PSBT Handling

Signing with JS

See psbt_sign.js and follow instructions in that file.

Sample Unsigned

From BIP174 docs. Uses bitcoin-cli decodepsbt to parse. txid is fed6cd1fde4db4e13e7e800317e37f9cbd75ec364389670eeff80da993c7e560

bitcoin-cli -rpcuser=__cookie__ -rpcpassword=9e0ca21c70d6b7307b750c8012d12df04ef77d0c5754abc29a3ae31304d946ce decodepsbt cHNidP8BAKACAAAAAqsJSaCMWvfEm4IS9Bfi8Vqz9cM9zxU4IagTn4d6W3vkAAAAAAD+////qwlJoIxa98SbghL0F+LxWrP1wz3PFTghqBOfh3pbe+QBAAAAAP7///8CYDvqCwAAAAAZdqkUdopAu9dAy+gdmI5x3ipNXHE5ax2IrI4kAAAAAAAAGXapFG9GILVT+glechue4O/p+gOcykWXiKwAAAAAAAEHakcwRAIgR1lmF5fAGwNrJZKJSGhiGDR9iYZLcZ4ff89X0eURZYcCIFMJ6r9Wqk2Ikf/REf3xM286KdqGbX+EhtdVRs7tr5MZASEDXNxh/HupccC1AaZGoqg7ECy0OIEhfKaC3Ibi1z+ogpIAAQEgAOH1BQAAAAAXqRQ1RebjO4MsRwUPJNPuuTycA5SLx4cBBBYAFIXRNTfy4mVAWjTbr6nj3aAfuCMIAAAA

TXID from PSBT

=btc -build-file %/lib/btc/hoon
=psbt 'cHNidP8BAKACAAAAAqsJSaCMWvfEm4IS9Bfi8Vqz9cM9zxU4IagTn4d6W3vkAAAAAAD+////qwlJoIxa98SbghL0F+LxWrP1wz3PFTghqBOfh3pbe+QBAAAAAP7///8CYDvqCwAAAAAZdqkUdopAu9dAy+gdmI5x3ipNXHE5ax2IrI4kAAAAAAAAGXapFG9GILVT+glechue4O/p+gOcykWXiKwAAAAAAAEHakcwRAIgR1lmF5fAGwNrJZKJSGhiGDR9iYZLcZ4ff89X0eURZYcCIFMJ6r9Wqk2Ikf/REf3xM286KdqGbX+EhtdVRs7tr5MZASEDXNxh/HupccC1AaZGoqg7ECy0OIEhfKaC3Ibi1z+ogpIAAQEgAOH1BQAAAAAXqRQ1RebjO4MsRwUPJNPuuTycA5SLx4cBBBYAFIXRNTfy4mVAWjTbr6nj3aAfuCMIAAAA'

(get-txid:^psbt:btc psbt)
::  gives [wid=%32 dat=0xfed6.cd1f.de4d.b4e1.3e7e.8003.17e3.7f9c.bd75.ec36.4389.670e.eff8.0da9.93c7.e560]

Parse PSBT into Maps

=btc -build-file %/lib/btc/hoon
=psbt 'cHNidP8BAKACAAAAAqsJSaCMWvfEm4IS9Bfi8Vqz9cM9zxU4IagTn4d6W3vkAAAAAAD+////qwlJoIxa98SbghL0F+LxWrP1wz3PFTghqBOfh3pbe+QBAAAAAP7///8CYDvqCwAAAAAZdqkUdopAu9dAy+gdmI5x3ipNXHE5ax2IrI4kAAAAAAAAGXapFG9GILVT+glechue4O/p+gOcykWXiKwAAAAAAAEHakcwRAIgR1lmF5fAGwNrJZKJSGhiGDR9iYZLcZ4ff89X0eURZYcCIFMJ6r9Wqk2Ikf/REf3xM286KdqGbX+EhtdVRs7tr5MZASEDXNxh/HupccC1AaZGoqg7ECy0OIEhfKaC3Ibi1z+ogpIAAQEgAOH1BQAAAAAXqRQ1RebjO4MsRwUPJNPuuTycA5SLx4cBBBYAFIXRNTfy4mVAWjTbr6nj3aAfuCMIAAAA'

(parse:pbt:btc psbt)

Make an HD Path

=btc -build-file %/lib/btc/hoon
=hk [[%4 0x9ca7.9d5b] %bip84 %1 11]
=pubkey [33 0x3.6093.e9e0.6a5f.736e.751f.5486.c1c6.7647.c258.b946.b314.d2d3.f03a.33c2.b5cf.b9ab]
(hd-path:^psbt:btc pubkey %output hk)

:: GIVES
[ key=[wid=34 dat=0x203.6093.e9e0.6a5f.736e.751f.5486.c1c6.7647.c258.b946.b314.d2d3.f03a.33c2.b5cf.b9ab]
  val=[wid=21 dat=0x9c.a79d.5b54.0000.8000.0000.8000.0000.8001.0000.000b]]

Making Derivation Paths

Below is hex for m/84'/0'/0'/0/0 *80 is the ending for hardened paths* 54.00.00.80 00.00.00.80 00.00.00.80 00.00.00.00 00.00.00.00.00

CLI Debugging

bitcoin-cli -rpcuser=__cookie__ -rpcpassword=$(./rpc-password.sh) decodepsbt $PSBT

ColdCard PSBT Export Structure

If we don't have the master fingerprint, can probably fake it. It's not "load-bearing".

Maps:

1 keyval

Raw tx hex

3 keyvals (Input)

Witness TX: {8byte amount}|{1 byte scriptpubkeylen}|{22byte scriptpubkey)}
Non Witness TX: 82 byte input tx
Wallet Derivation path.
- Key: {0x6}|{33byte pubkey}
- Val: {4byte master xpub fingerprint}|{17byte HD path}

skips the main output for some reason, even though it's in raw tx hex. skips = double separator, I think we can skip an ouput if the path is on someone else's ship
1 keyval

Change output Wallet derivation path
- Key: {0x2}|{33byte pubkey}
- Val: {4byte master xpub fingerprint}|{17byte HD path}

Signed

Input: keeps above keyvals, and adds one more for the partial signature:

(key type {0x2}|{publicKey})
val: 71 byte signature

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