In my company there is MS SQL SERVER 2008 standard edition installed. My problem is we want to encrypt whole database but in standard edition there is encryption like transparent-data-encryption(TDE) not available and column level encryption is time consuming. So i want to know is there any alternative method available in sql server gor whole database backup?
For encrypting data files at rest, you can use a third party product called NetLib Encryptionizer for SQL Server that basically does TDE through a filter driver.
For encrypting backups, you can use any number of third-party backup products. The most popular ones in alphabetical order are Idera SQL Safe, Quest Litespeed, and Red Gate SQL Backup - all of which can encrypt backups on any version/edition of SQL Server that they support. I've also seen cheaper ones, but I'd just caution you that you should only use backup products that have 24/7 support available. Don't play around with restores.
I have no affiliation with any of those products. (I used to work for Quest.)