Re: Encrypted column

On Jun 5, 2007, at 7:28 AM, Ron Johnson wrote:

> On 06/05/07 08:59, Alvaro Herrera wrote:
>> Ron Johnson wrote:
>>> On 06/04/07 17:54, Guy Rouillier wrote:
>>>> Many people consider two-way encryption to be insecure; two-way
>>>> encryption means you can decrypt a value if you know the key,
>>>> and it is insecure because you usually have to put the key into
>>>> the source code. That means at least one person in your company,
>>>> the programmer maintaining the source code, can learn all of
>>>> your users' passwords.
>>> Two-way encryption is needed for companies that store customer
>>> credit cards.
>> I thought that the advice for companies storing customer CCs was:
>> don't.
>
> Sometimes you "must".
>
> An example from my industry: transponder "toll tags" and toll
> roads. The customer pre-pays a certain amount based on expected
> usage, and every time he drives thru a plaza, his balance
> decreases. Once it drops to a certain threshold, more money needs
> to be added to the account.
>
> If he is a CASH/CHEK customer, a light at the lane flashes yellow
> and (depending on the Agency) a message pops up saying, "Balance
> low", so he drives over to the customer service center, stands in
> line and pays his cash.
>
> If he is a CC customer, the system (which I am DBA of) bills his
> card directly, saving the customer much time and effort.

Public key encryption can help here. Encrypt with the public key when
it goes into the database, keep the private key on a separate, well
protected system that's just used for recurring CC billing.

Cheers,
Steve