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5 – Cell-Level Encryption• User Specific – users can be granted access to keys that encrypt anddecrypt data that is exclusive to their use.The disadvantages of cell-level encryption include:• Data type restrictions – implementation of cell-level encryptionrequires schema modifications. All encrypted data must be stored withthe varbinary data type.• Expensive table scans – due to the nature in which the values areencrypted any referential constraints, primary keys and indexes on datathat is encrypted is no longer used. This results in table scans whenencrypted data is referenced in queries.• Processing overhead – the additional processing required forencrypting and decrypting data has a cost to the overall performance ofthe database.The use of cell-level encryption does present its own unique set of challengesand costs; but these should not dissuade from the consideration of its use.The actual performance impact of cell-level encryption will vary dependingupon the environment in which the database resides. The size of the impact thatcell-level encryption has on the database performance will depend on theserver's hardware, such as load balancing, number of processors and amount ofavailable memory, as well as on non-hardware items such as queryoptimization, index placement and overall database design.In the HomeLending database, we took advantage of normalization to isolateour sensitive data. It is only accessible, through a view, to a select number ofusers that perform decryption. Also, it is through a stored procedure, whichalso is available to a very limited number of users, that the encryption functionsare executed. Thus, the performance impact is much less than if it wereavailable to all users of the database, or if the column remained in a high-traffictable. When cell-level encryption is strategically implemented, it is a veryeffective method of protecting sensitive data at the highest degree ofgranularity.Special ConsiderationsThe consideration of the benefits and disadvantages of cell-level encryption isimportant in the decision to select this method to protect sensitive data.Additionally, there are also some special considerations that are worthy of note:102