The Magento Encryption Key is kept in the app/etc/local.xml file. You can open it through cPanel->File Manager. You can find more details on how to view the file content in our cPanel tutorial.
The code which you should look for is:
<crypt>
<key><![CDATA[ENCRYPTION_KEY]]></key>
</crypt>
The ENCRYPTION_KEY string is replaced by the actual encryption key.
You need it if want to move your store data to a new Magento site. The Encryption key is used to recover the encrypted data.
When you migrate your database content to a new Magento installation, make sure that the encryption key from the existing installation is written in the new web site's local.xml file. Otherwise the encrypted data, stored in the new database will not work.
