PuTTYgen for Mac

Quick overview

PuTTYgen is a free, open-source utility for creating SSH key pairs. It ships with the PuTTY suite but is also available as a standalone download if you only need to generate public/private keys for use with clients like WinSCP. The program produces keys used for secure connections and digital signing.

Supported algorithms and protocol notes

PuTTYgen can produce several modern public-key types. It works with both SSH-1 and SSH-2 protocols, though protocol support differs by algorithm:

• Ed25519 — a modern curve-based algorithm optimized for speed and security
• ECDSA — elliptic-curve signatures with various curve options
• DSA — the Digital Signature Algorithm (less common today)
• RSA — available for legacy SSH-1 and for SSH-2 connections

Creating a new key pair

When you open PuTTYgen you are presented with two primary choices: generate a new key pair or load an existing one. The typical process for creating a new key is:

1. Choose the key type you want and specify the desired key size/strength.
2. Click Generate and wait for the tool to produce the pair.
3. Provide a descriptive comment and a secure passphrase to protect the private key.
4. Save the private key file to disk.
5. Export or copy the public key so it can be added to your server’s authorized_keys (you can use the Save public key button or copy the key text directly).

If you prefer, you do not have to copy the public key to the server immediately — the private key can be reloaded into PuTTYgen later to access the public key again.

Working with existing keys

PuTTYgen also lets you import previously generated key files. After loading a key, you can:

• Update the comment to better identify the key
• Change or set a passphrase to improve security
• Re-export or create additional copies of the public key for other servers

This makes it easy to maintain and reuse keys without regenerating them from scratch.

Summary

PuTTYgen simplifies SSH key management by letting you generate, save, and modify key pairs with a few simple actions. While it integrates with the PuTTY client, it can be used on its own whenever you need to create or manage keys for secure connections.