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Rohit Mehta : A Linux Follower

bangalore, Karnataka, India
hi! i m a person who is chill all time. Since jan 2008 i am working for Novell software. The word Impossible does not exist in my dictionary because Impossible says i m possible...hey guys have fun with linux...it begins but has no end......

Tuesday, November 17, 2009

How does SSH(Secure Shell) works


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You must have done remote file sharing and remote logins. Have you ever thought that whether your communication over the channel  is   secure or not. If you are using tools/utilities like ftp , telnet then you are not secure. SSH acronym for Secure Shell enables you to have transfer over the network in the encrypted manner.
This is how SSH works:
When a user attempts for a remote login using SSH ,for the first time it prompts for the generation of keys. SSH uses asymmetric Encryption. Asymmetric encryption also allows for digital certificates.

Two types of key are generated:
Private key : This key is kept only with the user who generated the key and is used for encrypting the messages before sending them over the network.
Public key : This key is distributed to all the users with which you want to encrypt your communication .Remote system uses this key to decrypt the encrypted messsages which is sent by the user to the remote  machines.
This is how SSH actually works:
SENDER:
generate public/private key pair : P and S
 publish public key P .guard private key S
encrypt message M with private key S
 send recipient S(M)
RECIPIENT:
decrypt with sender’s public key to recover M=P(S(M))
For making remote login through ssh :
At the hash prompt:
#ssh 192.168.1.1
then type yes for the generation of the keys and then enter the password for the remote system and you are logged into the system
Enjoy the encrypted communication and stay away from network hacks.

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