && final_script_witness.IsNull()) {
-            // Write any partial signatures
-            for (auto sig_pair : partial_sigs) {
-                SerializeToVector(s, PSBT_IN_PARTIAL_SIG, MakeSpan(sig_pair.second.first));
-                s << sig_pair.second.second;
-            }
-
-            // Write the sighash type
-            if (sighash_type > 0) {
-                SerializeToVector(s, PSBT_IN_SIGHASH);
-                SerializeToVector(s, sighash_type);
-            }
-
-            // Write the redeem script
-            if (!redeem_script.empty()) {
-                SerializeToVector(s, PSBT_IN_REDEEMSCRIPT);
-                s << redeem_script;
-            }
-
-            // Write the witness script
-            if (!witness_script.empty()) {
-                SerializeToVector(s, PSBT_IN_WITNESSSCRIPT);
-                s << witness_script;
-            }
-
-            // Write any hd keypaths
-            SerializeHDKeypaths(s, hd_keypaths, PSBT_IN_BIP32_DERIVATION);
-        }
-
-        // Write script sig
-        if (!final_script_sig.empty()) {
-            SerializeToVector(s, PSBT_IN_SCRIPTSIG);
-            s << final_script_sig;
-        }
-        // write script witness
-        if (!final_script_witness.IsNull()) {
-            SerializeToVector(s, PSBT_IN_SCRIPTWITNESS);
-            SerializeToVector(s, final_script_witness.stack);
-        }
-
-        // Write unknown things
-        for (auto& entry : unknown) {
-            s << entry.first;
-            s << entry.second;
-        }
-
-        s << PSBT_SEPARATOR;
-    }
-
-
-    template <typename Stream>
-    inline void Unserialize(Stream& s) {
-        // Read loop
-        bool found_sep = false;
-        while(!s.empty()) {
-            // Read
-            std::vector<unsigned char> key;
-            s >> key;
-
-            // the key is empty if that was actually a separator byte
-            // This is a special case for key lengths 0 as those are not allowed (except for separator)
-            if (key.empty()) {
-                found_sep = true;
-                break;
-            }
-
-            // First byte of key is the type
-            unsigned char type = key[0];
-
-            // Do stuff based on type
-            switch(type) {
-                case PSBT_IN_NON_WITNESS_UTXO:
-                {
-                    if (non_witness_utxo) {
-                        throw std::ios_base::failure("Duplicate Key, input non-witness utxo already provided");
-                    } else if (key.size() != 1) {
-                        throw std::ios_base::failure("Non-witness utxo key is more than one byte type");
-                    }
-                    // Set the stream to unserialize with witness since this is always a valid network transaction
-                    OverrideStream<Stream> os(&s, s.GetType(), s.GetVersion() & ~SERIALIZE_TRANSACTION_NO_WITNESS);
-                    UnserializeFromVector(os, non_witness_utxo);
-                    break;
-                }
-                case PSBT_IN_WITNESS_UTXO:
-                    if (!witness_utxo.IsNull()) {
-                        throw std::ios_base::failure("Duplicate Key, input witness utxo already provided");
-                    } else if (key.size() != 1) {
-                        throw std::ios_base::failure("Witness utxo key is more than one byte type");
-                    }
-                    UnserializeFromVector(s, witness_utxo);
-                    break;
-                case PSBT_IN_PARTIAL_SIG:
-                {
-                    // Make sure that the key is the size of pubkey + 1
-                    if (key.size() != CPubKey::PUBLIC_KEY_SIZE + 1 && key.size() != CPubKey::COMPRESSED_PUBLIC_KEY_SIZE + 1) {
-                        throw std::ios_base::failure("Size of key was not the expected size for the type partial signature pubkey");
-                    }
-                    // Read in the pubkey from key
-                    CPubKey pubkey(key.begin() + 1, key.end());
-                    if (!pubkey.IsFullyValid()) {
-                       throw std::ios_base::failure("Invalid pubkey");
-                    }
-                    if (partial_sigs.count(pubkey.GetID()) > 0) {
-                        throw std::ios_base::failure("Duplicate Key, input partial signature for pubkey already provided");
-                    }
-
-                    // Read in the signature from value
-                    std::vector<unsigned char> sig;
-                    s >> sig;
-
-                    // Add to list
-                    partial_sigs.emplace(pubkey.GetID(), SigPair(pubkey, std::move(sig)));
-                    break;
-                }
-                case PSBT_IN_SIGHASH:
-                    if (sighash_type > 0) {
