Re: [PHP] Storing Social Security Number WAS: Encryption/Decryption Question

At 10:56 AM -0400 8/12/10, Bastien Koert wrote:
>However, the data must be stored in an encrypted format and it must be
>transmitted via SSL. We do it that way (taking both a hash for
>searching for the ssn and the encrypted form) and haven't had any
>issues as yet.

The data will be encrypted and only accessible behind an SSL via an 
authorization process -- that's given.

I have given some thought about searching the database for encrypted 
SS#'s and have been perplexed as how to do that.

For searching standard fields, it's a piece of cake to use %LIKE%. 
For example, let's say the investigator has a piece of paper that has 
the number "393" on it and want's to search the database for all 
phone numbers that contain "393" -- he could use %LIKE% and that 
would produce 517-393-1111, 393-123-4567, 818-122-4393 and so on. 
That's neat!

However, if the field is encrypted, then how do you preform a partial 
search on that? You can't encrypt the search string and use that 
because you need the entire string. So, how do you solve that problem?

If you hash the number of store the hash, then you can create a 
hashed search string and use that. But again it doesn't work for 
partial %LIKE% searches. For example, I couldn't search for "393" in 
a SS# -- I would have to search for the complete SS#.

So, how do you solve the %LIKE% problem with encryption and hashes?

>The other thing to consider is that more and more states are looking 
>to encrypt PII data
>(name, dob, ssn etc) for more security.

I'm considering that as well, but that also raises more searching 
problems as described above.

>You could consider storing just the encrypted ssn and link data in a
>separate database, that would require a different logon to access when
>the data is required.

Interesting -- I might also hash the foreign link. But I have to 
think about that.

Cheers,

tedd
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