SSH Key Authentication

What is SSH key authentication?

Secure Shell (SSH) key authentication is a form of remote access control commonly used in file transfer tools and often leveraged by major corporations and cloud data centers. The SSH protocol provides secure remote login, and key authentication is based on the generation of SSH keys, which are encrypted access credentials. A common form of key authentication is public key authentication, which allows access between a local machine and a remote server.

How secure is SSH authentication?

SSH key based authentication is typically more secure than relying on traditional usernames and passwords. User-made passwords are often too weak or not changed regularly enough, but SSH authentication is designed to offer an improved, automated, and more secure login method using encryption. For example, unlike traditional letter and number passwords, a private SSH key will be at least 1024 bits long, with highly secure SSH keys stretching up to 4096 bits.

How does SSH public key authentication work?

SSH public key authentication works by establishing a key pair to give specific users access to protected data. SSH authentication is built to limit remote access logins to the computer with the private key. The computer generates the cryptographic key pair, which includes a public key and a private key. The public key exists on the SSH server, and anyone with a copy of this public key can use it to encrypt data, so only the person with the private key can decrypt and read the data. The private key remains with the user on their local machine and corresponds to the public key, allowing the server to authenticate and send the encrypted data to the local device.

How do I set up public key authentication in Serv-U?

Admins can configure Serv-U to enable users to leverage public SSH authentication. Here are some key functions for enabling SFTP and public key authentication within Serv-U.

Configure Serv-U for public SSH authentication:

• Within the Serv-U management console, select the user account to use a private key to authenticate.
• Click Manage Keys within the User Information tab.
• Generate a key within Serv-U with Create Key or Add Key to add one from a third-party generator.
• In the Limits & Settings tab, select the password type.
• Set SSH Authentication Type to Public Key Only.
• Alternatively, admins can require users to authenticate with both a password and key by setting the SSH Authentication Type to Password and Public Key.

Use an existing private key:

• Use a command line tool or third-party tool to generate the .key private key file.

• Place this private key in a secured directory on the server.
• Within Serv-U, use the Browse button to find and select this file.
• Enter the password required to access the .key file, then click Save.

Create a private key within Serv-U:

• Click the Create Private Key button within the Serv-U dashboard.
• Enter a name for the private key and a corresponding output path for the certificate.
• Select the key type. While the RSA format is available, DSA is the preferred format.
• Select the key length. The default is 1024 bits, which provides the best performance. However, 4096 bits provides the best security, and 2048 bits supports a mix of good performance and security.
• Enter a password to secure the private key file.

Related Features and Tools

Other SolarWinds FTP client software:

• Serv-U File Transfer Protocol Server
• Serv-U Gateway

Other features:

• Integration and Customization
• High Availability
• Reverse Proxy Server
• Automated File Transfer