-                        throw std::ios_base::failure("Duplicate Key, input sighash type already provided");
-                    } else if (key.size() != 1) {
-                        throw std::ios_base::failure("Sighash type key is more than one byte type");
-                    }
-                    UnserializeFromVector(s, sighash_type);
-                    break;
-                case PSBT_IN_REDEEMSCRIPT:
-                {
-                    if (!redeem_script.empty()) {
-                        throw std::ios_base::failure("Duplicate Key, input redeemScript already provided");
-                    } else if (key.size() != 1) {
-                        throw std::ios_base::failure("Input redeemScript key is more than one byte type");
-                    }
-                    s >> redeem_script;
-                    break;
-                }
-                case PSBT_IN_WITNESSSCRIPT:
-                {
-                    if (!witness_script.empty()) {
-                        throw std::ios_base::failure("Duplicate Key, input witnessScript already provided");
-                    } else if (key.size() != 1) {
-                        throw std::ios_base::failure("Input witnessScript key is more than one byte type");
-                    }
-                    s >> witness_script;
-                    break;
-                }
-                case PSBT_IN_BIP32_DERIVATION:
-                {
-                    DeserializeHDKeypaths(s, key, hd_keypaths);
-                    break;
-                }
-                case PSBT_IN_SCRIPTSIG:
-                {
-                    if (!final_script_sig.empty()) {
-                        throw std::ios_base::failure("Duplicate Key, input final scriptSig already provided");
-                    } else if (key.size() != 1) {
-                        throw std::ios_base::failure("Final scriptSig key is more than one byte type");
-                    }
-                    s >> final_script_sig;
-                    break;
-                }
-                case PSBT_IN_SCRIPTWITNESS:
-                {
-                    if (!final_script_witness.IsNull()) {
-                        throw std::ios_base::failure("Duplicate Key, input final scriptWitness already provided");
-                    } else if (key.size() != 1) {
-                        throw std::ios_base::failure("Final scriptWitness key is more than one byte type");
-                    }
-                    UnserializeFromVector(s, final_script_witness.stack);
-                    break;
-                }
-                // Unknown stuff
-                default:
-                    if (unknown.count(key) > 0) {
-                        throw std::ios_base::failure("Duplicate Key, key for unknown value already provided");
-                    }
-                    // Read in the value
-                    std::vector<unsigned char> val_bytes;
-                    s >> val_bytes;
-                    unknown.emplace(std::move(key), std::move(val_bytes));
-                    break;
-            }
-        }
-
-        if (!found_sep) {
-            throw std::ios_base::failure("Separator is missing at the end of an input map");
-        }
-    }
-
-    template <typename Stream>
-    PSBTInput(deserialize_type, Stream& s) {
-        Unserialize(s);
-    }
-};
-
-/** A structure for PSBTs which contains per output information */
-struct PSBTOutput
-{
-    CScript redeem_script;
-    CScript witness_script;
-    std::map<CPubKey, KeyOriginInfo> hd_keypaths;
-    std::map<std::vector<unsigned char>, std::vector<unsigned char>> unknown;
-
-    bool IsNull() const;
-    void FillSignatureData(SignatureData& sigdata) const;
-    void FromSignatureData(const SignatureData& sigdata);
-    void Merge(const PSBTOutput& output);
-    bool IsSane() const;
-    PSBTOutput() {}
-
-    template <typename Stream>
-    inline void Serialize(Stream& s) const {
-        // Write the redeem script
-        if (!redeem_script.empty()) {
-            SerializeToVector(s, PSBT_OUT_REDEEMSCRIPT);
-            s << redeem_script;
-        }
-
-        // Write the witness script
-        if (!witness_script.empty()) {
-            SerializeToVector(s, PSBT_OUT_WITNESSSCRIPT);
-            s << witness_script;
-        }
-
-        // Write any hd keypaths
-        SerializeHDKeypaths(s, hd_keypaths, PSBT_OUT_BIP32_DERIVATION);
-
-        // Write unknown things
-        for (auto& entry : unknown) {
-            s << entry.first;
-            s << entry.second;
-        }
-
-        s << PSBT_SEPARATOR;
-    }
-
-
-    template <typename Stream>
-    inline void Unserialize(Stream& s) {
-        // Read loop
-        bool found_sep = false;
-        while(!s.empty()) {
-            // Read
-            std::vector<unsigned char> key;
