Download PuTTYgen ( http://www.chiark.greenend.org.uk/~sgtatham/putty/download.html ), open it and select SSH2-DSA at the bottom of the main window. Then click “Generate”. The program will ask you to move the mouse over the blank area to generate randomness.
Once the key has been generated, export it by opening “Conversions” menu and select “Export OpenSSH key”. Don’t use any passphrase when exporting it, so click “No” if a warning dialog appears. This will export the private key, which you must save as “id_dsa”. To export the public key, in the main window of PuTTYgen you can see a text box on the top which title is “Public key for pasting into OpenSSH authorized_keys file”. Select all the text in the box and copy it in the clipboard.
Create a text file with notepad editor and paste the text into the file. Save the file and close notepad. Rename this file to “id_dsa.pub” and that’s all.