Monday, November 06, 2006


A compressed and encrypted User Defined Type (UDT) for SQL Server 2005

Compression and encryption: you may like or hate them, but they have been (and will be) there for a long time.

In fact, there are so many resources devoted to compression and encryption that is difficult to believe anyone could have a requirement and nobody has already developed a solution for that requirement.

Well, this is not totally true. For example, related to compression, time ago I had to develop a tool to perform on-the-fly compression/decompression for the output/input of windows programs (something similar to Unix tool mknod, but as a native Windows application, not emulated with Cygwin or similar).

Now, although the built-in support for Encryption in SQL Server 2005 seems to be enough to solve almost any encryption requirement at database level, I miss one feature: a native encrypted text data type that could be used as any other native data type in table definition.

I won’t discuss here whether it is necessary or not to have this data type or if it is better to satisfy this requirement using other techniques. This is better done by Sybase in its product features sheet ( or search for the words column and encryption in site if the previous link becomes broken).
I know at least Sybase and Oracle 10g R2 are at this moment offering transparent data encryption at column level.

So, I started thinking how it could be done in SQL Server 2005. Many fancy features came to my mind during this phase, however, I tried to simplify as much as possible while keeping an interesting level of functionality for the this UDT. These are some of the features implemented in the Compressed and Encrypted UDT:

If you want to see a demo about how to create and use this compressed and encrypted UDT read this article:

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