Question

SQL joins on encrypted data

Database, Oracle, DB2, Microsoft Windows, OS, Servers, Security, Desktops, Management, SQL Server, Web site design & management

Hi - we are in the process of encrypting various pieces of sensitive information in our SQL 2000 tables. For many fields we are using Blowfish 448 encryption and a concern has arisen about inline SQL statements that contain joins in our ASP scripts. Are there any scenarios that you have run across where there may be a problem with a join of encrypted data? Could there ever be an instance where the encrypted field (encrypted by Blowfish) in one table would be different from the field in another table given the same initial string, which upon executing the join would cause the join to fail?

To be more clear here is a quick example:
Table A has an encrypted account number column. Table B also has an encrypted account number column (same data). If we have a SQL statement that performs a join on the account number columns in the two tables is there any possibility that the join will fail because the Blowfish encryption somehow yielded a different value?

Any thoughts you have would be helpful.

Thanks,
Tim

If your encryption padds the encrypted value with filler data then yes, the join could fail as the values wouldn't match. If you aren't padding the encrypted value then your values should match and you should be able to do the join.