-            s >> key;
-
-            // the key is empty if that was actually a separator byte
-            // This is a special case for key lengths 0 as those are not allowed (except for separator)
-            if (key.empty()) {
-                found_sep = true;
-                break;
-            }
-
-            // First byte of key is the type
-            unsigned char type = key[0];
-
-            // Do stuff based on type
-            switch(type) {
-                case PSBT_OUT_REDEEMSCRIPT:
-                {
-                    if (!redeem_script.empty()) {
-                        throw std::ios_base::failure("Duplicate Key, output redeemScript already provided");
-                    } else if (key.size() != 1) {
-                        throw std::ios_base::failure("Output redeemScript key is more than one byte type");
-                    }
-                    s >> redeem_script;
-                    break;
-                }
-                case PSBT_OUT_WITNESSSCRIPT:
-                {
-                    if (!witness_script.empty()) {
-                        throw std::ios_base::failure("Duplicate Key, output witnessScript already provided");
-                    } else if (key.size() != 1) {
-                        throw std::ios_base::failure("Output witnessScript key is more than one byte type");
-                    }
-                    s >> witness_script;
-                    break;
-                }
-                case PSBT_OUT_BIP32_DERIVATION:
-                {
-                    DeserializeHDKeypaths(s, key, hd_keypaths);
-                    break;
-                }
-                // Unknown stuff
-                default: {
-                    if (unknown.count(key) > 0) {
-                        throw std::ios_base::failure("Duplicate Key, key for unknown value already provided");
-                    }
-                    // Read in the value
-                    std::vector<unsigned char> val_bytes;
-                    s >> val_bytes;
-                    unknown.emplace(std::move(key), std::move(val_bytes));
-                    break;
-                }
-            }
-        }
-
-        if (!found_sep) {
-            throw std::ios_base::failure("Separator is missing at the end of an output map");
-        }
-    }
-
-    template <typename Stream>
-    PSBTOutput(deserialize_type, Stream& s) {
-        Unserialize(s);
-    }
-};
-
-/** A version of CTransaction with the PSBT format*/
-struct PartiallySignedTransaction
-{
-    boost::optional<CMutableTransaction> tx;
-    std::vector<PSBTInput> inputs;
-    std::vector<PSBTOutput> outputs;
-    std::map<std::vector<unsigned char>, std::vector<unsigned char>> unknown;
-
-    bool IsNull() const;
-    void Merge(const PartiallySignedTransaction& psbt);
-    bool IsSane() const;
-    PartiallySignedTransaction() {}
-    PartiallySignedTransaction(const PartiallySignedTransaction& psbt_in) : tx(psbt_in.tx), inputs(psbt_in.inputs), outputs(psbt_in.outputs), unknown(psbt_in.unknown) {}
-    explicit PartiallySignedTransaction(const CMutableTransaction& tx);
-
-    // Only checks if they refer to the same transaction
-    friend bool operator==(const PartiallySignedTransaction& a, const PartiallySignedTransaction &b)
-    {
-        return a.tx->GetHash() == b.tx->GetHash();
-    }
-    friend bool operator!=(const PartiallySignedTransaction& a, const PartiallySignedTransaction &b)
-    {
-        return !(a == b);
-    }
-
-    template <typename Stream>
-    inline void Serialize(Stream& s) const {
-
-        // magic bytes
-        s << PSBT_MAGIC_BYTES;
-
-        // unsigned tx flag
-        SerializeToVector(s, PSBT_GLOBAL_UNSIGNED_TX);
-
-        // Write serialized tx to a stream
-        OverrideStream<Stream> os(&s, s.GetType(), s.GetVersion() | SERIALIZE_TRANSACTION_NO_WITNESS);
-        SerializeToVector(os, *tx);
-
-        // Write the unknown things
-        for (auto& entry : unknown) {
-            s << entry.first;
-            s << entry.second;
-        }
-
-        // Separator
-        s << PSBT_SEPARATOR;
-
-        // Write inputs
-        for (const PSBTInput& input : inputs) {
-            s << input;
-        }
-        // Write outputs
-        for (const PSBTOutput& output : outputs) {
-            s << output;
-        }
-    }
-
-
-    template <typename Stream>
-    inline void Unserialize(Stream& s) {
-        // Read the magic bytes
-        uint8_t magic[5];
-        s >> magic;
-        if (!std::equal(magic, magic + 5, PSBT_MAGIC_BYTES)) {
-            throw std::ios_base::failure("Invalid PSBT magic bytes");
-        }
-
-        // Read global data
-        bool found_sep = false;
-        while(!s.empty()) {
-            // Read
-            std::vector<unsigned char> key;
-            s >> key;
