Encrypting SQL Server data
When you're storing sensitive data on your SQL Server, you may need to encrypt the data to protect the data from accidental misuse. There might be your company's business and technical requirements to encrypt the data or even law requirements to encrypt any sensitive information.
SQL Server has many options on how to protect the data with encryption--depending on the need to protect the data at rest or in transit. The whole encryption ecosystem in SQL Server is quite complex and offers many options:

Transparent data encryption
One of the options on how to encrypt the data in the database is transparent data encryption. This feature is available since SQL Server 2008 and works on the I/O level. Both file types--data and log--are encrypted on the disk and SQL Server does the encryption once the data is written to disk and decryption once the data is retrieved from the disk into memory. This encryption works on the page level and does not have an effect on the size of...