bitcoin-bips/bip-0174.mediawiki

<pre>
  BIP: 174
  Layer: Applications
  Title: Partially Signed Bitcoin Transaction Format
  Author: Andrew Chow <achow101@gmail.com>
  Comments-Summary: No comments yet.
  Comments-URI: https://github.com/bitcoin/bips/wiki/Comments:BIP-0174
  Status: Draft
  Type: Standards Track
  Created: 2017-07-12
  License: BSD-2-Clause
</pre>

==Introduction==

===Abstract===

This document proposes a binary transaction format which contains the information
necessary for a signer to produce signatures for the transaction and holds the
signatures for an input while the input does not have a complete set of signatures.
The signer can be offline as all necessary information will be provided in the
transaction.

===Copyright===

This BIP is licensed under the 2-clause BSD license.

===Motivation===

Creating unsigned or partially signed transactions to be passed around to multiple
signers is currently implementation dependent, making it hard for people who use
different wallet software from being able to easily do so. One of the goals of this
document is to create a standard and extensible format that can be used between clients to allow
people to pass around the same transaction to sign and combine their signatures. The
format is also designed to be easily extended for future use which is harder to do
with existing transaction formats.

Signing transactions also requires users to have access to the UTXOs being spent. This transaction
format will allow offline signers such as air-gapped wallets and hardware wallets
to be able to sign transactions without needing direct access to the UTXO set and without
risk of being defrauded.

==Specification==

The Partially Signed Bitcoin Transaction (PSBT) format consists of key-value maps.
Each key-value pair must have a unique key within its scope; duplicates are not allowed.
Each map consists of a sequence of records, terminated by a <tt>0x00</tt> byte <ref>'''Why
is the separator here <tt>0x00</tt> instead of <tt>0xff</tt>?'''
The separator here is used to distinguish between each chunk of data. A separator of 0x00 would mean that
the unserializer can read it as a key length of 0, which would never occur with actual keys. It can thus
be used as a separator and allow for easier unserializer implementation.</ref>. The format
of a record is as follows:

Note: <tt><..></tt> indicates that the data is prefixed by a compact size unsigned integer representing
the length of that data. <tt>{..}</tt> indicates the raw data itself.

<pre>
<key>|<value>
</pre>

{| class="wikitable" style="width: auto; text-align: center; font-size: smaller; table-layout: fixed;"
!Name
!Type
!Description
|-
| Key Length
| Compact Size Unsigned Integer
| Specify how long the key is
|-
| Key
| byte[]
| The key itself with the first byte being the type of the key-value pair
|-
| Value Length
| Compact Size Unsigned Integer
| Specify how long the value is
|-
| Value
| byte[]
| The Value itself
|}

The format of each key-value map is as follows:

<pre>
{key-value pair}|{key-value pair}|...|{0x00}
</pre>

{| class="wikitable" style="width: auto; text-align: center; font-size: smaller; table-layout: fixed;"
!Field Size
!Name
!Type
!Value
!Description
|-
| 1+
| Key-value pairs
| Array of key-value pairs
| varies
| The key-value pairs.
|-
| 1
| separator
| char
| <tt>0x00</tt>
| Must be <tt>0x00</tt>.
|}

The first byte of each key specifies the type of the key-value pair. There are global types,
per-input types, and per-output types.

The currently defined global types are as follows:

* Type: Unsigned Transaction <tt>PSBT_GLOBAL_UNSIGNED_TX = 0x00</tt>
** Key: None. The key must only contain the 1 byte type.
*** <tt>{0x00}</tt>
** Value: The transaction in network serialization. The scriptSigs and witnesses for each input must be empty. The transaction must be in the old serialization format (without witnesses). A PSBT must have a transaction, otherwise it is invalid.
*** <tt>{transaction}</tt>
** Note: Every PSBT must have a field with this type.

