# BitcoinTx ## BitcoinTx Allows to reference Bitcoin raw transaction in Solidity. See Raw Bitcoin transaction data: | Bytes | Name | BTC type | Description | | ------ | -------------- | --------------------- | ------------------------- | | 4 | version | int32\_t (LE) | TX version number | | varies | tx\_in\_count | compactSize uint (LE) | Number of TX inputs | | varies | tx\_in | txIn\[] | TX inputs | | varies | tx\_out\_count | compactSize uint (LE) | Number of TX outputs | | varies | tx\_out | txOut\[] | TX outputs | | 4 | lock\_time | uint32\_t (LE) | Unix time or block number | Non-coinbase transaction input (txIn): | Bytes | Name | BTC type | Description | | ------ | ----------------- | --------------------- | ------------------------------------------- | | 36 | previous\_output | outpoint | The previous outpoint being spent | | varies | script\_bytes | compactSize uint (LE) | The number of bytes in the signature script | | varies | signature\_script | char\[] | The signature script, empty for P2WSH | | 4 | sequence | uint32\_t (LE) | Sequence number | The reference to transaction being spent (outpoint): | Bytes | Name | BTC type | Description | | ----- | ----- | -------------- | ---------------------------------------- | | 32 | hash | char\[32] | Hash of the transaction to spend | | 4 | index | uint32\_t (LE) | Index of the specific output from the TX | Transaction output (txOut): | Bytes | Name | BTC type | Description | | ------ | ----------------- | --------------------- | ------------------------------------ | | 8 | value | int64\_t (LE) | Number of satoshis to spend | | 1+ | pk\_script\_bytes | compactSize uint (LE) | Number of bytes in the pubkey script | | varies | pk\_script | char\[] | Pubkey script | compactSize uint format: | Value | Bytes | Format | | --------------------------------------- | ----- | --------------------------------------------- | | >= 0 && <= 252 | 1 | uint8\_t | | >= 253 && <= 0xffff | 3 | 0xfd followed by the number as uint16\_t (LE) | | >= 0x10000 && <= 0xffffffff | 5 | 0xfe followed by the number as uint32\_t (LE) | | >= 0x100000000 && <= 0xffffffffffffffff | 9 | 0xff followed by the number as uint64\_t (LE) | (\*) compactSize uint is often references as VarInt) Coinbase transaction input (txIn): | Bytes | Name | BTC type | Description | | ------ | ---------------- | --------------------- | ------------------------------------------- | | 32 | hash | char\[32] | A 32-byte 0x0 null (no previous\_outpoint) | | 4 | index | uint32\_t (LE) | 0xffffffff (no previous\_outpoint) | | varies | script\_bytes | compactSize uint (LE) | The number of bytes in the coinbase script | | varies | height | char\[] | The block height of this block (BIP34) (\*) | | varies | coinbase\_script | none | Arbitrary data, max 100 bytes | | 4 | sequence | uint32\_t (LE) | Sequence number | (\*) Uses script language: starts with a data-pushing opcode that indicates how many bytes to push to the stack followed by the block height as a little-endian unsigned integer. This script must be as short as possible, otherwise it may be rejected. The data-pushing opcode will be 0x03 and the total size four bytes until block 16,777,216 about 300 years from now. ### Info ```solidity struct Info { bytes4 version; bytes inputVector; bytes outputVector; bytes4 locktime; } ``` ### Proof ```solidity struct Proof { bytes merkleProof; uint256 txIndexInBlock; bytes bitcoinHeaders; } ``` ### UTXO ```solidity struct UTXO { bytes32 txHash; uint32 txOutputIndex; uint64 txOutputValue; } ``` ### RSVSignature ```solidity struct RSVSignature { bytes32 r; bytes32 s; uint8 v; } ``` ### validateProof ```solidity function validateProof(struct BridgeState.Storage self, struct BitcoinTx.Info txInfo, struct BitcoinTx.Proof proof) internal view returns (bytes32 txHash) ``` Validates the SPV proof of the Bitcoin transaction. Reverts in case the validation or proof verification fail. #### Parameters | Name | Type | Description | | ------ | -------------------------- | ------------------------- | | self | struct BridgeState.Storage | | | txInfo | struct BitcoinTx.Info | Bitcoin transaction data. | | proof | struct BitcoinTx.Proof | Bitcoin proof data. | #### Return Values | Name | Type | Description | | ------ | ------- | -------------------------------- | | txHash | bytes32 | Proven 32-byte transaction hash. | ### evaluateProofDifficulty ```solidity function evaluateProofDifficulty(struct BridgeState.Storage self, bytes bitcoinHeaders) internal view ``` Evaluates the given Bitcoin proof difficulty against the actual Bitcoin chain difficulty provided by the relay oracle. Reverts in case the evaluation fails. #### Parameters | Name | Type | Description | | -------------- | -------------------------- | ------------------------------------------------------------------------------------------------- | | self | struct BridgeState.Storage | | | bitcoinHeaders | bytes | Bitcoin headers chain being part of the SPV proof. Used to extract the observed proof difficulty. | ### extractPubKeyHash ```solidity function extractPubKeyHash(struct BridgeState.Storage, bytes output) internal pure returns (bytes20 pubKeyHash) ``` Extracts public key hash from the provided P2PKH or P2WPKH output. Reverts if the validation fails. Requirements: * The output must be of P2PKH or P2WPKH type and lock the funds on a 20-byte public key hash. #### Parameters | Name | Type | Description | | ------ | -------------------------- | ----------------------- | | | struct BridgeState.Storage | | | output | bytes | The transaction output. | #### Return Values | Name | Type | Description | | ---------- | ------- | -------------------------------------------------- | | pubKeyHash | bytes20 | 20-byte public key hash the output locks funds on. | ### makeP2PKHScript ```solidity function makeP2PKHScript(bytes20 pubKeyHash) internal pure returns (bytes26) ``` Build the P2PKH script from the given public key hash. The P2PKH script has the following byte format: <0x1976a914> <20-byte PKH> <0x88ac>. According to this translates to: * 0x19: Byte length of the entire script * 0x76: OP\_DUP * 0xa9: OP\_HASH160 * 0x14: Byte length of the public key hash * 0x88: OP\_EQUALVERIFY * 0xac: OP\_CHECKSIG which matches the P2PKH structure as per: #### Parameters | Name | Type | Description | | ---------- | ------- | ---------------------------- | | pubKeyHash | bytes20 | The 20-byte public key hash. | #### Return Values | Name | Type | Description | | ---- | ------- | ----------------- | | \[0] | bytes26 | The P2PKH script. | ### makeP2WPKHScript ```solidity function makeP2WPKHScript(bytes20 pubKeyHash) internal pure returns (bytes23) ``` Build the P2WPKH script from the given public key hash. The P2WPKH script has the following format: <0x160014> <20-byte PKH>. According to this translates to: * 0x16: Byte length of the entire script * 0x00: OP\_0 * 0x14: Byte length of the public key hash which matches the P2WPKH structure as per: #### Parameters | Name | Type | Description | | ---------- | ------- | ---------------------------- | | pubKeyHash | bytes20 | The 20-byte public key hash. | #### Return Values | Name | Type | Description | | ---- | ------- | ------------------ | | \[0] | bytes23 | The P2WPKH script. | --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.threshold.network/app-development/tbtc-contracts-api/tbtc-v2-api/bitcointx.md?ask= ``` The question should be specific, self-contained, and written in natural language. 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