Encrypted data size by original size, algorithm ?

I want to know encrypted data's size for designing database field size.

For example, cardnumber varchar(20) Encrypted by Triple_DES and PassPhrase, How match size does need to encrypted data store field.

I think the size does not depend to PassPhrase char length.

Regards,
Yoshihiro Kawabata

The simplest way is to just encrypt the largest piece of data that you will store using the encryption algorithm of your choice and take note of the size of the resulting blob. That will be the size of the field. There is also a formula that allows you to compute this, but it also includes the size of a header which might expand in future versions of SQL Server. I suggest to always leave several bytes more to account for changes in the format of encrypted data.

Thanks
Laurentiu

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Here's a post that describes how to determine the length of the encrypted data for SQL Server 2005:

http://blogs.msdn.com/yukondoit/archive/2005/11/24/496521.aspx

Thanks
Laurentiu