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Townsend Security Data Privacy Blog

IBM i FIELDPROC Surprises

Posted by Patrick Townsend on Nov 1, 2011 8:12:00 AM

IBM i automatic encryptionIn V7R1 of the IBM i (iSeries, AS/400) operating system, IBM introduced support for automatic, column-level encryption in the DB2 database call FIELDPROC (short for “Field Procedure”). For customers who are familiar with other automatic database encryption implementations such as Microsoft SQL Server Extensible Key Management (EKM) and Oracle Transparent Data Encryption (TDE), the new DB2 database implementation can be confusing. The encryption implementation in DB2 is quite different from other vendor implementations. Here are a few highlights of those differences:

FIELDPROC is not encryption, it is an exit point. What IBM is providing with FIELDPROC is the opportunity for you, the customer, to implement encryption at the column level. You have to enable the option, provide the IBM i AES encryption software, and do the implementation yourself. This is different from SQL Server and Oracle TDE where the database does the encryption for you.

Operations are on encrypted data. In SQL Server and in Oracle, the database is decrypted and then the SQL operations take place on the plaintext values. Not so in DB2 FIELDPROC. The necessary information is first encrypted, and the operation takes place using the encrypted value. This can lead to some surprises if you are not careful about your approach to AES encryption and Initialization Vectors.

Decryption might not be called on a read operation.  Some IBM i customers are surprised that FIELDPROC may not be called when doing a “read equal” type of operation. In SQL this can happen in a SELECT clause with a WHERE statement. In the RPG language this can be a CHAIN operation with a key value. The DB2 database will call the FIELDPROC application to encrypt the search value, but not call the FIELDPROC application if the search is satisfied. That will defeat your attempt to do data masking on decryption!

Database joins need special care. Database joins take place on the encrypted values, not the decrypted values. This means that identical values in different tables need to have the same encrypted value. This runs counter to normal encryption thinking in database tables.

FIELDPROC applications are dynamic calls.  The FIELDPROC applications that you or your vendor creates are going to be called dynamically from the database engine. This means that when you develop the FIELDPROC application you have to take special care that they perform exceptionally well, and that your encryption library is optimized (see next item).

Not all AES encryption libraries are equal. There are big performance differences between AES encryption libraries and it can mean a really big difference to your FIELDPROC application performance. We’ve noted before that AES encryption library performance can vary by a factor of 116. That difference can mean a batch job that takes 10 hours or 10 minutes. Be careful!

For further information view our webinar "Automatic Encryption on IBM i V7R1" and learn how Automatic Encryption is now possible on IBM V7R1 with AES/400.

Patrick

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Topics: IBM i, automatic encryption, V7R1, AES Encryption

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