Data encryption and decryption in sql server 2005

Also, if you plan to encrypt data and write it on a table or store encrypted data in a stored procedure or in a user defined function udf , you can open the related symmetric key once at the beginning of the stored procedure or user-defined function t-sql codes, and then in the following lines of sql codes you can execute the EncryptByKey and the DecryptByKey Transact-SQL commands. As well as encrypting, decrypting can be handled using t-sql commands and functions in SQL Server.

DecryptByKey t-sql function decrypts data using a symmetric key definen in the current sql database. You can call the DecryptByKey function passing the encrypted data in varbinary data type. Just as similar to EncryptByKey requires an opened symmetric key in the current session, DecryptByKey function also requires a symmetric key that has been opened in the current session before it is called.

One last important point for decrypting encrypted data on SQL Server is that as a sql programmer or administrator, you should take care for the original data type that is encrypted and the target data type that the decrypted data is going to be converted. Since DecryptByKey function returns data in varbinary data type up to bytes, if you convert this decrypted varbinary data to nvarchar sql data type you get different result when compared to decrypted varbinary data converted to varchar.

So, if you are encrypting nvarchar data, decrypt and convert it back to nvarchar. Same for varchar data type also. Otherwise, you will not get expected results from implemented decryption algorithm. Let's look at the following select script where encryption and decryption takes place for both varchar and nvarchar data types.

You will see if nvarchar data is converted back to nvarchar then result is correct. Same is true for also varchar data. I have used string values or database table column names in the previous examples. But sql variables can also be used for encryption and decryption functions. Encryption and Decryption is an important aspect for database security in sql database development. Development resources, articles, tutorials, code samples, tools and downloads for ASP.

This might be good enough for passwords and the like, but for credit card and Social Security numbers, you had a problem. So you have to write Transact-SQL scripts for these features. As this is a completely new area for SQL Server , there are many things that we can discuss.

Rather than loading all the functionalities into a single article, I have written two. This first article will provide an overview of data encryption, service master keys, and database master key management. The next article will discuss the implementation of encryption with certificates, symmetric keys, and asymmetric keys. The following image shows that there are three ways to encrypt your data. I will this describe the pros and cons of those methods in the next article.

As you can see from the above image, the SMK is the root of all the encryptions. Because of that, they say it is the mother of all SQL Server encryption keys. SMK is a symmetric key. A Symmetric key is used for both encryption and decryption.

You can regenerate the SMK, but as it is the root of the SQL Server encryption hierarchy, it involves decrypting and re-encrypting the complete hierarchy. As you can imagine it is a resource intensive operation and should be scheduled at off-peak load times. For both functions, you need to supply the ID of the certificate. If a certificate is encrypted with a password, you need to provide the password when decrypting it.

You can find all the information for a certificate in the sys. A Symmetric Key is a one key that is used for both encryption and decryption. This is a fast, commonly used method for encryption. As with a certificate, many parameters are available when creating Symmetric Keys. In most cases, we only need a limited set of parameters. You can refer to Books Online for all the parameters.

You can specify an encryption algorithm for a symmetric key. AES encryption algorithms are currently supported only on Windows If you try to use an AES encryption algorithm, you will get an error:. Either no algorithm has been specified or the bit length and the algorithm specified for the key are not available in this installation of Windows.