SFTP specifications

The SSH File Transfer Protocol (SFTP) is used to transfer files over a cryptographically protected Secure Shell (SSH) connection.

Technical Specifications

RFC 4250 The Secure Shell (SSH) Protocol Assigned Numbers
RFC 4251 The Secure Shell (SSH) Protocol Architecture
RFC 4252 The Secure Shell (SSH) Authentication Protocol
RFC 4253 The Secure Shell (SSH) Transport Layer Protocol
RFC 4254 The Secure Shell (SSH) Connection Protocol
RFC 4255 Using DNS to Securely Publish Secure Shell (SSH) Key Fingerprints
RFC 4256 Generic Message Exchange Authentication for the Secure Shell Protocol (SSH)
RFC 4335 The Secure Shell (SSH) Session Channel Break Extension
RFC 4344 The Secure Shell (SSH) Transport Layer Encryption Modes
RFC 4419 Diffie-Hellman Group Exchange for the Secure Shell (SSH) Transport Layer Protocol
RFC 4462 Generic Security Service Application Program Interface (GSS-API) Authentication and Key Exchange for the Secure Shell (SSH) Protocol
RFC 4716 The Secure Shell (SSH) Public Key File Format
RFC 4819 Secure Shell Public Key Subsystem
RFC 5647 AES Galois Counter Mode for the Secure Shell Transport Layer Protocol
RFC 5656 Elliptic Curve Algorithm Integration in the Secure Shell Transport Layer
RFC 8332 Use of RSA Keys with SHA-256 and SHA-512 in the Secure Shell (SSH) Protocol
RFC 8709 Ed25519 and Ed448 Public Key Algorithms for the Secure Shell (SSH) Protocol
RFC 8731 Secure Shell (SSH) Key Exchange Method Using Curve25519 and Curve448

draft-ietf-secsh-filexfer-00.txt (draft for protocol version 3)
draft-ietf-secsh-filexfer-01.txt (draft for protocol version 3)
draft-ietf-secsh-filexfer-02.txt (draft for protocol version 3)
Version 3 is the most commonly used version of the protocol.
This is the version implemented in OpenSSH since 2001-03-07 ^{[OpenBSD08, line 32]} and the version used by FileZilla ^{[FileZilla17, line 56]}.
draft-ietf-secsh-filexfer-03.txt (draft for protocol version 4)
draft-ietf-secsh-filexfer-04.txt (draft for protocol version 4)
draft-ietf-secsh-filexfer-05.txt (draft for protocol version 5)
draft-ietf-secsh-filexfer-06.txt (draft for protocol version 6)
draft-ietf-secsh-filexfer-07.txt (draft for protocol version 6)
draft-ietf-secsh-filexfer-08.txt (draft for protocol version 6)
draft-ietf-secsh-filexfer-09.txt (draft for protocol version 6)
draft-ietf-secsh-filexfer-10.txt (draft for protocol version 6)
draft-ietf-secsh-filexfer-11.txt (draft for protocol version 6)
draft-ietf-secsh-filexfer-12.txt (draft for protocol version 6)
draft-ietf-secsh-filexfer-13.txt (draft for protocol version 6)