-
-            // the key is empty if that was actually a separator byte
-            // This is a special case for key lengths 0 as those are not allowed (except for separator)
-            if (key.empty()) {
-                found_sep = true;
-                break;
-            }
-
-            // First byte of key is the type
-            unsigned char type = key[0];
-
-            // Do stuff based on type
-            switch(type) {
-                case PSBT_GLOBAL_UNSIGNED_TX:
-                {
-                    if (tx) {
-                        throw std::ios_base::failure("Duplicate Key, unsigned tx already provided");
-                    } else if (key.size() != 1) {
-                        throw std::ios_base::failure("Global unsigned tx key is more than one byte type");
-                    }
-                    CMutableTransaction mtx;
-                    // Set the stream to serialize with non-witness since this should always be non-witness
-                    OverrideStream<Stream> os(&s, s.GetType(), s.GetVersion() | SERIALIZE_TRANSACTION_NO_WITNESS);
-                    UnserializeFromVector(os, mtx);
-                    tx = std::move(mtx);
-                    // Make sure that all scriptSigs and scriptWitnesses are empty
-                    for (const CTxIn& txin : tx->vin) {
-                        if (!txin.scriptSig.empty() || !txin.scriptWitness.IsNull()) {
-                            throw std::ios_base::failure("Unsigned tx does not have empty scriptSigs and scriptWitnesses.");
-                        }
-                    }
-                    break;
-                }
-                // Unknown stuff
-                default: {
-                    if (unknown.count(key) > 0) {
-                        throw std::ios_base::failure("Duplicate Key, key for unknown value already provided");
-                    }
-                    // Read in the value
-                    std::vector<unsigned char> val_bytes;
-                    s >> val_bytes;
-                    unknown.emplace(std::move(key), std::move(val_bytes));
-                }
-            }
-        }
-
-        if (!found_sep) {
-            throw std::ios_base::failure("Separator is missing at the end of the global map");
-        }
-
-        // Make sure that we got an unsigned tx
-        if (!tx) {
-            throw std::ios_base::failure("No unsigned transcation was provided");
-        }
-
-        // Read input data
-        unsigned int i = 0;
-        while (!s.empty() && i < tx->vin.size()) {
-            PSBTInput input;
-            s >> input;
-            inputs.push_back(input);
-
-            // Make sure the non-witness utxo matches the outpoint
-            if (input.non_witness_utxo && input.non_witness_utxo->GetHash() != tx->vin[i].prevout.hash) {
-                throw std::ios_base::failure("Non-witness UTXO does not match outpoint hash");
-            }
-            ++i;
-        }
-        // Make sure that the number of inputs matches the number of inputs in the transaction
-        if (inputs.size() != tx->vin.size()) {
-            throw std::ios_base::failure("Inputs provided does not match the number of inputs in transaction.");
-        }
-
-        // Read output data
-        i = 0;
-        while (!s.empty() && i < tx->vout.size()) {
-            PSBTOutput output;
-            s >> output;
-            outputs.push_back(output);
-            ++i;
-        }
-        // Make sure that the number of outputs matches the number of outputs in the transaction
-        if (outputs.size() != tx->vout.size()) {
-            throw std::ios_base::failure("Outputs provided does not match the number of outputs in transaction.");
-        }
-        // Sanity check
-        if (!IsSane()) {
-            throw std::ios_base::failure("PSBT is not sane.");
-        }
-    }
-
-    template <typename Stream>
-    PartiallySignedTransaction(deserialize_type, Stream& s) {
-        Unserialize(s);
-    }
-};
-
 /** Produce a script signature using a generic signature creator. */
 bool ProduceSignature(const SigningProvider& provider, const BaseSignatureCreator& creator, const CScript& scriptPubKey, SignatureData& sigdata);
 
@@ -738,12 +204,6 @@ bool ProduceSignature(const SigningProvider& provider, const BaseSignatureCreato
 bool SignSignature(const SigningProvider &provider, const CScript& fromPubKey, CMutableTransaction& txTo, unsigned int nIn, const CAmount& amount, int nHashType);
 bool SignSignature(const SigningProvider &provider, const CTransaction& txFrom, CMutableTransaction& txTo, unsigned int nIn, int nHashType);
 
-/** Checks whether a PSBTInput is already signed. */
-bool PSBTInputSigned(PSBTInput& input);
-
-/** Signs a PSBTInput, verifying that all provided data matches what is being signed. */