The currently defined per-input types are defined as follows:

* Type: Non-Witness UTXO <tt>PSBT_IN_NON_WITNESS_UTXO = 0x00</tt>
** Key: None. The key must only contain the 1 byte type.
***<tt>{0x00}</tt>
** Value: The transaction in network serialization format the current input spends from. This should only be present for inputs which spend non-segwit outputs. However, if it is unknown whether an input spends a segwit output, this type should be used.
*** <tt>{transaction}</tt>

* Type: Witness UTXO <tt>PSBT_IN_WITNESS_UTXO = 0x01</tt>
** Key: None. The key must only contain the 1 byte type.
*** <tt>{0x01}</tt>
** Value: The entire transaction output in network serialization which the current input spends from. This should only be present for inputs which spend segwit outputs, including P2SH embedded ones.
*** <tt>{serialized transaction output({output value}|<scriptPubKey>)}</tt>

* Type: Partial Signature <tt>PSBT_IN_PARTIAL_SIG = 0x02</tt>
** Key: The public key which corresponds to this signature.
*** <tt>{0x02}|{public key}</tt>
** Value: The signature as would be pushed to the stack from a scriptSig or witness.
*** <tt>{signature}</tt>

* Type: Sighash Type <tt>PSBT_IN_SIGHASH_TYPE = 0x03</tt>
** Key: None. The key must only contain the 1 byte type.
*** <tt>{0x03}</tt>
** Value: The 32-bit unsigned integer specifying the sighash type to be used for this input. Signatures for this input must use the sighash type, finalizers must fail to finalize inputs which have signatures that do not match the specified sighash type. Signers who cannot produce signatures with the sighash type must not provide a signature.
*** <tt>{sighash type}</tt>

* Type: Redeem Script <tt>PSBT_IN_REDEEM_SCRIPT = 0x04</tt>
** Key: None. The key must only contain the 1 byte type.
*** <tt>{0x04}</tt>
** Value: The redeemScript for this input if it has one.
*** <tt>{redeemScript}</tt>

* Type: Witness Script <tt>PSBT_IN_WITNESS_SCRIPT = 0x05</tt>
** Key: None. The key must only contain the 1 byte type.
*** <tt>{0x05}</tt>
** Value: The witnessScript for this input if it has one.
*** <tt>{witnessScript}</tt>

* Type:  BIP 32 Derivation Path <tt>PSBT_IN_BIP32_DERIVATION = 0x06</tt>
** Key: The public key
*** <tt>{0x06}|{public key}</tt>
** Value: The master key fingerprint as defined by BIP 32 concatenated with the derivation path of the public key. The derivation path is represented as 32 bit unsigned integer indexes concatenated with each other. Public keys are those that will be needed to sign this input.
*** <tt>{master key fingerprint}|{32-bit int}|...|{32-bit int}</tt>

* Type: Finalized scriptSig <tt>PSBT_IN_FINAL_SCRIPTSIG = 0x07</tt>
** Key: None. The key must only contain the 1 byte type.
*** <tt>{0x07}</tt>
** Value: The Finalized scriptSig contains a fully constructed scriptSig with signatures and any other scripts necessary for the input to pass validation.
*** <tt>{scriptSig}</tt>

* Type: Finalized scriptWitness <tt>PSBT_IN_FINAL_SCRIPTWITNESS = 0x08</tt>
** Key: None. The key must only contain the 1 byte type.
*** <tt>{0x08}</tt>
** Value: The Finalized scriptWitness contains a fully constructed scriptWitness with signatures and any other scripts necessary for the input to pass validation.
*** <tt>{scriptWitness}</tt>

The currently defined per-output <ref>'''Why do we need per-output data?''' Per-output data allows signers
to verify that the outputs are going to the intended recipient. The output data can also be use by signers to
determine which outputs are change outputs and verify that the change is returning to the correct place.</ref> types are defined as follows:

* Type: Redeem Script <tt>PSBT_OUT_REDEEM_SCRIPT = 0x00</tt>
** Key: None. The key must only contain the 1 byte type.
*** <tt>{0x00}</tt>
** Value: The redeemScript for this output if it has one.
*** <tt>{redeemScript}</tt>

* Type: Witness Script <tt>PSBT_OUT_WITNESS_SCRIPT = 0x01</tt>
** Key: None. The key must only contain the 1 byte type.
*** <tt>{0x01}</tt>
** Value: The witnessScript for this output if it has one.
*** <tt>{witnessScript}</tt>

* Type:  BIP 32 Derivation Path <tt>PSBT_OUT_BIP32_DERIVATION = 0x02</tt>
** Key: The public key
*** <tt>{0x02}|{public key}</tt>
** Value: The master key fingerprint concatenated with the derivation path of the public key. The derivation path is represented as 32 bit unsigned integer indexes concatenated with each other. This must omit the index of the master key. Public keys are those needed to spend this output.
*** <tt>{master key fingerprint}|{32-bit int}|...|{32-bit int}</tt>

