file-transfer beginner

putty-tools

A Linux package that ships PuTTYgen and other PuTTY utilities — most useful for converting OpenSSH .pem keys into the .ppk format required by WinSCP and PuTTY.

#ssh#keys#putty#winscp#key-conversion
visit website ↗ github repository ↗

What it is

putty-tools is a Linux package that provides the command-line versions of PuTTY utilities, the most relevant being puttygen. PuTTY-based clients on Windows — including WinSCP — use their own private key format (.ppk) instead of the OpenSSH .pem format issued by AWS and most Linux-native tooling. puttygen handles the conversion in both directions: .pem to .ppk for use with WinSCP, and .ppk back to OpenSSH format if needed. On Windows the same tool ships as a GUI application called PuTTYgen, but the Linux package lets you script the conversion without leaving the terminal or touching a Windows machine at all.

Why I use it

Whenever I provision an EC2 instance or hand off server access to someone using WinSCP, the first blocker is always the key format. Rather than firing up a Windows machine and clicking through the PuTTYgen GUI, I convert the key directly on the server or my local Linux machine with a single puttygen command. It takes ten seconds and removes a step that would otherwise require walking someone through a GUI they’ve never seen.

Installation

# Debian / Ubuntu
sudo apt install putty-tools

# RHEL / Rocky / AlmaLinux
sudo dnf install putty

# Arch
sudo pacman -S putty

Common usage

# Convert an AWS .pem key to .ppk (WinSCP / PuTTY compatible)
puttygen key.pem -o key.ppk

# Specify output type explicitly (ppk version 2 for older WinSCP/PuTTY versions)
puttygen key.pem -o key.ppk --ppk-param version:2

# Convert a .ppk key back to OpenSSH private key format
puttygen key.ppk -O private-openssh -o key.pem

# Extract the public key from a .ppk file (OpenSSH authorized_keys format)
puttygen key.ppk -O public-openssh -o key.pub

# Generate a new RSA key pair and save as .ppk directly
puttygen -t rsa -b 4096 -o new-key.ppk

Note: PuTTY version 3 .ppk files are the default output in newer releases of puttygen. If the person receiving the key is on an older version of WinSCP or PuTTY (pre-0.75), pass --ppk-param version:2 to produce a v2 file they can open.

Key flags