1.2.1. Secure Shell (SSH)

General

  • Both versions generally use a host-specific key of 2048-bits.
  • Servers that support both SSH Version 1 and 2, usually indicate this by advertising version 1.99 in their connection banner.
  • Minimum of 768-bits for RSA Key

Version 1

  • No defined standard, considered proprietary
  • Ciphers (3DES, Blowfish, DES)
  • Authentication (?)
  • Supports only RSA Keys
  • Forward Security provided through an additional server key, of 768-bits. This is commonly regenerated (e.g. once per hour)
  • Lack of strong mechanism for ensuring integrity of connection

Version 2

  • Initially RFC 4251
  • Incompatible with version 1
  • Minimum of 768-bits for RSA Key
  • Supports DSA, ECDSA and RSA Keys
  • Forward Security provided through Diffie-Hellman (DH) Key Exchange
  • Integrity provided through HMAC (HMAC-HD5, HMAC-SHA1, etc)
  • Multiple supported authentication methods
    • Password
    • Public Key (at least DSA or RSA)
    • Keyboard Interactive / Generic Message Exchange Authentication
    • GSSAPI