The transaction format is specified as follows:


<pre>
    {0x70736274}|{0xff}|{global key-value map}|{input key-value map}|...|{input key-value map}|{output key-value map}|...|{output key-value map}|
</pre>

{| class="wikitable" style="width: auto; text-align: center; font-size: smaller; table-layout: fixed;"
!Field Size
!Name
!Type
!Value
!Description
|-
| 4
| Magic Bytes
| int32_t
| <tt>0x70736274</tt>
| Magic bytes which are ASCII for psbt. <ref>'''Why use 4 bytes for psbt?''' The
transaction format needed to start with a 5 byte header which uniquely identifies
it. The first bytes were chosen to be the ASCII for psbt because that stands for
Partially Signed Bitcoin Transaction. </ref> This integer should be serialized
in most significant byte order.
|-
| 1
| separator
| char
| <tt>0xff</tt>
| Must be <tt>0xff</tt> <ref>'''Why Use a separator after the magic bytes?''' The separator
is part of the 5 byte header for PSBT. This byte is a separator of <tt>0xff</tt> because
this will cause any non-PSBT unserializer to fail to properly unserialize the PSBT
as a normal transaction. Likewise, since the 5 byte header is fixed, no transaction
in the non-PSBT format will be able to be unserialized by a PSBT unserializer.</ref>
|-
| 1+
| Global data
| Key-value Map
| varies
| The key-value pairs for all global data.
|-
| 1+
| Inputs
| Array of key-value maps
| varies
| The key-value pairs for each input as described above. Every input in the unsigned transaction must have a corresponding input map.
|-
| 1+
| Outputs
| Array of key-value maps
| varies
| The key-value pairs for each output as described above. Every output in the unsigned transaction must have a corresponding output map.
|}

Each block of data between separators can be viewed as a scope, and all separators
are required<ref>'''Why are all separators required?''' The separators are required
so that the unserializer knows which input it is unserializing data for.</ref>.
Types can be skipped when they are unnecessary. For example, if an input is a witness
input, then it should not have a Non-Witness UTXO key-value pair.

If the signer encounters key-value pairs that it does not understand, it must
pass those key-value pairs through when re-serializing the transaction.

All keys must have the data that they specify. If any key or value does not match the
specified format for that type, the PSBT must be considered invalid. For example, any
key that has no data except for the type specifier must only have the type specifier in
the key.

===Handling Duplicated Keys===

Keys within each scope should never be duplicated; all keys in the format are unique. PSBTs containing duplicate keys are invalid. However implementors
will still need to handle events where keys are duplicated when combining transactions with duplicated fields. In this event, the software may choose
whichever value it wishes.

==Responsibilities==

Using the transaction format involves many different responsibilities. Multiple responsibilities can be handled by a single entity, but each responsibility is specialized in what it should be capable of doing.

===Creator===

The Creator creates a new PSBT. It must create an unsigned transaction and place it in the PSBT.
The Creator must create empty input fields.

===Updater===

The Updater must only accept a PSBT.
The Updater adds information to the PSBT that it has access to. If it has the UTXO for an input, it should add it to the PSBT.
The Updater should also add redeemScripts, witnessScripts, and BIP 32 derivation paths to the input and output data if it knows them.

A single entity is likely to be both a Creator and Updater.

===Signer===

The Signer must only accept a PSBT.
The Signer must only use the UTXOs provided in the PSBT to produce signatures for inputs.
Before signing a non-witness output, the Signer must verify that the TXID of the non-witness UTXO matches the TXID specified in the unsigned transaction.
The Signer should not need any additional data sources, as all necessary information is provided in the PSBT format.
The Signer must only add data to a PSBT.
Any signatures created by the Signer must be added as a "Partial Signature" key-value pair for the respective input it relates to.
If a Signer cannot sign a transaction, it must not add a Partial Signature.

The Signer can additionally compute the addresses and values being sent, and the transaction fee,  optionally showing this data to the user as a confirmation of intent and the consequences of signing the PSBT.

Signers do not need to sign for all possible input types. For example, a signer may choose to only sign only Segwit inputs.

A single entity is likely to be both a Signer and an Updater as it can update a PSBT with necessary information prior to signing it.

