What Are the Key Differences Between SFTP and FTPS?

Before discussing the differences between SFTP and FTPS or determining which protocol is more secure, let’s review each protocol's definition and operation.

What is SFTP?

Secure File Transfer Protocol (SFTP) is a preferred method for organizations looking to secure file transfers across a network. SFTP, also known as SSH(Secure Shell) File Transfer Protocol, operates in binary mode—making the data unreadable to humans—which adds an extra layer of security.

Unlike FTP, which transmits files in plain text, SFTP encrypts data by operating over SSH. This encryption requires authentication through a password or SSH key before any data is sent, protecting it from malicious actors. SFTP leverages robust encryption algorithms such as Blowfish, AES (Advanced Encryption Standard), and SHA-2 (Standard Hashing Algorithm), helping to ensure a high level of security for sensitive information.

A key feature of SFTP is its single-connection, single-port setup for uploading and downloading files. This setup not only limits the number of access points for unauthorized users, enhancing security, but it also simplifies firewall configuration.

Beyond file transfer, SFTP offers comprehensive file management capabilities. Users can easily organize and delete files, manage directories, compress files, adjust permissions, and more. Through a command-line interface, SFTP commands allow users to navigate and control their files efficiently.

What is FTPS?

Like SFTP, File Transfer Protocol Secure was developed to help address some of FTP’s security shortcomings. However, instead of establishing secure SSH connections, FTPS leverages Secure Sockets Layer/Transport Layer (SSL/TLS) encryption to protect files during transmission.

FTPS operates through two channels: a control channel for commands (usually on port 21) and a data channel for file transfers (typically on port 989 or 990). Both channels can be encrypted using robust algorithms like AES or 3DES (Triple Data Encryption Standard). However, FTPS opens a new port for each file transfer or directory listing, complicating firewall management.

It’s also worth mentioning that FTPS has two security modes: implicit and explicit. In implicit FTPS, data transmission can’t occur until an SSL connection is established. With explicit FTPS, the sender and receiver negotiate to determine whether the data will be encrypted or sent in plaintext form.

While SFTP and FTPS are both based on FTP, they differ in their encryption methods, port usage, firewall compatibility, authentication techniques, platform compatibility, performance, and speed.

Protocol and Encryption

SFTP, an SSH-based protocol, encrypts all data and file transfers within a secure SSH tunnel. It uses public-key cryptography for authentication, allowing users to verify their identity with passwords or SSH keys. This setup ensures end-to-end encryption, securing both commands and responses.

In contrast, FTPS uses SSL/TLS encryption and X.509 certificates to secure both command and data channels. While effective, the separate channels can complicate firewall management. Both SSH and SSL/TLS are secure, though SSH is generally regarded as slightly more robust.

Port Usage

FTPS uses multiple ports for its control and data channels. Implicit FTPS typically relies on port 990 for control and port 989 for data, while explicit FTPS uses port 21 for the initial connection and opens additional ports for each file transfer or directory listing, complicating firewall settings.

However, SFTP requires only one port—usually port 22—for authentication, control, and data transfer, simplifying configuration and enhancing security. Though SFTP defaults to port 22, it can operate on any specified port. This single-port setup gives SFTP an edge in security and ease of management over FTPS.

Firewall Considerations

Firewalls are crucial in securing data transfers, but SFTP is generally more firewall-friendly than FTPS.

SFTP uses a single connection and port for both commands and data, simplifying firewall configuration and reducing potential vulnerabilities, as fewer open ports mean fewer access points for unauthorized users. This setup also allows firewalls to monitor traffic efficiently, focusing on one port rather than scanning multiple fluctuating ports.

In contrast, FTPS uses a dual-channel architecture, requiring multiple ports that open and close as needed. This complexity can lead to connection issues and make firewall management more challenging, as firewalls must adapt to handle multiple dynamic ports.

Authentication Methods

Both SFTP and FTPS can provide secure authentication methods, but they do so in different ways.

FTPS authorization process relies on public key infrastructure, usernames, passwords, or signed X.509 certificates. These digital documents serve as proof of identity for servers and clients and contain the public key, information about the subject (user, computer, devices, or service), and details about the issuing certificate authority. The client can then verify the X.509 certificate before proceeding with the connection and data transfer.

Since SFTP encrypts all data, it doesn’t need signed certificates like FTPS. Instead, it uses out-of-band authentication, a username/password combination, a public SSH key, or both. This method allows for a more streamlined authentication process, as users can connect securely without needing certificates.

