Transferring using Secure FTP

You can transfer files with encryption using FTPS in Explicit mode (FTPES) for the connection with the file transfer destination server.

Setting secure FTP transfer

For secure FTP transfer, set [Using Secure Protocol] to [On] in the file transfer destination server settings and import a certificate.

Precautions related to the FTP function

In FTP, the contents, user name, and password are not encrypted. For secure data transfer, use FTPES (FTPS).

About the FTPS function

The FTPS function supports various encryption algorithms to ensure secure file transfer. Multiple encryption algorithms, some of which may not comply with current security best practices, are supported for compatibility with a wide range of servers.

Encryption algorithms supported by the FTPS function

The following encryption algorithms are supported.

  • TLS_RSA_WITH_AES_256_CBC_SHA256
  • TLS_RSA_WITH_AES_128_CBC_SHA256
  • TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
  • TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384
  • TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
  • TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256
  • TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384
  • TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384
  • TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256
  • TLS_DHE_RSA_WITH_AES_256_GCM_SHA384
  • TLS_DHE_RSA_WITH_AES_256_CBC_SHA256
  • TLS_DHE_RSA_WITH_AES_256_CBC_SHA
  • TLS_DHE_RSA_WITH_AES_128_CBC_SHA256

Recommended encryption algorithms

The following encryption algorithms are recommended based on the NIST recommendations (NIST SP 800-57 Part 1 Revision 5) and related security standards.

  • TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
  • TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
  • TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384

About deprecated algorithms

The FTPS function also supports the following algorithms for compatibility, but they are deprecated based on the NIST recommendations (NIST SP 800-57 Part 1 Revision 5) and related security standards, and may be removed in a future version.

  • TLS_RSA_WITH_AES_256_CBC_SHA256
  • TLS_RSA_WITH_AES_128_CBC_SHA256
  • TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384
  • TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256
  • TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384
  • TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256
  • TLS_DHE_RSA_WITH_AES_256_GCM_SHA384
  • TLS_DHE_RSA_WITH_AES_256_CBC_SHA256
  • TLS_DHE_RSA_WITH_AES_256_CBC_SHA
  • TLS_DHE_RSA_WITH_AES_128_CBC_SHA256

About connection compatibility

The FTPS function is designed with a balance between security and compatibility. Currently, deprecated algorithms are supported for the following reasons, but they may be removed in a future version to improve security.

  • Freelance photographers and videographers need to connect to servers running on various clients.
  • Compatibility with older systems and legacy servers needs to be maintained.
  • Not all users are prepared to change to a more secure setting because changing the encryption algorithm settings on the server side is complicated.
  • The FTPS settings are often shared with other secure services. Any changes must be considered carefully as they may have an impact on other services on the server.
  • A wide range of encryption algorithms must be supported to ensure interoperability in different environments.

The encryption algorithm used during an FTPS connection is determined by automatic negotiation with the destination server, and therefore depends on the server settings. While aware of the security risks, compatibility is currently prioritized to satisfy the diverse needs of users.

Security risks

Using deprecated algorithms, including CBC/DHE/RSA/SHA-1, increases the risk that encrypted data may be decrypted or tampered with by an attacker, exposing data during transfer.

Recommendation for secure connection

Before using the FTPS function, check that the connection destination server supports the recommended encryption algorithm. Enable only the recommended algorithms on the server side and disable the deprecated algorithms.

References

  • Recommendation for Key Management, Special Publication 800-57 Part 1 Revision 5, NIST, 2020.
  • Transitioning the Use of Cryptographic Algorithms and Key Lengths, Special Publication 800-131A Revision 2, NIST, 2019.
  • Recommendation for Block Cipher Modes of Operation: The CMAC Mode for Authentication, Special Publication 800-38B, NIST, 2005 (includes updates as of 10/06/2016).
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