Written by Alex Taylor | 11/18/2023


Secure File Transfer Protocol (SFTP), also known as SSH File Transfer Protocol, is a network protocol that provides file access, transfer, and management capabilities over any reliable data stream. It is typically used to provide secure file transfer capabilities between hosts on a network and is built as an extension of the Secure Shell protocol (SSH).

The primary purpose of SFTP is to ensure the secure transfer of data between a local and a remote host. Unlike its older counterpart, FTP, which transfers data in plain text, SFTP uses the SSH protocol to encrypt the data being transferred, providing security against unauthorized access during the transmission. This encryption ensures that even if the data transmission is intercepted, the content of the data cannot be understood without the proper encryption key.

Key Features of SFTP:

  • Encryption: SFTP encrypts data before it is sent over a network, providing security against eavesdropping and man-in-the-middle attacks.

  • Authentication: It supports multiple forms of authentication, including password authentication and public key authentication, ensuring that only authorized users can transfer files.

  • Data Integrity: SFTP checks the integrity of the data being transferred with cryptographic hashes to ensure that the data has not been tampered with.

  • File Management: Beyond file transfer, SFTP allows users to perform a range of file management tasks remotely, such as creating and deleting directories and files.

  • Resuming Transfers: It can resume interrupted transfers, allowing for the continuation of file transfer without starting from the beginning.

How SFTP Works:

  1. A user connects to a server by providing a username and authenticating using a password, an SSH key, or both.
  2. Once authenticated, the user can execute a set of commands similar to those available in a shell on the remote server to transfer and manage files.
  3. Data transfer begins, with the data being encrypted by the client's SSH subsystem and then sent to the server's SSH subsystem for decryption.

SFTP is often confused with FTP over SSL/TLS (FTPS), but they are distinct protocols. SFTP is an extension of SSH and is integrated into most modern SSH implementations. FTPS, on the other hand, is FTP with SSL for security. It uses separate control and data channels, while SFTP only uses one channel.

SFTP is widely used in business processes and workflows that require secure file transfer capabilities. It's a part of many automated processes and systems where files are moved between different systems and networks such as in financial services, healthcare, and other industries where data security is paramount.

In practical use, SFTP is accessed via command-line tools or through various third-party GUI applications that make it easier to transfer files without needing to use command-line syntax. Many programming languages also provide libraries to interact with SFTP servers to automate file transfers and other file operations securely.

In conclusion, SFTP provides a secure way to transfer files over a network. By leveraging the security mechanisms of SSH, it ensures that sensitive information remains confidential and unaltered during transit. With its additional file management capabilities, SFTP remains a critical tool for many organizations that prioritize data security.