Bitcoin learning

Learning of Bitcoin.

Scripts

P2PKH

Lock script: OP_DUP OP_HASH160 OP_PUSHBYTES_20 <PK_Hash> OP_EQUALVERIFY OP_CHECKSIG

Unlock script: OP_PUSHBYTES_71 <Signature> OP_PUSHBYTES_33 <PK>

Check:

• OP_HASH160(PK) = PK_Hash
• OP_EQUALVERIFY verify signature

Ref: rust-bitcoin/bitcoin/src/blockdata/script/borrowed.rs#L190

P2SH

Lock script: OP_HASH160 OP_PUSHBYTES_20 <Script_Hash> OP_EQUAL

Unlock script: OP_PUSHBYTES_* DATA1 OP_PUSHBYTES_* DATA2 ... OP_PUSHBYTES_* DATAn

DATAn is the redeem script.

Check:

• OP_HASH160(DATAn) = Script_Hash
• execute redeem script

Ref: rust-bitcoin/bitcoin/src/blockdata/script/borrowed.rs#L181

P2WPKH

The signature (witness) part is separated from the input part of the transaction, thereby improving the efficiency and scalability of the transaction. The locking script only contains the public key hash, while the unlocking script (witness) contains the signature and the public key.

Lock script: OP_0 OP_PUSHBYTES_20 <PK_Hash>

Unlock script: None

Witness: 0x02 0x48 Signature 0x21 PK

Check: same as P2PKH

Ref: rust-bitcoin/bitcoin/src/blockdata/script/borrowed.rs#L285

P2WSH

Lock script: OP_0 OP_PUSHBYTES_32 <Script_Hash>

Unlock script: None

Witness: stackitems(VarInt) stackitem1_size stackitem1 stackitem2_size stackitem2 ... stackitemn_size stackitemn

The stackitemn is the redeem script. Data1..n push into stack.

Check: same as P2SH

Ref: rust-bitcoin/bitcoin/src/blockdata/script/borrowed.rs#L277

rust-bitcoin/bitcoin/src/blockdata/witness.rs#L468

P2TR

Lock script: OP_1 OP_PUSHBYTES_32 <Taproot_PK>

Unlock script: None

Key path spending

witness: signature

• CheckSchnorrSignature(signature, Taproot_PK, hash(Lock Script) => sighash) == 1

Script path spending

witness: stackitems(VarInt) stackitem1_size stackitem1 stackitem2_size stackitem2... stackitemn_size stackitemn

stackitemn is control(internal_key, merkle_path), stackitemn-1 is script.

1. ComputeTapleafHash(script) => tapleaf_hash
2. ComputeTaprootMerkleRoot(control.merkle_path, tapleaf_hash) => merkle_root
3. ComputeTapTweakHash(&merkle_root) => merkle_root_hash
4. ComputeTapTweak(merkle_root_hash, control.internal_key) => control.internal_key + merkle_root_hash * G == control.Taproot_PK
5. execute script

Ref: rust-bitcoin/bitcoin/src/blockdata/script/borrowed.rs#L293

OP_RETURN

ASM: OP_RETURN <data>

The OP_RETURN standard locking script just contains the OP_RETURN opcode followed by a data push of up to 80 bytes. This data push can contain any data you like, but it's commonly used for storing ASCII-encoded text strings.

This locking script cannot be unlocked, so don't use it to lock up any amount of bitcoins.

Ref: rust-bitcoin/bitcoin/src/blockdata/script/borrowed.rs#L304

SigHash

SIGHASH_ALL

SIGHASH_ALL, given a transaction Tx, the signature applies to all of Tx’s inputs and all its outputs (see green bounding boxes). SIGHASH_ALL is applied by

1. Creating a copy of the transaction
2. Empty script_sigs for each input and replace with the script_pubkey they reference. This is done because the "signature is part of the script_sig and … can’t sign itself"
3. Make sure that no other fields are set to empty before the transaction is serialized (Tx_ser)
4. The flag 0x01 is added to the end of the serialized transaction and passed through a hashing function
5. This message is then signed by the signing algorithm to generate the signature

SIGHASH_NONE

SIGHASH_NONE, the signature applies to all of Tx’s inputs (see green bounding box) but to none of the outputs. The application process is as stated below:

1. Create a copy of the transaction
2. Empty each script_sig for all inputs and replace with the script_pubkey they reference
3. Empty out all output fields
4. Serialize the transaction
5. Append 0x02 to Tx_ser, hash, and then sign

SIGHASH_SINGLE

SIGHASH_SINGLE, all the inputs of the given transaction Tx are signed and one output that has the same index of one of the inputs being signed. This is essentially "authorizing all other inputs to go with a specific output".