===Combiner===

The Combiner can accept 1 or many PSBTs.
The Combiner must merge them into one PSBT (if possible), or fail.
The resulting PSBT must contain all of the key-value pairs from each of the PSBTs.
The Combiner must remove any duplicate key-value pairs, in accordance with the specification. It can pick arbitrarily when conflicts occur.
A Combiner must not combine two different PSBTs. PSBTs can be uniquely identified by <tt>0x00</tt> global transaction typed key-value pair.
For every type that a Combiner understands, it may refuse to combine PSBTs if it detects that there will be inconsistencies or conflicts for that type in the combined PSBT.

The Combiner does not need to know how to interpret scripts in order to combine PSBTs. It can do so without understanding scripts or the network serialization format.

===Input Finalizer===

The Input Finalizer must only accept a PSBT.
For each input, the Input Finalizer determines if the input has enough data to pass validation. If it does, it must construct the scriptSig and scriptWitness and place them into the input key-value map.
All other data except the UTXO and unknown fields in the input key-value map should be cleared from the PSBT. The UTXO should be kept to allow Transaction Extractors to verify the final network serialized transaction.

===Transaction Extractor===

The Transaction Extractor must only accept a PSBT.
It checks whether all inputs have complete scriptSigs and scriptWitnesses by checking for the presence of <tt>0x05</tt> Finalized scriptSig and <tt>0x06</tt> Finalized scriptWitness typed records. If they do, the Transaction Extractor should construct complete scriptSigs and scriptWitnesses and encode them into network serialized transactions. Otherwise the Extractor must not modify the PSBT.
The Extractor should produce a fully valid, network serialized transaction if all inputs are complete.

The Transaction Extractor does not need to know how to interpret scripts in order to extract the network serialized transaction. However it may be able to in order to validate the network serialized transaction at the same time.

A single entity is likely to be both a Transaction Extractor and an Input Finalizer.

==Extensibility==

The Partially Signed Transaction format can be extended in the future by adding
new types for key-value pairs. Backwards compatibilty will still be maintained as those new
types will be ignored and passed-through by signers which do not know about them.

If one byte type fields were to ever run out, new extensions can still be added by defining multi-byte types where the first byte signals that the next byte indicates the type and so on.

==Compatibility==

This transaction format is designed so that it is unable to be properly unserialized
by normal transaction unserializers. Likewise, a normal transaction will not be
able to be unserialized by an unserializer for the PSBT format.

==Examples==

===Manual CoinJoin Workflow===

<img src="bip-0174/coinjoin-workflow.png" align="middle"></img>

===2-of-3 Multisig Workflow===

<img src="bip-0174/multisig-workflow.png" align="middle"></img>

==Test Vectors==

The following test vectors are done with keys derived from the following master private key. Keypaths and individual private keys will be specified when necessary

<pre>
tprv8ZgxMBicQKsPdHrvvmuEXXZ7f5EheFqshqVmtPjeLLMjqwrWbSeuGDcgJU1icTHtLjYiGewa5zcMScbGSRR8AqB8A5wvB3XRdNYBDMhXpBS
</pre>

The following are invalid PSBTs:

{| class="wikitable" style="width: auto; text-align: center; font-size: smaller; table-layout: fixed;"
!Test Case
!Explanation
|-
| <pre>0200000001268171371edff285e937adeea4b37b78000c0566cbb3ad64641713ca42171bf6000000006a473044022070b2245123e6bf474d60c5b50c043d4c691a5d2435f09a34a7662a9dc251790a022001329ca9dacf280bdf30740ec0390422422c81cb45839457aeb76fc12edd95b3012102657d118d3357b8e0f4c2cd46db7b39f6d9c38d9a70abcb9b2de5dc8dbfe4ce31feffffff02d3dff505000000001976a914d0c59903c5bac2868760e90fd521a4665aa7652088ac00e1f5050000000017a9143545e6e33b832c47050f24d3eeb93c9c03948bc787b32e1300</pre>
| Network transaction, not PSBT format
|-
| <pre>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</pre>
| PSBT missing null terminator
|-
| <pre>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</pre>
| PSBT with one P2PKH input and one P2SH-P2WPKH input with only the first input signed, finalized, and skipped. Input index is specified but total input count is not given.
|-
| <pre>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</pre>
| PSBT with one P2PKH input and one P2SH-P2WPKH input with only the first input signed, finalized, and skipped. Total input count is given but second input does not have its index.
|}

