Overview • Quick Start • Interactive TUI • Targeted Bad-Byte Elimination • Bad-Byte Profiles • Features • Architecture • System Requirements • Dependencies • Building • Installation • Usage • Obfuscation Strategies • Denullification Strategies • ML Training • Agent Menagerie • Development • Troubleshooting • License

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Table of Contents

• Overview
• Quick-Start
  • Installation
  • Basic Usage
  • Verification
  • Cross-Architecture Support
  • Batch Processing
• Interactive TUI
• Targeted Bad-Byte Banishment
• Bad-Byte Profiles
• Features
  • Advanced Transformation Engine
  • Performance Metrics
  • Obfuscation Layer
  • ML-Powered Strategy Selection
  • Output Options
  • Verification Suite
• Architecture
• System Requirements
• Dependencies
• Building
• Installation
• Usage
• Obfuscation Strategies
• Denullification Strategies
• ML Training & Validation
• Agent Menagerie
• Development
• Documentation
• Troubleshooting
• License

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Overview

byvalver is a CLI tool built in C for automatically eliminating (or "banishing") bad-bytes from x86/x64/ARM/ARM64 shellcode while maintaining complete functional equivalence

NEW in v4.0: Cross-Architecture Support

Architecture	Maturity	Strategies	Notes
x86 (32-bit Intel/AMD)	Stable v4.2	150+	Production-tested, full coverage
x64 (64-bit Intel/AMD)	Stable v4.2	150+	Default architecture, production-tested
ARM (32-bit)	Experimental v0.1	7 core	Limited testing, core instructions only
ARM64 (AArch64)	Experimental v0.1	Basic	Framework ready, minimal strategies

• Automatic Capstone mode selection via --arch flag

v4.0.1 Bug Fixes:

• Fixed ARM SUB instruction encoding (correct opcode 0x2 with I=1 bit)
• Fixed ARM64 strategy can_handle logic for pass-through strategies
• Added experimental warnings when ARM/ARM64 architecture is selected
• Added architecture mismatch detection heuristics
• Improved code organization (includes moved to file scope)

NEW in v4.2: Enhanced x64 Support

• x86/x64 Strategy Compatibility Layer: 128+ x86 strategies now work on x64 shellcode
• 5 New x64-Specific Strategy Files: MOVABS, SBB, TEST, SSE Memory, LEA Displacement
• Extended Register Encoding: Full R8-R15 support with proper REX prefix handling
• REX Prefix Utilities: is_64bit_register(), is_extended_register(), build_rex_prefix()
• Resolves 100% failure rate on x64-only shellcode samples

The tool uses the Capstone disassembly framework to analyze instructions and applies over 175+ ranked transformation strategies to replace bad-byte-containing code with equivalent alternatives

The generic bad-byte banishment framework provides 2x usage modes:

1. Direct specification: The --bad-bytes option allows specification of arbitrary bytes to banish (e.g., --bad-bytes "00,0a,0d" for newline-safe shellcode)
2. Profile-based: The --profile option uses pre-configured bad-byte sets for common exploit scenarios (e.g., --profile http-newline, --profile sql-injection, --profile alphanumeric-only)

Supports Windows, Linux, and macOS

CORE TECH:

• Pure C implementation for efficiency and low-level control
• Capstone for precise disassembly
• NASM for generating decoder stubs
• Modular strategy pattern for extensible transformations (153+ strategy implementations)
• Neural network integration for intelligent strategy selection
• Biphasic processing: Obfuscation followed by denullification

[!NOTE] Null-byte elimination (--bad-bytes "00" or default): WELL-TESTED / Generic bad-byte elimination (--bad-bytes "00,0a,0d" etc.): NEWLY IMPLEMENTED

BAD-BYTE BANISHMENT IN ACTION

QUICK-START

Get started with byvalver in minutes:

INSTALLATION

OPTION 1: FROM GITHUB (RECOMMENDED)

curl -sSL https://raw.githubusercontent.com/umpolungfish/byvalver/main/install.sh | bash

OPTION 2: BUILD FROM SOURCE

git clone https://github.com/umpolungfish/byvalver.git
cd byvalver
make
sudo make install
sudo make install-man  # Install man page

Basic Usage

banish NULL BYTES (DEFAULT):

byvalver input.bin output.bin

USING BAD-BYTE PROFILES:

# HTTP contexts (removes null, newline, carriage return)
byvalver --profile http-newline input.bin output.bin

# SQL injection contexts
byvalver --profile sql-injection input.bin output.bin

# Alphanumeric-only shellcode (most restrictive)
byvalver --profile alphanumeric-only input.bin output.bin

MANUAL BAD-BYTE SPECIFICATION:

# banish null bytes and newlines
byvalver --bad-bytes "00,0a,0d" input.bin output.bin

ADVANCED FEATURES:

# Add obfuscation layer before denullification
byvalver --biphasic input.bin output.bin

# Enable ML-powered strategy selection
byvalver --ml input.bin output.bin