1. Create a copy of the transaction
2. Empty script_sigs for each input and replace with the script_pubkey they reference
3. Empty out all output fields bar the specific output
4. Serialize the transaction
5. Append 0x03 to Tx_ser, hash, and then sign

SIGHASH_ANYONECANPAY

With ANYONECANPAY set for ALL, changes can be made to all inputs except the select input (index 0) and the outputs (see image below).

ANYONECANPAY set for NONE means that changes can be made to all outputs, and inputs except the current input.

ANYONECANPAY set for SINGLE means that changes can be made to all outputs except the output with a matching index with the current input. All other inputs can be modified, added, and/or removed.

Ref: Signature Hash Flags

Ordinals Inscriptions

Ordinals are a numbering scheme for satoshis that allows tracking and transferring individual sats. These numbers are called ordinal numbers. Satoshis are numbered in the order in which they're mined, and transferred from transaction inputs to transaction outputs first-in-first-out. Both the numbering scheme and the transfer scheme rely on order, the numbering scheme on the order in which satoshis are mined, and the transfer scheme on the order of transaction inputs and outputs. Thus the name, ordinals.

Ref: Ordinals

Utils

sha256 online: https://www.lzltool.com/data-sha256

ripemd160 online: http://web.chacuo.net/charsetripemd160

filter transactions: how-can-i-find-samples-for-p2tr-transactions-on-mainnet

hex2ascii: https://www.bejson.com/convert/ox2str/

hex2image: https://www.lzltool.com/hextoimage

Ref

OP_HASH160

res = ripemd160(sha256(data))

Witness

example tx: 2c3ce072e32f49644a40a3d92d979e7fdd7d3f38f49db3f08e55e5e2f17e409a

witness:

  "inputs": [
    {
      "coinbase": false,
      "txid": "3a702e3f03591c158e3e4fee843b8db875510767a8fbee645d866da51b0f83fa",
      "output": 1,
      "sigscript": "",
      "sequence": 4294967293,
      "pkscript": "0020a65a74e2f3b3da24513ab14baf090d1a4ff860aafee1713d2d92a46f16a19c86",
      "value": 40606358,
      "address": "bc1q5ed8fchnk0dzg5f6k9967zgdrf8lsc92lmshz0fdj2jx794pnjrqnux44d",
      "witness": [
        "",
        "3045022100a8370520fe61c9eb55eab0207702e0d8a77afcdf2243202203fb1268df333ee802203862ca029d0afd54a55bab007d3b38201b2c032cb8f841a523fe30fc99dcf49d01",
        "3045022100aff60b14af50f68506057760328e7012f5f821de824e4c9ef43f636eb27233d7022009e4a222073fd9161e2c39aae3120b23ad851ffb78ca9d375007780efbf3187c01",
        "52210209f1f641a9871acea5698cd38401aabd77a6f6bf1804f57d04b379cba9235fff210243333533dd38308b7660b7c89694dc606af241d364c6dd4161bf9a877ccc207821029f55600c0f8f87c1bec37a0310e0ae8558e4217475afd7e3db12e6ad35284ca153ae"
      ]
    }
  ]

redeem script:

hex: 52210209f1f641a9871acea5698cd38401aabd77a6f6bf1804f57d04b379cba9235fff210243333533dd38308b7660b7c89694dc606af241d364c6dd4161bf9a877ccc207821029f55600c0f8f87c1bec37a0310e0ae8558e4217475afd7e3db12e6ad35284ca153ae

ASM: OP_PUSHNUM_2 OP_PUSHBYTES_33 0209f1f641a9871acea5698cd38401aabd77a6f6bf1804f57d04b379cba9235fff OP_PUSHBYTES_33 0243333533dd38308b7660b7c89694dc606af241d364c6dd4161bf9a877ccc2078 OP_PUSHBYTES_33 029f55600c0f8f87c1bec37a0310e0ae8558e4217475afd7e3db12e6ad35284ca1 OP_PUSHNUM_3 OP_CHECKMULTISIG

P2TR example

example tx: 905ecdf95a84804b192f4dc221cfed4d77959b81ed66013a7e41a6e61e7ed530

How to check p2tr script? See in main.rs.

SIGHASH example

example tx: 6adf27a500eb592d49a1732ab338e38815f6d4986636566755a68b1147c57d18

How to calculate sighash of transaction? See in main.rs.