The following are valid PSBTs:

{| class="wikitable" style="width: auto; text-align: center; font-size: smaller; table-layout: fixed;"
!Test Case
!Explanation
|-
| <pre>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</pre>
| PSBT with one P2PKH input which has a non-final scriptSig.
|-
| <pre>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</pre>
| PSBT with one P2PKH input which has a non-final scriptSig and has a sighash type specified.
|-
| <pre>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</pre>
| PSBT with one P2PKH input and one P2SH-P2WPKH input both with non-final scriptSigs. P2SH-P2WPKH input's redeemScript is available.
|-
| <pre>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</pre>
| PSBT with one P2PKH input and one P2SH-P2WPKH input with only the first input signed and finalized.
|-
| <pre>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</pre>
| PSBT with one P2PKH input and one P2SH-P2WPKH input with only the first input signed, finalized, and skipped. Input indexes are used.
|-
| <pre>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</pre>
| PSBT with one P2SH-P2WSH input of a 2-of-2 multisig, redeemScript, witnessScript, and keypaths are available. Contains one signature.
|}

A creator with only the following:

* Redeem Scripts:
** <tt>522103c8727ce35f1c93eb0be21406ee9a923c89219fe9c9e8504c8314a6a22d1295c02103c74dc710c407d7db6e041ee212d985cd2826d93f806ed44912b9a1da691c977352ae</tt>
** <tt>0020a8f44467bf171d51499153e01c0bd6291109fc38bd21b3c3224c9dc6b57590df</tt>
* Witness Scripts:
** <tt>522102e80dec31d167865c1685e9d7a9291e66a4ea22c65cfee324289a1667ccda3b87210258cbbc3cb295a8bebac233aadc7773978804993798be5390ab444f6dd4c5327e52ae</tt>
* UTXOs
** TXID: <tt>0a4381c05136c0cb44886a5df7c26f1930bcc2c12e00ec60e027c4378d7d8c2e</tt>, Index: <tt>1</tt>
*** scriptPubKey: <tt>a914203736c3c06053896d7041ce8f5bae3df76cc49187</tt>
*** value: 0.50000000
** TXID: <tt>2c4df245d00b491bdf24965adbbccdaa7f62ccac933d3e9377f336c60c4ea096</tt>, Index: <tt>0</tt>
*** scriptPubKey: <tt>a914f3ba8a120d960ae07d1dbe6f0c37fb4c926d76d587</tt>
*** value: 2.00000000

given this unsigned transaction:
<pre>02000000022e8c7d8d37c427e060ec002ec1c2bc30196fc2f75d6a8844cbc03651c081430a0100000000ffffffff96a04e0cc636f377933e3d93accc627faacdbcdb5a9624df1b490bd045f24d2c0000000000ffffffff01e02be50e0000000017a914b53bb0dc1db8c8d803e3e39f784d42e4737ffa0d8700000000</pre>
must create this PSBT:
<pre>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</pre>

