[AccessD] Field Level AES Encryption

How do you create the hash - any generator to recommend?
Asger
-----Oprindelig meddelelse-----
Fra: accessd-bounces at databaseadvisors.com [mailto:accessd-bounces at databaseadvisors.com] På vegne af jwcolby
Sendt: 28. april 2011 22:10
Til: Access Developers discussion and problem solving
Emne: Re: [AccessD] Field Level AES Encryption

Unless you actually need the ssn, I recommend storing a HASH of the ssn.  Then you when you need to 
see if the SSN entered in a form somewhere is equal to the SSN you "stored", you hash the SSN 
entered and compare to the hash you stored.  You never have the ssn stored at all and the hash is 
one way so it can't be deduced.

John W. Colby
www.ColbyConsulting.com

On 4/28/2011 1:00 PM, jm.hwsn wrote:
> I thought I would send this information to this group, especially since
> Philippe Pons asked the question about hiding information.
>
> I had a requirement to encrypt a single field within a database.  This field
> contains the Social Security Number (SSN) of the users of the database.  The
> SSN is used as an individual's password and by government standards MUST be
> encrypted.
>
> After much searching and testing different suggestions, I found a solution.
> It involves a Class and a module and uses the American Encryption Standard
> (AES) developed by Joan Daemen and Vincent Rijmen hence call Rijndael.
>
> The class was written in 2001 by Phil Fresle and works flawlessly.  I don't
> understand how it works nor would I even attempt to change it.
> The original code was written in C.  The Class was written for VB6 but works
> in VBA without modifications.  Fresle is from the UK. his website is:
> www.frez.co.uk/ On his website is the latest version of the Class.
>
> But, I found the best solution which incorporates Mr. Fresle's class on an
> Excel Website by Dermot Balson from Australia.
> His website is:  http://www.westnet.net.au/balson/ModellingExcel/VBA.shtml
> Mr. Balson by his own admission is "an actuary who loves working in Excel."
> The class on Mr. Balson's site needs to be updated with the latest version
> from  Mr. Fresle's site.
>
> What I like about Mr. Balson's solution is that the module contains two
> functions.  One to encrypt the field and the other to decrypt the data.
> Also,  changing from 128 bit to 192 or to 256 bit encryption is simply
> changing a public KeyLength.  The results are stored in a table in pure
> ASCII so it's easy to use the ASCII key if needed.
> What I didn't like was the PassPhrase (password) was required for each
> function and the decryption of the data left blank spaces at the end.
>
> So I modified the module by creating a function for the password. of course
> it's hidden in the module and password protected through Access' encryption.
>
> Now I can change the PassPhrase in one place and change the encryption key
> size at anytime. And if needed, I can use the password field as text.
>
> Life if good!
> HTH
> Jim
>
>
>
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