John The Reaper error solved

Introduction

When using tools like ssh2john, which is part of the John the Ripper utility suite, you might run into an error like this:

File "/usr/bin/ssh2john", line 194, in <module>
  read_private_key(filename)
File "/usr/bin/ssh2john", line 154, in read_private_key
  saltstr = data[salt_offset:salt_offset+salt_length].encode("hex")
AttributeError: 'bytes' object has no attribute 'encode'. Did you mean: 'decode'?

This error happens because the script was originally written for Python 2, where you could do:

some_bytes.encode("hex")

However, in Python 3—the standard nowadays—that method is no longer valid. Instead, you should use:

some_bytes.hex()

Or if you’re working with encoded strings:

some_bytes.decode('utf-8')

But since the script hasn’t been updated, and you’re using an old version of John the Ripper installed via your package manager (pacman -S john or apt install john), it throws this Python error.

The Quick Fix

This problem is easily solved by installing the up-to-date GitHub version of John the Ripper. It’s Python 3 compatible and works smoothly.

On Arch Linux:

sudo pacman -S john-git

Or if you’re using yay:

yay -S john-git

On Debian/Ubuntu (if john-git is available):

sudo apt install john-git

If it’s not available, just clone and compile it manually:

git clone https://github.com/openwall/john.git
cd john/src
./configure && make -s clean && make -sj4