fzputtygen

fzputtygen [ -t keytype ] [ -b bits ] [ -q ] [ -o output-file ] [ -O output-type ] [ -C comment ] [ -P ] [ -p passphrase ] [ -L ] [ -l ] [ -h ] [ -V ] [ -E fingerprint-type ] [ -i input-file ] [ -W old-passphrase ] [ -w new-passphrase ] [ -z random-seed-file ]

-t keytype
    Specifies the type of key to generate. Supported types include rsa, dsa, ecdsa, and ed25519.

-b bits
    Sets the number of bits in the key. For RSA, common values are 2048 or 4096.

-q
    Enables quiet mode, suppressing verbose output during key generation or other operations.

-o output-file
    Specifies the file path where the generated or converted key (private or public) will be saved.

-O output-type
    Determines the format for the output. Common types are private (PuTTY's .ppk or OpenSSH private key), public (OpenSSH public key format), or fingerprint.

-C comment
    Assigns a comment to the generated or imported key, which is often visible in the public key.

-P
    Instructs fzputtygen to prompt for changing the passphrase of an existing key. Requires -i.

-p passphrase
    Specifies the new passphrase to be used when generating a key or changing an existing key's passphrase.

-L
    Loads a private key specified by -i and prints its fingerprint.

-l
    Loads a public key specified by -i and prints its fingerprint.

-h
    Displays a help message with available command-line options.

-V
    Displays the version information of fzputtygen.

-E fingerprint-type
    Specifies the algorithm to use for calculating the key fingerprint (e.g., md5, sha256).

-i input-file
    Specifies the file path of an existing private or public key to be loaded, converted, or have its passphrase changed.

-W old-passphrase
    Provides the current passphrase for an encrypted input key when performing operations like conversion or passphrase change.

new-passphrase
    Provides the new passphrase when generating a key or changing an existing key's passphrase, bypassing the prompt.

-z random-seed-file
    Specifies a file containing random data to seed the key generation process, enhancing randomness.

fzputtygen is a utility primarily associated with the FileZilla client, typically found on Windows, but functionally analogous to puttygen available on Linux. Its core purpose is to generate SSH (Secure Shell) key pairs, comprising a public and a private key. These keys are fundamental for secure authentication, especially in scenarios involving SSH, SFTP, and SCP connections.

The utility supports various key algorithms, including RSA, DSA, ECDSA, and Ed25519, allowing users to choose the appropriate security level and compatibility. A crucial feature is its ability to convert keys between different formats, notably PuTTY's proprietary PPK format and the widely used OpenSSH format. This interoperability is vital for users who need to use keys generated by PuTTY in OpenSSH environments (like Linux servers) or vice-versa. Users can add a passphrase to their private keys for an additional layer of security, protecting them even if the private key file is compromised. The public key can then be easily extracted for placement on remote servers, enabling password-less, secure authentication.

fzputtygen is typically bundled with the FileZilla client for Windows, and while its core functionality mirrors puttygen, it is not a standard, standalone command found in most Linux distributions. On Linux, users generally rely on the puttygen utility (if PuTTY tools are installed) or more commonly, the built-in ssh-keygen for SSH key management.

When dealing with keys, always ensure a strong, unique passphrase for private keys. Securely store private keys and restrict access to them. Be mindful of the differences between PuTTY's proprietary PPK format and the widely used OpenSSH format; proper conversion is necessary for interoperability across different SSH clients and servers.

fzputtygen excels at generating and converting keys between PuTTY's PPK format and the standard OpenSSH format. This is crucial for users who might generate keys on a Windows machine (using PuTTYgen/fzputtygen) and need to deploy them on a Linux server (which uses OpenSSH). The command facilitates seamless key exchange, bridging the gap between different SSH client ecosystems.

When generating keys, it's highly recommended to use a strong passphrase to encrypt the private key. This provides an additional layer of security, protecting the private key even if the file itself is compromised. fzputtygen allows setting and changing passphrases for this purpose, enhancing the overall security posture of SSH connections.

fzputtygen is a variant of puttygen, which is part of the PuTTY suite of network utilities. PuTTY was initially developed for Windows by Simon Tatham in 1998 as a free and open-source SSH, Telnet, Rlogin, and raw TCP client. puttygen was developed alongside it to facilitate the creation and management of SSH keys specifically for use with PuTTY.

The fzputtygen executable itself is a specific repackaging or rebranding of puttygen included within the FileZilla client distribution, particularly on Windows, to provide integrated key generation capabilities for SFTP connections. Its development history is thus intertwined with both the PuTTY project's evolution and FileZilla's need for an embedded key management tool, ensuring compatibility with PuTTY's key format and widespread SSH standards.

puttygen(1), ssh-keygen(1), ssh(1), sftp(1), scp(1)