compactSignatureToSignature

Name: viem-go
Author: viem-go

Converts a CompactSignature back to a regular Signature

compactSignatureToSignature

Converts a CompactSignature (EIP-2098) back to a regular Signature with separate R, S, V, and YParity components.

Import

import "github.com/ChefBingbong/viem-go/utils/signature"

Usage

import "github.com/ChefBingbong/viem-go/utils/signature"

compact := &signature.CompactSignature{
  R:           "0x68a020a209d3d56c46f38cc50a33f704f4a9a10a59377f8dd762ac66910e9b90",
  YParityAndS: "0x7e865ad05c4035ab5792787d4a0297a43617ae897930a6fe4d822b8faea52064",
}

sig, err := signature.CompactSignatureToSignature(compact)
if err != nil {
  log.Fatal(err)
}

fmt.Printf("R: %s
", sig.R)
// R: 0x68a020a209d3d56c46f38cc50a33f704f4a9a10a59377f8dd762ac66910e9b90

fmt.Printf("S: %s
", sig.S)
// S: 0x7e865ad05c4035ab5792787d4a0297a43617ae897930a6fe4d822b8faea52064

fmt.Printf("YParity: %d
", sig.YParity)
// YParity: 0

Returns

Type: (*signature.Signature, error)

A regular signature with R, S, V, and YParity components.

Parameters

compactSignature (required)

Type: *signature.CompactSignature

The compact signature struct containing R and YParityAndS components.

compact := &signature.CompactSignature{
  R:           "0x68a020a209d3d56c46f38cc50a33f704f4a9a10a59377f8dd762ac66910e9b90",
  YParityAndS: "0x7e865ad05c4035ab5792787d4a0297a43617ae897930a6fe4d822b8faea52064",
}

sig, _ := signature.CompactSignatureToSignature(compact)

Implementation

This function:

Extracts yParity from the top bit (bit 7) of the first byte of YParityAndS
Clears the top bit to get the actual S value
Constructs a regular Signature with R, S, YParity, and V (derived from yParity)

Notes

The yParity is decoded from the top bit of the first byte of YParityAndS
If bit 7 is set, yParity = 1
If bit 7 is clear, yParity = 0
The V value is set to 27 (yParity=0) or 28 (yParity=1) for compatibility