-bool SignPSBTInput(const SigningProvider& provider, PartiallySignedTransaction& psbt, int index, int sighash = SIGHASH_ALL);
-
 /** Extract signature data from a transaction input, and insert it. */
 SignatureData DataFromTransaction(const CMutableTransaction& tx, unsigned int nIn, const CTxOut& txout);
 void UpdateInput(CTxIn& input, const SignatureData& data);
diff --git a/src/wallet/psbtwallet.cpp b/src/wallet/psbtwallet.cpp
new file mode 100644
index 0000000000..a62ad08370
--- /dev/null
+++ b/src/wallet/psbtwallet.cpp
@@ -0,0 +1,60 @@
+// Copyright (c) 2009-2018 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <rpc/protocol.h>
+#include <wallet/psbtwallet.h>
+
+bool FillPSBT(const CWallet* pwallet, PartiallySignedTransaction& psbtx, int sighash_type, bool sign, bool bip32derivs)
+{
+    LOCK(pwallet->cs_wallet);
+    // Get all of the previous transactions
+    bool complete = true;
+    for (unsigned int i = 0; i < psbtx.tx->vin.size(); ++i) {
+        const CTxIn& txin = psbtx.tx->vin[i];
+        PSBTInput& input = psbtx.inputs.at(i);
+
+        if (PSBTInputSigned(input)) {
+            continue;
+        }
+
+        // Verify input looks sane. This will check that we have at most one uxto, witness or non-witness.
+        if (!input.IsSane()) {
+            throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "PSBT input is not sane.");
+        }
+
+        // If we have no utxo, grab it from the wallet.
+        if (!input.non_witness_utxo && input.witness_utxo.IsNull()) {
+            const uint256& txhash = txin.prevout.hash;
+            const auto it = pwallet->mapWallet.find(txhash);
+            if (it != pwallet->mapWallet.end()) {
+                const CWalletTx& wtx = it->second;
+                // We only need the non_witness_utxo, which is a superset of the witness_utxo.
+                //   The signing code will switch to the smaller witness_utxo if this is ok.
+                input.non_witness_utxo = wtx.tx;
+            }
+        }
+
+        // Get the Sighash type
+        if (sign && input.sighash_type > 0 && input.sighash_type != sighash_type) {
+            throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "Specified Sighash and sighash in PSBT do not match.");
+        }
+
+        complete &= SignPSBTInput(HidingSigningProvider(pwallet, !sign, !bip32derivs), psbtx, i, sighash_type);
+    }
+
+    // Fill in the bip32 keypaths and redeemscripts for the outputs so that hardware wallets can identify change
+    for (unsigned int i = 0; i < psbtx.tx->vout.size(); ++i) {
+        const CTxOut& out = psbtx.tx->vout.at(i);
+        PSBTOutput& psbt_out = psbtx.outputs.at(i);
+
+        // Fill a SignatureData with output info
+        SignatureData sigdata;
+        psbt_out.FillSignatureData(sigdata);
+
+        MutableTransactionSignatureCreator creator(psbtx.tx.get_ptr(), 0, out.nValue, 1);
+        ProduceSignature(HidingSigningProvider(pwallet, true, !bip32derivs), creator, out.scriptPubKey, sigdata);
+        psbt_out.FromSignatureData(sigdata);
+    }
+    return complete;
+}
diff --git a/src/wallet/psbtwallet.h b/src/wallet/psbtwallet.h
new file mode 100644
index 0000000000..4f888a06ec
--- /dev/null
+++ b/src/wallet/psbtwallet.h
@@ -0,0 +1,14 @@
+// Copyright (c) 2009-2018 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_WALLET_PSBTWALLET_H
+#define BITCOIN_WALLET_PSBTWALLET_H
+
+#include <psbt.h>
+#include <primitives/transaction.h>
+#include <wallet/wallet.h>
+
+bool FillPSBT(const CWallet* pwallet, PartiallySignedTransaction& psbtx, int sighash_type = 1 /* SIGHASH_ALL */, bool sign = true, bool bip32derivs = false);
+
+#endif // BITCOIN_WALLET_PSBTWALLET_H
diff --git a/src/wallet/rpcwallet.cpp b/src/wallet/rpcwallet.cpp
index b01f40b125..905b183307 100644
--- a/src/wallet/rpcwallet.cpp
+++ b/src/wallet/rpcwallet.cpp
@@ -30,6 +30,7 @@
 #include <util/moneystr.h>
 #include <wallet/coincontrol.h>
 #include <wallet/feebumper.h>
+#include <wallet/psbtwallet.h>
 #include <wallet/rpcwallet.h>
 #include <wallet/wallet.h>
 #include <wallet/walletdb.h>
@@ -3948,60 +3949,6 @@ void AddKeypathToMap(const CWallet* pwallet, const CKeyID& keyID, std::map<CPubK
     hd_keypaths.emplace(vchPubKey, std::move(info));
 }
 
-bool FillPSBT(const CWallet* pwallet, PartiallySignedTransaction& psbtx, int sighash_type, bool sign, bool bip32derivs)
-{
-    LOCK(pwallet->cs_wallet);
-    // Get all of the previous transactions
-    bool complete = true;
-    for (unsigned int i = 0; i < psbtx.tx->vin.size(); ++i) {
-        const CTxIn& txin = psbtx.tx->vin[i];
-        PSBTInput& input = psbtx.inputs.at(i);
-
-        if (PSBTInputSigned(input)) {
-            continue;
-        }
-
-        // Verify input looks sane. This will check that we have at most one uxto, witness or non-witness.
