The SSH (Secure Shell) Remote Login Protocol

INTRODUCTION

• SSH (Secure Shell) is a program to log into another computer over a network, to execute commands in a remote machine, and to move files from one machine to another.

• It provides strong authentication and secure communications over insecure networks.

FEATURES

• Closes several security holes (e.g., IP, routing, and DNS spoofing).

• It provides strong authentication and secure communications over insecure networks.

• All communications are automatically and transparently encrypted. Encryption is also used to protect integrity.

• Arbitrary TCP/IP ports can be redirected over the encrypted channel in both directions.

Examples of what SSH can be used for are:

• Access to the UNIX-like environment from a Windows machine.

• Work from home with access to your file store.

• Copying files between your file store and another machine;

• Read restricted web pages

• Other protocols, such as RSH (remote shell) and Telnet, allow computers to communicate in a similar way to SSH. These protocols are now considered insecure .

RLOGIN(INTRODUCTION)

• rlogin is also the name of the application layer protocol used by the software, part of the TCP/IP protocol suite.

• Authenticated users can act as if they were physically present at the computer.

• The rlogin facility provides a remote-echoed, locally flow-controlled virtual terminal with proper flushing of output.

USE

• rlogin is most commonly deployed on corporate or academic networks, where user account information is shared between all the Unix machines on the network .

• rlogin allows logins without password (where rlogin trusts a remote rlogin client) .

SECURITY rlogin has several serious security problems:• All information, including passwords, is transmitted unencrypted

(making it vulnerable to interception).• The rlogin file is easy to misuse (potentially allowing anyone to

login without a password) - for this reason many corporate system administrators prohibit rlogin files and actively search their networks for offenders.

• The protocol partly relies on the remote party's rlogin client providing information honestly (including source port and source host name). A corrupt client is thus able to forge this and gain access, as the rlogin protocol has no means of authenticating other machines' identities, or ensuring that the rlogin client on a trusted machine is the real rlogin client.