Planning Audit Trail database table question

We were asked by our security team to verify that data at rest in our Planning application didn't need to be encrypted specifically related to employee information.  We have a SQL back end for our Essbase cube for Planning.  We were originally told by our support vendor that we shouldn't need data at rest encryption since the data stored in Essbase could not easily be extracted with data and metadata.  That was until he noticed that we had the audit trail feature was turned on. 

Has anyone dealt with attempting to encrypt a single column in the HSP_AUDIT_RECORDS table?  We thought about encrypting the ID2 column that appears to contain the employee ID that could then be referenced to determine the actual employee.  I'm unsure how Hyperion/Essbase will react to this encryption.  I'm guessing it will break the application, but thought I'd check.