-        if (!input.IsSane()) {
-            throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "PSBT input is not sane.");
-        }
-
-        // If we have no utxo, grab it from the wallet.
-        if (!input.non_witness_utxo && input.witness_utxo.IsNull()) {
-            const uint256& txhash = txin.prevout.hash;
-            const auto it = pwallet->mapWallet.find(txhash);
-            if (it != pwallet->mapWallet.end()) {
-                const CWalletTx& wtx = it->second;
-                // We only need the non_witness_utxo, which is a superset of the witness_utxo.
-                //   The signing code will switch to the smaller witness_utxo if this is ok.
-                input.non_witness_utxo = wtx.tx;
-            }
-        }
-
-        // Get the Sighash type
-        if (sign && input.sighash_type > 0 && input.sighash_type != sighash_type) {
-            throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "Specified Sighash and sighash in PSBT do not match.");
-        }
-
-        complete &= SignPSBTInput(HidingSigningProvider(pwallet, !sign, !bip32derivs), psbtx, i, sighash_type);
-    }
-
-    // Fill in the bip32 keypaths and redeemscripts for the outputs so that hardware wallets can identify change
-    for (unsigned int i = 0; i < psbtx.tx->vout.size(); ++i) {
-        const CTxOut& out = psbtx.tx->vout.at(i);
-        PSBTOutput& psbt_out = psbtx.outputs.at(i);
-
-        // Fill a SignatureData with output info
-        SignatureData sigdata;
-        psbt_out.FillSignatureData(sigdata);
-
-        MutableTransactionSignatureCreator creator(psbtx.tx.get_ptr(), 0, out.nValue, 1);
-        ProduceSignature(HidingSigningProvider(pwallet, true, !bip32derivs), creator, out.scriptPubKey, sigdata);
-        psbt_out.FromSignatureData(sigdata);
-    }
-    return complete;
-}
-
 UniValue walletprocesspsbt(const JSONRPCRequest& request)
 {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
diff --git a/src/wallet/rpcwallet.h b/src/wallet/rpcwallet.h
index abd7750874..58053bde59 100644
--- a/src/wallet/rpcwallet.h
+++ b/src/wallet/rpcwallet.h
@@ -30,5 +30,4 @@ bool EnsureWalletIsAvailable(CWallet *, bool avoidException);
 
 UniValue getaddressinfo(const JSONRPCRequest& request);
 UniValue signrawtransactionwithwallet(const JSONRPCRequest& request);
-bool FillPSBT(const CWallet* pwallet, PartiallySignedTransaction& psbtx, int sighash_type = 1 /* SIGHASH_ALL */, bool sign = true, bool bip32derivs = false);
 #endif //BITCOIN_WALLET_RPCWALLET_H
diff --git a/src/wallet/test/psbt_wallet_tests.cpp b/src/wallet/test/psbt_wallet_tests.cpp
index 9918eeb89f..0c5b7c7e98 100644
--- a/src/wallet/test/psbt_wallet_tests.cpp
+++ b/src/wallet/test/psbt_wallet_tests.cpp
@@ -5,6 +5,7 @@
 #include <key_io.h>
 #include <script/sign.h>
 #include <util/strencodings.h>
+#include <wallet/psbtwallet.h>
 #include <wallet/rpcwallet.h>
 #include <wallet/wallet.h>
 #include <univalue.h>