Rebex Buru SFTP Server 2.18.0: Post-quantum cryptography and SSH/SFTP core improvements

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We have released Rebex Buru SFTP Server v2.18.0. Here is an overview of changes, fixes and improvements.

Post-quantum key exchange ciphers (2.18.0)

Quantum computers, once sufficiently powerful, might be able to break classical public-key cryptography such as RSA and elliptic-curve Diffie-Hellman. While large-scale quantum computers don't exist yet, encrypted data captured today could be decrypted in the future — a threat known as "harvest now, decrypt later".

To address this, Buru SFTP Server 2.18.0 adds support for NIST-standardized post-quantum key exchange based on ML-KEM (CRYSTALS-Kyber), used in a hybrid construction alongside classical algorithms. This means the key exchange is secure against both classical and quantum attacks:

• mlkem768x25519-sha256 — ML-KEM-768 combined with X25519
• mlkem768nistp256-sha256 — ML-KEM-768 combined with NIST P-256
• mlkem1024nistp384-sha384 — ML-KEM-1024 combined with NIST P-384

These algorithms are already supported by OpenSSH 9.0+ and other modern SSH clients. See the full list of supported SSH algorithms.

SSH/SFTP core overhaul (2.18.0)

The SSH and SFTP processing core has been significantly redesigned to improve performance and reduce memory and thread usage. These improvements are most noticeable when serving many simultaneous connections.

Elliptic curve algorithm performance has also been improved on modern platforms.

Additional key exchange algorithms (2.18.0)

Two additional Diffie-Hellman key exchange algorithms are now supported, offering stronger security:

• diffie-hellman-group17-sha512
• diffie-hellman-group18-sha512

See the full list of supported SSH algorithms.

copy-data SFTP extension (2.18.0)

Buru SFTP Server now supports the copy-data SFTP extension, which allows clients to request server-side file copies without transferring data over the network. This results in significantly faster copy operations, especially for large files.

Minor changes and fixes

• SSH
  • Improved compatibility with some SSH clients that are sensitive to the order of SSH shell channel messages. (2.18.1)
• FTP
  • Fixed behavior of ftp.bindings[].externalAddress and ftp.bindings[].dataPortRange in FTPS implicit mode. (2.18.2)
• Installer
  • Now checks for a valid license before overwriting the existing installation when upgrading. (2.18.0)
  • Silent uninstallation (/SILENT) no longer prompts for confirmation and deletes all configuration files. (2.17.3)
• Web Admin
  • Log viewer now shows the last 50 kB of the log file, with an option to view or download the full file. (2.18.3)
  • Fixed 2FA status not being indicated correctly for some users. (2.18.0)
  • Fixed an error when saving a user with an SSH public key. (2.17.2)
  • Fixed an incorrect warning message "The WebRootPath was not found". (2.17.3)
  • Log viewer is now accessible even when the configuration file is invalid but readable. (2.17.3)
  • User's virtual path can now be specified without a leading slash. (2.17.3)
  • Improved readability of users' public keys. (2.17.3)
• Other
  • Fixed LiteDB database locking error. (2.18.3)
  • Fixed startup error when sshTunneling is present but disabled in the configuration file. (2.17.1)
  • User authentication method is now logged at information level (previously debug). (2.17.3)
  • Added an error log message when the service starts under the SYSTEM account with defaultShellType: terminal and allowSystemAccount not enabled. (2.17.3)

For a complete list of fixes and improvements, see the Release notes.

You can report issues and submit feature requests on our Github issue tracker.

For discussions and specific problems, please continue using our support forum.