Whenever you wanna change the Magento’s Admin password directly in the database or wanna cross check the encrypted password in the db with the plain text password, you need to generate the Salt password hash. In the ‘admin_user’ table of your Magento database, you can find all the admin users password. In those password fields, you can notice the last to characters added to the string after the ‘:'(semi-colon). That is the Salt for your installation.
The password may be seem something like this
In the above case K5 is the salt. If the have the raw password and wanna generate the encrypted password, you can do the following
Where $salt is the last two characters of your encrypted password that you found in the previous step. Since md5 is used for encryption, there is no decryption exist.