Given the above PSBT, a signer with the following keys:
* <tt>cQxozhqme9dcDbxT97uDu1P32Cnywc5nAMhPtQwyWhVgQnP43WGH</tt>
* <tt>cP3ArXq5BpHE94R4buJ5uma4pyKvaWXUd5Bpsy3hS2zA69X9KMnM</tt>
must create this PSBT:
<pre>70736274ff01007c02000000022e8c7d8d37c427e060ec002ec1c2bc30196fc2f75d6a8844cbc03651c081430a0100000000ffffffff96a04e0cc636f377933e3d93accc627faacdbcdb5a9624df1b490bd045f24d2c0000000000ffffffff01e02be50e0000000017a914b53bb0dc1db8c8d803e3e39f784d42e4737ffa0d87000000001501203736c3c06053896d7041ce8f5bae3df76cc49147522103c8727ce35f1c93eb0be21406ee9a923c89219fe9c9e8504c8314a6a22d1295c02103c74dc710c407d7db6e041ee212d985cd2826d93f806ed44912b9a1da691c977352ae1501f3ba8a120d960ae07d1dbe6f0c37fb4c926d76d5220020a8f44467bf171d51499153e01c0bd6291109fc38bd21b3c3224c9dc6b57590df2102a8f44467bf171d51499153e01c0bd6291109fc38bd21b3c3224c9dc6b57590df47522102e80dec31d167865c1685e9d7a9291e66a4ea22c65cfee324289a1667ccda3b87210258cbbc3cb295a8bebac233aadc7773978804993798be5390ab444f6dd4c5327e52ae000100fdff0002000000018b2dd2f735d0a9338af96402a8a91e4841cd3fed882362e7329fb04f1ff65325000000006a473044022077bedfea9910c9ba4e00dec941dace974f8b47349992c5d4312c1cf5796cce5502206164e6bfff7ac11590064ca571583709337c8a38973db2e70f4e9d93b3bcce1d0121032d64447459784e37cb2dda366c697adbbdc8aae2ad6db74ed2dade39d75882fafeffffff0382b42a04000000001976a914da533648fd339d5797790e6bb1667d9e86fdfb6888ac80f0fa020000000017a914203736c3c06053896d7041ce8f5bae3df76cc4918700b4c4040000000017a914b53bb0dc1db8c8d803e3e39f784d42e4737ffa0d879e2f1300220203c74dc710c407d7db6e041ee212d985cd2826d93f806ed44912b9a1da691c977347304402202a690a7a8d5763839df48285dea09f8ca69accd0227db9b735858eb87512a35b02204d294da3240bb1b069b728ddd5ce77dab61a9edf8db996268775a79a62817286010001012000c2eb0b0000000017a914f3ba8a120d960ae07d1dbe6f0c37fb4c926d76d587220202e80dec31d167865c1685e9d7a9291e66a4ea22c65cfee324289a1667ccda3b87483045022100f75f171e172383026972f8ed9986dba1db1f4fd12c9530b27d216b0b9fea60ac02206b288ffdeb2c6aa5e6c24aea4294e91c384249b04b29977dff7d5d53d8db71520100</pre>

Given the above blank PSBT, a signer with the following keys:
* <tt>cUL8UxFiJjnLkkZwmmXDxmaNRQfEMDP44eZnSaiYR3KUJNv82chM</tt>
* <tt>cNQm3eSF9rQnpoUB8xThUVDfaeRVEckPK11rGB6LjweFdhwcCS4A</tt>
must create this PSBT:
<pre>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</pre>

Given both of the above PSBTs, a combiner must create this PSBT:
<pre>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</pre>

Given the above PSBT, a finalizer must create this complete Bitcoin transaction:
<pre>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</pre>

==Rationale==

<references/>

==Reference implementation==

The reference implementation of the PSBT format is available at https://github.com/achow101/bitcoin/tree/psbt.

==Acknowledgements==

Special thanks to Pieter Wuille for suggesting that such a transaction format should be made
and for coming up with the name and abbreviation of PSBT.

Thanks to Pieter Wuille, Gregory Maxwell, Jonathan Underwood, and Daniel Cousens for additional comments
and suggestions for improving this proposal.

==Appendix A: Data types and their specifications==

Any data types, their associated scope and BIP number must be defined here

{| class="wikitable" style="width: auto; text-align: center; font-size: smaller; table-layout: fixed;"
!Scope
!Type values
!Name
!BIP Number
|-
| Global
| 0
| PSBT_GLOBAL_UNSIGNED_TX
| BIP 174
|-
| Input
| 0
| PSBT_IN_NON_WITNESS_UTXO
| BIP 174
|-
| Input
| 1
| PSBT_IN_WITNESS_UTXO
| BIP 174
|-
| Input
| 2
| PSBT_IN_PARTIAL_SIG
| BIP 174
|-
| Input
| 3
| PSBT_IN_SIGHASH_TYPE
| BIP 174
|-
| Input
| 4
| PSBT_IN_REDEEM_SCRIPT
| BIP 174
|-
| Input
| 5
| PSBT_IN_WITNESS_SCRIPT
| BIP 174
|-
| Input
| 6
| PSBT_IN_BIP32_DERIVATION
| BIP 174
|-
| Input
| 7
| PSBT_IN_FINAL_SCRIPTSIG
| BIP 174
|-
| Input
| 8
| PSBT_IN_FINAL_SCRIPTWITNESS
| BIP 174
|-
| Output
| 0
| PSBT_OUT_REDEEM_SCRIPT
| BIP 174
|-
| Output
| 1
| PSBT_OUT_WITNESS_SCRIPT
| BIP 174
|-
| Output
| 2
| PSBT_OUT_BIP32_DERIVATION
| BIP 174
|}