Securely storing and searching by social security number

Question

So I\'m working on a supplemental web-based system required by an HR department to store and search records of former personnel. I fought the requirement, but in the end it was

Answer 1

I've had to solve a similar problem recently and have decided to use an HMAC for the hashing. This would provide more security than a simple hash, especially as you can't salt the value (otherwise it wouldn't be searchable).

Then as you say, use AES with a random salt for the reversible encryption.

It maybe that you don't need to encrypt this data but I had no choice and this seemed like a reasonable solution.

My question on IT Security https://security.stackexchange.com/questions/39017/least-insecure-way-to-encrypt-a-field-in-the-database-so-that-it-can-still-be-in