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Friday, December 1, 2017

SSH Key Gen & SSH Keys on windows system to Linux Server

SSH Key Gen & SSH Keys on windows system to Linux Server 

     ssh-keygen - authentication key generation, management and conversion

ssh-keygen generates, manages and converts authentication keys for ssh.  ssh-keygen can create RSA keys for use by SSH protocol version 1 and DSA, ECDSA or RSA keys for use by SSH protocol version 2. The type of key to be generated is specified with the -t option.  If invoked without any arguments, ssh-keygen will generate an RSA key for use in SSH protocol 2 connections.

SSH Key Generation:

[nsk@nsk-linux ~]$ ssh-keygen
Generating public/private rsa key pair.
Enter file in which to save the key (/home/nsk/.ssh/id_rsa):      - Just give enter
Enter passphrase (empty for no passphrase):                           - Dont give passphrase
Enter same passphrase again:               
Your identification has been saved in /home/nsk/.ssh/id_rsa.
Your public key has been saved in /home/nsk/.ssh/
The key fingerprint is:
ae:67:71:78:9e:b5:31:1e:bb:7b:c7:0a:3b:18:0b:c8 nsk@nsk-linux
The key's randomart image is:
+--[ RSA 2048]----+
|                 |
|                 |
|                 |
|                 |
|     . .S.       |
|      E.+ + =    |
|        .* B.* . |
|       .o = =o. o|
|      .o    +=.o |

[nsk@nsk-linux ~]$ cd .ssh/
[nsk@nsk-linux .ssh]$ ls -al
total 48
drwx------  2  nsk  nsk  4096 Dec  1  10:08 .
drwx------ 37 nsk  nsk  4096 Nov 26 09:51 ..
-rw-------  1   nsk  nsk  1675 Dec  1  10:08 id_rsa
-rw-r--r--  1   nsk  nsk   395 Dec  1   10:08
-rw-------  1   nsk  nsk  8594 Nov  7   08:23 known_hosts

We need to convert id_rsa key (windows to linux) for successful password less authentication from windows system

1. Save the id_rsa key in Windows system
2. Use Putty Key Generator tool & click the conversions
3. Click Import Key & Browse the id_rsa key
4. Click Save Private Key. Once pop up comes, click save the key without a passphrase on local system.

5. Copy key to /home/nsk/.ssh/authorized_keys  (change the user home directory)
[nsk@nsk-linux .ssh]$ cat >> /home/nsk/.ssh/authorized_keys
[nsk@nsk-linux .ssh]$ cat authorized_keys
ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAQEAv4ZERTCXFpGZLrNKBOQfiTE5SEQYvtiolNt8KnMVY9bxwEUMyPUX9EwmJxW51BY8I9Xq6VGoU2nskS0GrTgqjAOeptTRia0ws7inkc9oHVHryqJdgvhYvpVj2lLsnRTO9Lv4P6Pkycvg5xioAKRTdL8EffPxWtu8x1iL6aYsHThxsrpmXzK0LrkHLnGsJT5nRtNOWlUJW9npNPRBSqRmPjFCRpWb2kgn7MUKJnr5rXA2kgrULCvx97EFDxA/HYAxFgld7yGdnPjdZWyrkXK/FsFmsU4xoGoSNVKG1Vq1R18rc/cNjtVPME9TBxD8OBB8FQYiyHLYWLF+x9EbGsY+lQ== nsk@nsk-linux

6.  Here .ssh should be 0700 permission and authorized_keys should be 0600 permisssion.

7.  Open putty tool - Enter the Server IP in session ==> expand the SSH ==> select AUTH and browse the key ==> Select the key

8. Give username & enter. Here Putty session wont ask password.

Hope it helps.

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