PHP and MySQL Web Development 4th Ed-tqw-_darksiderg

348 Chapter 15 E-commerce Security Issues
Poor Testing
Testing for all possible input conditions, on all possible types of hardware, running all
possible operating systems with all possible user settings is rarely achievable.This situation
is even more true than usual with web-based systems.
What is needed is a well-designed test plan that tests all the functions of your software
on a representative sample of common machine types. A well-planned set of tests should
aim to test every line of code in your project at least once. Ideally, this test suite should
be automated so that it can be run on your selected test machines with little effort.
The greatest problem with testing is that it is unglamorous and repetitive. Although
some people enjoy breaking things, few people enjoy breaking the same thing over and
over again. It is important that people other than the original developers are involved in
testing. One of the major goals of testing is to uncover faulty assumptions made by the
developers. A person who can approach the project with fresh ideas is much more likely
to have different assumptions. In addition, professionals are rarely keen to find flaws in
their own work.
Repudiation
The final risk we will consider is repudiation. Repudiation occurs when a party involved
in a transaction denies having taken part. E-commerce examples might include a person
ordering goods off a website and then denying having authorized the charge on his
credit card, or a person agreeing to something in email and then claiming that somebody
else forged the email.
Ideally, financial transactions should provide the peace of mind of nonrepudiation to
both parties. Neither party could deny their part in a transaction, or, more precisely, both
parties could conclusively prove the actions of the other to a third party, such as a court.
In practice, this rarely happens.
Authentication provides some surety about whom you are dealing with. If issued by a
trusted organization, digital certificates of authentication can provide greater confidence.
Messages sent by each party also need to be tamperproof.There is not much value in
being able to demonstrate that Corp Pty Ltd sent you a message if you cannot also
demonstrate that what you received was exactly what the company sent. As mentioned
previously, signing or encrypting messages makes them difficult to surreptitiously alter.
For transactions between parties with an ongoing relationship, digital certificates
together with either encrypted or signed communications are an effective way of
limiting repudiation. For one-off transactions, such as the initial contact between an
e-commerce website and a stranger bearing a credit card, they are not so practical.
An e-commerce company should be willing to hand over proof of its identity and
a few hundred dollars to a certifying authority such as VeriSign (http://www.
verisign.com/) or Thawte (http://www.thawte.com/) to assure visitors of the company’s
bona fides.Would that same company be willing to turn away every customer who was
not willing to do the same to prove her identity? For small transactions, merchants are