Crate bitcoin_scripts

Bitcoin script types

Bitcoin doesn’t make a distinction between Bitcoin script coming from different sources, like scriptPubKey in transaction output or witness and scriptSig in transaction input. There are many other possible script containers for Bitcoin script: redeem script, witness script, taproot leaf scripts of different versions. In fact, any “script” of bitcoin::Script type can be used for inputs and outputs. What is a valid script for in one context will not be a valid script for some other. That would mean that in principle with existing bitcoin::Script type every input script can be used as an output script, leading to potentially harmful code coming from an unaware developer.

While all bitcoin::Scripts have the same parsing rules converting byte string into a set of instructions (i.e. the same syntax), there are multiple ways how the consensus meaning of these instructions will be interpreted under different contexts (different semantics). Moreover, the scripts may be nested - or to be committed into some other Bitcoin script – in a nested structures like in several layers, like redeemScript inside of scriptSig used for P2SH, or tapScript within witnessScript coming from witness field for Taproot. These nested layers do distinguish on the information they contain, since some of them only commit to the hashes of the nested scripts (bitcoin::ScriptHash, WitnessProgram) or public keys (bitcoin::PubkeyHash, bitcoin::WPubkeyHash), while other contain the full source of the script.

The present type system represents a solution to the problem: it distinguish different logical types by introducing Script wrapper types. It defines LockScript as bottom layer of a script, containing no other script commitments (in form of their hashes). It also defines types above on it: PubkeyScript (for whatever is there in scriptPubkey field of a bitcoin::TxOut), SigScript (for whatever comes from scriptSig field of bitcoin::TxIn), RedeemScript and WitnessScript. For taproot, we define LeafScript as a top level of specific script branch (see bitcoin::util::psbt::TapTree) and crate::TapScript as a type specific for the current 0xC0 tapleaf version semantics, defined in BIP-342.

There are conversion functions, which, for instance, can analyse PubkeyScript and if it is a custom script or P2PK return a LockScript type - or otherwise fail with error. These conversions functions reside in convert module. So with this type system one is always sure which semantic information it does contain.

Type conversion

LockScript -+-> (PubkeyScript + RedeemScript) -+-> SigScript
            |                                  +-> WitnessScript
            +-> PubkeyScript
            |
TapScript ----> LeafScript

PubkeyScript --?--> LockScript

Re-exports

pub use convert::ConvertInfo;

Modules

address

Address-related types for detailed payload analysis and memory-efficient processing.

convert

Helper traits and supplementary types for converting different types of scripts and keys into each other.

hlc

Hash-locked contract supporting data structures.

taproot

Taproot script tree implementation allowing arbitrary tree processing/ modification (see TaprootScriptTree structure).

Structs

LeafScript

Any valid branch of taproot script spending

LockScript

Script whose knowledge and satisfaction is required for spending some specific transaction output. This is the deepest nested version of Bitcoin script containing no hashes of other scripts, including P2SH redeemScript hashes or witnessProgram (hash or witness script), or public key hashes. It is also used for representing specific spending branch of the taproot script tree.

PubkeyScript

A content of scriptPubkey from a transaction output

RedeemScript

Redeem script as part of the witness or scriptSig structure; it is hashed for P2(W)SH output.

ScriptCode

A representation of scriptPubkey data used during SegWit signing procedure

ScriptSet

Scripting data for both transaction output and spending transaction input parts that can be generated from some complete bitcoin Script (LockScript) or public key using particular crate::ConvertInfo

SigScript

A content of scriptSig from a transaction input

TapScript

Script at specific taproot script spend path for 0xC0 tapleaf version, which semantics are defined in BIP-342.

WitnessProgram

Witness program: a part of post-segwit scriptPubkey; a data pushed to the stack following witness version

WitnessScript

A content of the script from witness structure; en equivalent of redeemScript for witness-based transaction inputs. However, unlike RedeemScript, WitnessScript produce SHA256-based hashes of WScriptHash type.

Traits

IntoNodeHash

Marker trait for all forms of hashes which may participate in the construction of taproot script tree.

Type Definitions

TapNodeHash

The hash value of a taptree node which may be a leaf node, branch node or a hidden node.