PuTTYgen

PuTTYgen, short for PuTTY key generator, is a key-generation utility that is part of the PuTTY project. It is used to create public-private key pairs for SSH authentication and to convert keys between formats used by PuTTY and other SSH clients.

PuTTYgen runs as a graphical application on Windows and is included with the PuTTY distribution. Users can select the algorithm (RSA, DSA, ECDSA, Ed25519) and, for RSA, the key size (commonly up to 4096 bits). During generation, the program requests mouse movement to generate entropy. A passphrase can be added to protect the private key.

After generation, the private key can be saved in PuTTY's proprietary PPK format for use with PuTTY and Pageant, or exported as PEM for use with other SSH clients. The public key is shown in OpenSSH format so it can be copied to a server. PuTTYgen can also load existing private keys and convert between formats, or export the public key in different SSH formats.

PuTTYgen is typically used in conjunction with Pageant, the authentication agent, to enable passwordless SSH logins. It is a central tool for SSH key management within Windows environments and remains part of the standard PuTTY distribution.