What additional authentication method does SFTP use to ensure that data is secure?

SFTP (Secure File Transfer Protocol) is built on the SSH (Secure Shell) protocol, and it primarily uses SSH keys as a method of authentication to ensure a secure transfer of data. SSH keys are a pair of cryptographic keys used to authenticate and establish a secure connection between two parties. When using SSH keys, the client has a private key, while the corresponding public key is stored on the server. This method enhances security because it eliminates the need to send passwords over the network, which could potentially be intercepted by malicious actors.

The use of SSH keys also allows for stronger security measures, such as passphrase protection for the private key and the ability to disable password authentication entirely, ensuring that only those with the appropriate keys can access the data. This mechanism is fundamental to the security model of SFTP and plays a crucial role in safeguarding sensitive information during transfer.

In contrast, encryption keys are a part of the broader encryption process but do not specifically address authentication. APIs typically facilitate communication between applications rather than provide authentication methods, and while two-factor authentication does enhance security, it is not inherently a part of the SFTP protocol itself. Therefore, SSH keys are the integral feature that provides the additional layer of authentication in SFTP.