RFC 4251 - The Secure Shell (SSH) Protocol Architecture

Publication Date: January 2006
Status: Standards Track
Authors: T. Ylonen (SSH Communications Security Corp), C. Lonvick, Ed. (Cisco Systems, Inc.)

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Abstract

The Secure Shell (SSH) Protocol is a protocol for secure remote login and other secure network services over an insecure network. This document describes the architecture of the SSH protocol, as well as the notation and terminology used in SSH protocol documents. It also discusses the SSH algorithm naming system that allows local extensions. The SSH protocol consists of three major components: The Transport Layer Protocol provides server authentication, confidentiality, and integrity with perfect forward secrecy. The User Authentication Protocol authenticates the client to the server. The Connection Protocol multiplexes the encrypted tunnel into several logical channels. Details of these protocols are described in separate documents.

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Contents

• 1. Introduction
• 2. Contributors
• 3. Conventions Used in This Document
• 4. Architecture
  • 4.1 Host Keys
  • 4.2 Extensibility
  • 4.3 Policy Issues
  • 4.4 Security Properties
  • 4.5 Localization and Character Set Support
• 5. Data Type Representations Used in the SSH Protocols
• 6. Algorithm and Method Naming
• 7. Message Numbers
• 8. IANA Considerations
• 9. Security Considerations
  • 9.1 Pseudo-Random Number Generation
  • 9.2 Control Character Filtering
  • 9.3 Transport
  • 9.4 Authentication Protocol
  • 9.5 Connection Protocol
• 10. References
  • 10.1 Normative References
  • 10.2 Informative References

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Related Resources

• Official Text: RFC 4251
• Official Page: RFC 4251 DataTracker
• Errata: RFC Editor Errata

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