FTPä

FTPä is an experimental extension of the File Transfer Protocol (FTP) that adds authentication, encryption, and data integrity while preserving the familiar FTP command set. It appears in academic proposals and prototype implementations but has no formal standard and is not widely deployed. The design aims to improve security without a complete overhaul of FTP infrastructure, by enabling a secure mode through capability negotiation during the initial handshake.

In secure mode, the control and data channels are protected with modern cryptography, with mutual authentication via certificates and per-transfer integrity checks. The protocol emphasizes incremental deployability, preferring negotiation-based upgrade over mandatory changes to existing clients.

Operation and compatibility: FTPä preserves passive and active data connection concepts but encrypts the channels; it supports compatibility mode to allow fallbacks to plain FTP when peer support is absent. Resuming transfers and directory listings are retained, with added integrity verification.

Status and adoption: limited to experimental implementations; there is no widely accepted standard. Interoperability remains restricted to test environments, and misconfiguration can undercut security gains.

Relation to other protocols: FTPä sits conceptually between FTPS (FTP over TLS) and SFTP (SSH-based file transfer). It aims to retain FTP's verb-based interface while adding security, but it has not gained the level of maturity seen in FTPS or SFTP, and real-world deployment remains scarce.