Platform Compatibility

Regarding platform compatibility, SFTP has native support on Unix/Linux systems and can be used with Windows and macOS systems with built-in SSH clients or third-party software. These days, SFTP has been widely adopted, to the point that most modern servers support it.

FTPS compatibility can be more limited due to its reliance on SSL/TLS and the need for certificate management. Web browsers like Chrome are also slowly phasing out FTP support, which could impact FTPS.

Performance and Speed

If your organization needs a high-performance, fast file transfer protocol, FTPS is the better option. FTPS's simplicity and straightforwardness can transfer files much faster than SFTP.

Since SFTP is robust and flexible, it has higher resource overhead than FTPS, resulting in slower file deliveries. SFTP must acknowledge every packet in transit and encrypt data, which takes time and can impact transfer speeds. Data traveling across an unstable network connection or a long distance may experience additional delays.

SFTP Advantages:

• Single connection: SFTP uses just one connection, making file transfers easier to secure by requiring only one monitored and protected channel.
• Firewall-friendly: With only one port in use, SFTP simplifies firewall configurations and strengthens security by reducing open access points.
• Robust file management: SFTP supports various file management functions, such as renaming files, deleting directories, and altering file permissions, providing flexibility beyond basic transfers.

SFTP Disadvantages:

• Complex SSH key management: Managing SSH keys can be challenging, especially for larger organizations with many users.
• Higher resource demand: Due to continuous packet verification, SFTP can be less efficient than FTPS, potentially slowing down transfer speeds.
• Binary logs: SFTP logs in binary format, which aren’t human-readable without conversion tools, complicating troubleshooting and auditing.

FTPS Advantages:

• Widespread support: FTPS is widely supported and compatible with many SSL/TLS infrastructures, including .NET framework server-to-server, making it easy to integrate into existing setups.
• Readable data format: Unlike SFTP’s binary data, FTPS transmits data in a more human-readable format, simplifying log tracking and auditing for faster troubleshooting.

FTPS Disadvantages:

• Multiple data channels: FTPS requires at least two channels for control and data, which can complicate firewall configurations and increase security risks with additional open ports.
• SSL/TLS certificate management: Managing SSL/TLS certificates can add complexity to maintenance and demand more resources.
• Compatibility limitations: Not all FTP servers support SSL/TLS; older servers may lack compatibility, potentially limiting FTPS usability in some environments

Here are some common use cases and scenarios where SFTP and FTPS are most effective, offering guidance on which protocol best suits various transfer requirements.

When to Choose SFTP

SFTP can be an excellent choice for your organization if you:

• Prioritize network security: SFTP’s single-port setup and SSH-based encryption provide a robust security framework, minimizing the number of open ports and simplifying firewall configurations. The reliance on SSH keys or password authentication further strengthens access control and makes it more resilient against unauthorized access.
• Have modern devices and systems: SFTP is versatile and easy to implement across mixed-operating system environments. It supports Unix/Linux natively and is compatible with Windows and macOS.
• Need detailed file management capabilities: SFTP provides extensive file management functions beyond simple file transfers, including renaming, moving, and deleting files and directories. This feature is helpful for organizations looking for a protocol that integrates file management with transfer capabilities.

When to Choose FTPS

On the other hand, FTPS might be a better option if you:

• Have older devices and systems: While SFTP is compatible with most modern systems, FTPS is a better option if your organization has legacy systems, such as CVL or .NET frameworks.
• Need a fast file transfer or are dealing with one-time data transfers: For scenarios requiring high-speed data transfer over stable networks, FTPS may provide faster performance. This difference is because it has lower resource demands than SFTP, which verifies each data packet and can slow down in high-volume scenarios.
• Require readable logs and compliance-friendly protocols: FTPS’s data transmission method allows for easier human readability of logs, which can be useful for organizations needing clear audit trails and compliance-friendly recordkeeping.

Both SFTP and FTPS have advantages and disadvantages—your choice ultimately depends on your organization’s specific needs, security priorities, and existing infrastructure.

SFTP is an excellent option for organizations prioritizing secure, cross-platform compatibility and extensive file management capabilities. Its SSH-based encryption and single-port operation make SFTP great for companies operating in modern, mixed-OS environments. However, the slightly slower transfer speeds and the need to manage SSH keys may require additional resources for maintenance and setup.

On the other hand, FTPS is an ideal choice for organizations with legacy systems or established SSL/TLS infrastructures looking for a straightforward, fast file transfer protocol. It offers robust security with flexible authentication options through X.509 certificates and SSL/TLS-based encryption. Additionally, FTPS’s human-readable logs and faster data transfer can benefit compliance-driven industries or one-time large file transfers over stable networks.