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Question: How do I protect sensitive data in the database?
Answer:
If you need to protect data in a database that is accessed by multiple Web servers, you need to encrypt the data with a strong symmetric encryption algorithm and protect the encryption key with DPAPI.
To encrypt sensitive data in a database accessed by multiple servers in a Web farm:
* Use a strong symmetric encryption algorithm such as 3DES or AES.
* Use the
System.Security.Cryptography.RNGCryptoServiceProvider class to generate a strong (192 bit, 24 byte) encryption key. Back up the encryption key, and store the backup in a physically secure location.
Note: Cryptographically, 3DES keys are effectively 168 bits in length rather than 192 bits. This is because in each of the three DES applications, a 56 bit key is used even though the block size is 64. The remainder of the 8 bits were meant to be parity bits but were never really used for that purpose. 3DES therefore, uses three times 56 or 168 bit keys.
* Use DPAPI to encrypt the symmetric encryption key on each Web server and store it in a secured registry key. Create an ACL to protect the registry key that allows full control for administrators and read only access for your ASP.NET process account.
To encrypt data and decrypt data, retrieve the encrypted symmetric encryption key from the registry, use DPAPI to decrypt the key and then use the
System.Security.Cryptography.TripleDESCryptoServiceProvider class with the encryption key to either encrypt or decrypt the data stored in the database.
With this process, if the DPAPI account used to encrypt the encryption key is damaged, the backup of the 3DES key can be retrieved from the backup location and be encrypted using DPAPI under a new account. The new encrypted key can be stored in the registry and the data in the database can still be decrypted.
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