Online Security
Q: My Netscape browser is displaying a form for ordering merchandise
from a department store that I trust. The little key at the lower
left-hand corner of the Netscape window is solid and
has two teeth. This means I can safely submit my
credit card number, right?
Not quite. A solid key with two teeth appears indicates that SSL is
being used with a 128-bit secret key and that the remote host owns a
valid server certificate that was certified by some authority that
Netscape recognizes. At this point, however, you don't know who that
certificate belongs to. It's possible that someone has bought or stolen
a server certificate and then diverted network traffic destined for the
department store by subverting a router somewhere between you and the
store. The only way to make sure that you're talking to the company you
think you're talking to is to open up the "Document Information" window
(from the File menu) and examine the server certificate. If the host and
organization names that appear there match the company you expect, then
you're probably safe to submit the form. If something unexpected appears
there (like "Embezzlers R Us") you might want to call the department
store's 800 number.
Q: How secure is the encryption used by SSL?
SSL uses public-key encryption to exchange a session key between the
client and server; this session key is used to encrypt the http
transaction (both request and response). Each transaction uses a
different session key so that if someone manages to decrypt a
transaction, that does not mean that they've found the server's secret
key; if they want to decrypt another transaction, they'll need to spend
as much time and effort on the second transaction as they did on the
first.
Netscape servers and browsers do encryption using either a 40-bit secret
key or a 128-bit secret key. Many people feel that using a 40-bit key is
insecure because it's vulnerable to a "brute force" attack (trying each
of the 2^40 possible keys until you find the one that decrypts the
message). Using a 128-bit key eleiminates this problem because there are
2^128 instead of 2^40 possible keys. Unfortunately, most Netscape users
have browsers that support only 40-bit secret keys. This is because of
legal restrictions on the encryption software that can be exported from
the United States (The Federal Government has recently modified this
policy on following the well-publicized cracking of a Netscape message
encrypted using a 40-bit key. Expect this situation to change).
In Netscape you can tell what kind of encryption is in use for a particular
document by looking at the "document" information" screen accessible
from the file menu. The little key in the lower left-hand corner of the
Netscape window also indicates this information. A solid key with two
teeth means 128-bit encryption, a solid key with one tooth means 40-bit
encryption, and a broken key means no encryption. Even if your browser
supports 128-bit encryption, it mayse use 40-bit encryption when talking
to older Netscape servers or Netscape servers outside the U.S. and
Canada.
Q: My friend says that none of this stuff is safe. What
should I believe?
When credit cards first came out in the late 1960s, the cardholder was
liable for all losses occurring as a result of a stolen card. The
credit card companies soon discovered that fear of large losses prevented
people from using or keeping the cards. For a long time now, you have
been liable (in most states) for at most $50 of loss as a result of
credit card fraud.
Using your credit card on the Internet is no different than giving it to
a restaurant. The presence of a warning-free SSL security system
ensures that the company you are dealing with has passed background
checks -- just like the presence of a Verifone credit-card checking device
gives a good indication that the restaurant can actually accept credit
cards. Look for a server certified by Verisign, Thawte, or another
well-known certifying agency. If a server's SSL certificate is so signed,
you have done your job to verify authenticity.
We don't recommend that you send your credit card number un-encrypted
over the Internet. Just like you know not to give your card number to
anyone who calls you -- you make sure you know who you are talking to
first -- you shouldn't send your card number over the Internet until
you are certain that the company you are dealing with has made the effort
to ensure security. Presence of a warning-free SSL security system
indicates that rather considerable effort has been made. Look for the
lock, key, or blue line, and you should be safe.
Q: Yes, all that is fine, but what about your software? Won't
the number stick around on the disk forever?
The SSL encryption will take care of network transmission. But we
don't want to make it easy for just anybody, even those with access
to our system, to view your number. Your credit card number is encrypted with
GPG (GNU Privacy Guard) encryption before ever being briefly
written to a file during processing of your order.
First of all, after you enter your number, it is kept in memory only until
until it is encrypted. At that time, it is scrubbed from the program's
memory. The now-encrypted card number (with the password only known
to our order entry personnel) is then written to a file with
permissions set so only the program can get at it.
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