Questions about SSL.

Question

Hi

I have a couple questions about SSL certificates.

I never used them before but my current project requires me to do so.

Question 1.

Where should you use SSL? Like I know places like logging in, resetting passwords are definite places to put it. How about once they are logged in? Should all requests go through SSL even if the data in there account is not considered sensitive data? Would that slow down SSL for the important parts? Or does it make no difference?(sort of well you got SSL might as well make everything go through it no matter what).

Question 2.

I know in smtp you can enable SSL as well. I am guessing this would be pretty good to use if your sending say a rest password to them.

If I enable this setting how can I tell if SSL if it is working? Like how do I know if it really enabled it? What happens if the mail server does not have SSL enabled and your have that boolean value enabled. Will it just send it as non SSL then?

Answer 1

Use SSL for any sensitive data, not just passwords, but credit card numbers, financial info, etc. There's no reason to use it for other pages.

Some environments, such as ASP.NET, allow SSL to be used for encryption of cookies. It's good to do this for any authentication or session-ID related cookies, as these can be used to spoof logins or replay sessions. You can turn these on in web.config; they're off by default.

ASP.NET also has an option that will require all authenticated pages to use SSL. Non-SSL requests get tossed. Be careful with this one, as it can cause sessions to appear hung. I'd recommend not turning on options like this, unless you really need them.

Sorry, can't help with the smtp questions.

Answer 2

First off, SSL is used to encrypt communications between client and server. It does this by using a public key that is used for encryption. In my opinion it is a good practice to use it for as anything that has personally identifiable information or sensitive information. Also, it is worth pointing out that there are two types of SSL authentication:

• One Way - in which there is a single, server certificate - this is the most common
• Two Way - in which there is a server certificate and a client certificate - the client first verifies the server's identity and then the server ids the client's id - example is DOD CAC

With both, it is important to have up to date, signed, certificates by a reputable CA. This verifies your site's identity.

As for question 2, yes, you should use SSL over SMTP if you can. If your emails are routed through an untrusted router, they can be eavesdropped if sent without encryption. I am not sure about the 'boolean value enabled' question. I don't believe setting up SSL is simply as easy as checking a box though.

Answer 3

A couple people have already answered your Question 1.

For question 2 though, I wouldn't characterize SMTP over SSL as protecting the message. There could be plenty of points at which the message is exposed. If you want to protect the message itself, you need S/MIME, or something similar. I'd say SMTP over SSL is more useful for protecting your SMTP credentials, so that someone cannot grab your password.

Answer 4

With an SSL connection, one of the most expensive portions (relatively speaking) is the establishment of the connection. Depending on how it is set up, for example, it might create an ephemeral (created on the fly) RSA key for establishing a session key. That can be somewhat expensive if many of them have to be created constantly. If, though, the creation of new connections is less common (and they are used for longer periods of time), then the cost may not be relevant.

Once the connection has been established, the added cost of SSL is not that great although it does depend on the encryption type. For example, using 256-bit AES for encryption will take more time than using 128-bit RC4 for the encryption. I recently did some testing with communications all on the same PC where both client and server were echoing data back and forth. In other words, the communications made up almost the entire cost of the test. Using 128-bit RC4 added about 30% to the cost (measured in time), and using 256-bit AES added nearly 50% to the cost. But remember, this was on one single PC on the loopback adapter. If the data were transmitted across a LAN or WAN, then the relative costs is significantly less. So if you already have an SSL connection established, I would continue to use it.

As far as verifying that SSL is actually being used? There are probably "official" ways of verifying it, using a network sniffer is a poor man's version. I ran Wireshark and sniffed network traffic and compared a non-SSL connection and an SSL connection and looked at the raw data. I could easily see raw text data in the non-SSL version while the SSL "looked" encrypted. That, of course, means absolutely nothing. But it does show that "something" is happening to the data. In other words, if you think you are using SSL but can recognize the raw text in a network sniff, then something is not working as you expected. The converse is not true, though. Just because you can't read it, it does not mean it is encrypted.