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SFTP Ciphers: The Complete Guide

Secure File Transfer Protocol (SFTP) is an extension of the Secure Shell protocol (SSH) designed to provide secure file transfer capabilities. SFTP encrypts both commands and data, providing effective protection against common network security issues such as data eavesdropping and data theft. The security of an SFTP connection largely depends on the underlying SSH protocol's encryption ciphers. These ciphers are algorithms used for encryption and decryption of data transferred over the connection.

The Role of Ciphers in SFTP

SFTP stands as a secure extension of SSH protocol, designed not only for transferring files but also for executing a wide range of secure network operations. At its core, SFTP encrypts data using a variety of ciphers, ensuring that information remains confidential and integral during transmission. These ciphers are cryptographic algorithms that transform readable data into an unreadable format, which can only be reversed with the correct key. The choice of cipher is critical, influencing both the security and performance of data transfers.

Commonly Used SFTP Ciphers

Various encryption algorithms are employed to secure files during transfer, with several algorithms supported. These include industry-standard algorithms like 3DES, Blowfish, and Advanced Encryption Standard (AES).

AES (Advanced Encryption Standard)

AES is a cornerstone in the realm of encryption, renowned for its security and efficiency. Available in key lengths of 128, 192, and 256 bits, with AES-256 being the most secure, it operates in different modes such as Cipher Block Chaining (CBC) and Galois/Counter Mode (GCM). AES's widespread adoption in governmental and security-sensitive industries underscores its reliability.


Emerging as a high-performance alternative, ChaCha20 is a stream cipher particularly suited for environments lacking AES hardware acceleration. Its design focuses on speed and security in software implementations, often paired with Poly1305 for authentication, forming a powerful duo for encrypting data.

Blowfish and Twofish

Blowfish's simplicity and speed once made it a popular choice, though its 64-bit block size is now considered less secure for some applications. Twofish, its successor, offers a 128-bit block size and was a finalist in the AES selection process. Despite being overshadowed by AES, Twofish remains a secure option for encryption.

3DES (Triple Data Encryption Standard)

As an older encryption standard, 3DES applies the DES algorithm three times to each data block, providing a layer of security that was robust for its time. However, its slow performance and diminished security compared to newer standards have led to its decline in favor.


Predominantly used for key exchange and digital signatures rather than direct file encryption, RSA is foundational to secure data transmission. Its security is based on the computational difficulty of factoring large prime numbers, making it a staple in cryptographic protocols.


By understanding and carefully selecting the appropriate ciphers, organizations and individuals can safeguard their data against the prying eyes of unauthorized parties. If you want to dive deeper, we also have an article covering the SFTP Encryption Algorithms