Libauth Instruction Sets

This directory contains all of Libauth's supported instruction sets.

Functionality that is shared among multiple instruction sets is typically included in the common directory, and VM-specific functionality is included in each respective VM directory.

Copy, Don't Complicate

While most of Libauth attempts to be DRY (Don't Repeat Yourself), instruction sets need not follow this approach.

If an upgrade proposal requires adding a new code path within a common operation, resist the urge to add flags to the operation. Instead, copy the operation into the instruction set's directory and modify it there.

Libauth instruction sets should be as clearly defined and readable as possible, ideally within a single CODE-instruction-set.ts file. While short-lived instruction sets may be defined by slightly extending an existing, similar instruction set (e.g. a proposed network upgrade or a close relative from a recent network split), VMs intended for long-term support in Libauth should usually have a single-file definition for readability.

These single-file instruction set files should generally only import operations from sibling files and the common directory.

Virtual Machine Support

Libauth aims to provide support for the Virtual Machine (VM) used by every public bitcoin-like network and for public upgrade proposals with stable technical specifications.

Where multiple VMs include similar functionality, Libauth's exported utilities should prefer the configuration used by the latest version of the Bitcoin Cash (BCH) VM.

When a pending upgrade specification for BCH has wide consensus and a well-established activation date, Libauth utilities may be upgraded prior to the new specification's mainnet activation.

If a proposed upgrade seems likely to cause a network split, Libauth will attempt to support both sides and may wait to select the next default VM until after the split occurs (or the disagreement is resolved).

Virtual Machine Deprecation

Generally, Libauth only maintains support for active VM versions. For example, BCH_2019_05 was an upgrade that:

• enabled Schnorr signature support in OP_CHECKSIG and OP_CHECKDATASIG
• added a clean-stack exception for SegWit recovery

The BCH_2019_05 VM version was replaced without a network split by the BCH_2019_11 upgrade, meaning BCH_2019_05 is no longer in use by any public network. As such, relevant code paths, flags, and other VM-specific functionality for BCH_2019_05 have been removed to simplify Libauth's code. (Of course, historical implementations will always remain available in the Git history and previously-released versions of Libauth.)