On Sun, May 30, 2010 at 2:16 AM, Ashley Sheridan <ash@xxxxxxxxxxxxxxxxxxxx>wrote: > On Sun, 2010-05-30 at 01:49 -0400, Paul M Foster wrote: > > > This question is for people who take and store credit card information > > for customers. > > > > Credit card companies, in an attempt to lessen fraud, are tightening the > > screws on merchants who take credit cards. One aspect of this is a > > requirement to store credit card information from customers encrypted. > > > > So let's say you have a customer whose credit card you keep on file, > > because they'll be charging other items with you. The credit card > > companies would like you to store this information with strong > > encryption, which in their mind is one-way encryption. > > > > Now let's say that the credit card number is part of the customer > > record. When looking at the customer record, you see just the last four > > digits of the card. But when editing the record or when printing out > > reports of things which must be charged, you will see the whole number. > > Assume the users of the system have logins and passwords. > > > > Now if you one-way encrypt the credit card numbers in the customer > > records, then it seems to me that any time that field has to be accessed > > (to edit the record or charge something to the card), you'd have to have > > the user enter a specific "password" to unlock the encryption. This > > would be quite in addition to their username and password. Moreover for > > this to be as secure as the credit card companies would like it, > > whatever "password" is used would need to be changed frequently, > > particularly at any change of personnel. This means you'd have to > > re-encrypt all the credit card numbers using the new "password" every > > few months or when you fire someone who had access to the data. > > > > This seems like an excessively cumbersome solution. Is this seriously > > the way it's done? Does anyone have a better solution? > > > > > > Paul > > > > -- > > Paul M. Foster > > > > > It's not just a matter of encrypting the credit card details. You also > have to ensure the server meets specific security requirements, every > last little bit of software has to be updated and patched. There are > services that will check your server out for you (last one I used was > McAffee Secure) I am certain that this is a legal requirement in order > to allow you to process credit card details. > > You won't have to encrypt the password against the username of whoever > has access to it. Just encrypt it the once, and use the DBMS side of > things to manage access rights. Maybe use a couple of fields in the DB > to store the credit card number in two versions, one that is two-way > encrypted, the second that is one-way. You can set up your web system to > only have access to the one-way version, meaning that the actual number > can't be got by that user. The two-way encrypted version would be > accessible only by a specific second DB user, the access details of > which could change when personnel changes. > > Thanks, > Ash > http://www.ashleysheridan.co.uk > > > Hi Paul, When you describe one-way or two-way encryption, what are you describing? Are you describing hashing vs encryption where the plain-text is recoverable with a key, or are you describing symmetric (one key handles encrypting and decrypting) vs asymmetric (separate keys handle encrypting and decrypting) encryption? Now if you one-way encrypt the credit card numbers in the customer records, then it seems to me that any time that field has to be accessed (to edit the record or charge something to the card), you'd have to have the user enter a specific "password" to unlock the encryption. You can't decrypt (or "unlock") a hashed password (at least if you used a secure hash), but I'm not sure you're talking about symmetric vs asymmetric encryption, either. With more details , I can provide feedback on the encryption schemes you're considering (remember, you have to make sure that you are managing encryption keys very carefully, as among other things, PCI requires that "keys are stored in encrypted format and that key- encrypting keys are stored separately from data- encrypting keys.") However, I'd strongly recommend letting a payment gateway do the heavy lifting. You let the payment gateway store the credit card details, and when you want to process another transaction for a visitor, you use the id for the visitor that's stored in your DB (if they already have set up an account) to process the request. For example, this type of scheme is documented at Rackspace (PDF): http://cloudsites.rackspacecloud.com/index.php/Can_I_host_a_PCI_compliant_site_on_Cloud_Sites%3F Adam -- Nephtali: PHP web framework that functions beautifully http://nephtaliproject.com
