ShellCrypt

A Python utility for encrypting shell commands for use in assembly programs with multiple cryptographic methods. Turn your reconnaissance commands into obfuscated bytecode that blends into the binary landscape.

Features

• Multiple Encryption Methods:

  • XOR (single-byte key)
  • Multi-byte XOR (rotating key)
  • ROT cipher (byte rotation)
  • ChaCha20 (stream cipher)
  • AES-128 ECB (AES-NI compatible)

• Flexible Input/Output:

  • Encrypt single commands
  • Batch encrypt from file
  • Decrypt encrypted commands
  • Generate NASM-formatted output

• Assembly Integration:

  • Outputs NASM db directives
  • Includes length definitions
  • Optional label naming

Installation

Requirements

• Python 3.6+
• pycryptodome (only required for AES encryption)

Setup

# Clone the repository
git clone <your-repo-url>
cd command-encryption-tool

# Install dependencies (optional, only needed for AES)
pip install pycryptodome

Usage

Basic Examples

Encrypt a single command with XOR:

python3 encrypt_commands.py -c "whoami" -m xor -k 0xAA

Output:

    db 0xc5, 0xc4, 0xc6, 0xc8, 0xc2, 0xc0, 0
    ; length: 6, cmd: "whoami"

Encrypt with custom label:

python3 encrypt_commands.py -c "hostname" -m xor -k 0xAA -l cmd_hostname

Output:

cmd_hostname:
    db 0xc2, 0xcf, 0xd3, 0xd4, 0xc8, 0xc2, 0xc8, 0xc0, 0
cmd_hostname_len equ 8  ; "hostname"

Encryption Methods

Multi-byte XOR:

python3 encrypt_commands.py -c "ls -la" -m multibyte -mk 0xAA,0xBB,0xCC,0xDD

ROT Cipher:

python3 encrypt_commands.py -c "ls -la" -m rot -r 13

ChaCha20:

python3 encrypt_commands.py -c "whoami" -m chacha20

AES-128:

python3 encrypt_commands.py -c "hostname" -m aes

Batch Processing

Create a file commands.txt:

whoami
hostname
uname -a
cmd_ps:ps aux

Encrypt all commands:

python3 encrypt_commands.py -f commands.txt -m xor -k 0xAA -o encrypted_commands.asm

Decryption

Decrypt encrypted bytes:

python3 encrypt_commands.py -d "0xc5,0xc4,0xc6,0xc8,0xc2,0xc0" -m xor -k 0xAA

Output:

Decrypted: whoami

Command-Line Options

Option	Description
-c, --command	Command string to encrypt
-f, --file	File containing commands (one per line)
-d, --decrypt	Decrypt encrypted bytes (format: 0xXX,0xYY,...)
-m, --method	Encryption method: xor, multibyte, rot, chacha20, aes
-k, --key	Encryption key (hex: 0xAA or decimal: 170)
-mk, --multibyte-key	Multi-byte key (comma-separated: 0xAA,0xBB,0xCC,0xDD)
-r, --rotation	ROT cipher rotation amount (default: 13)
-l, --label	NASM label name (e.g., cmd_whoami)
-o, --output	Output file (default: stdout)

File Format

When using -f to batch process commands, the file format is:

# Comments start with #
command1
command2

# Optional: specify labels
label_name:command3

Integration with Assembly

The tool outputs NASM-compatible syntax that can be directly included in assembly programs:

section .data
    cmd_whoami:
        db 0xc5, 0xc4, 0xc6, 0xc8, 0xc2, 0xc0, 0
    cmd_whoami_len equ 6

section .text
    ; Decrypt in place
    mov rsi, cmd_whoami
    mov rcx, cmd_whoami_len
    mov al, 0xAA
decrypt_loop:
    xor byte [rsi], al
    inc rsi
    loop decrypt_loop

Encryption Details

XOR

Simple single-byte XOR with a key byte. Fast and easy to implement in assembly.

Multi-byte XOR

Rotating key XOR. More secure than single-byte XOR as it prevents frequency analysis.

ROT Cipher

Adds a rotation value to each byte. Simple Caesar cipher variant.

ChaCha20

Simplified stream cipher implementation. The Python version matches the assembly placeholder with key rotation.

AES-128 ECB

Industry-standard encryption using AES-NI instructions. Requires 16-byte key and pads data to 16-byte blocks.

Security Considerations

⚠️ Educational Purpose: This tool is designed for security research and educational purposes.

• XOR and ROT ciphers provide obfuscation, not strong encryption
• ECB mode (used in AES implementation) has known weaknesses for production use
• Default keys are included for demonstration only
• Always use unique, random keys in production scenarios

Contributing

Contributions are welcome! Please feel free to submit pull requests or open issues for bugs and feature requests.