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Secure Mobile Browsing

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I’ve written, and rewritten this post about three times already, and I’m tired of thinking about it. I’m just going to write out whatever comes to mind on the subject and just post it as is.

This started as a conversation with wife about the safety of mobile banking. We were driving away from our credit union and I wanted to check to see if a transaction had posted yet, so I pulled out my smart phone and browsed to the credit union’s site and checked. She told me that she has reservations about browsing sensitive (banking, email, etc.) on a smart phone.

With this post I intend to explain what happens when you browse the mobile web and hopefully put to rest some fears.

Websites can be connected to in two different ways: unencrypted (HTTP) or encrypted (HTTPS). Most sites will use a hybrid approach and use HTTPS for the login or checkout page, and then HTTP for the rest of the site. Banks however, should use HTTPS 100% of the time. I blogged a while back about HTTPS, so I’m just going to paste what I wrote then here:

[With HTTPS] the goal is to establish a unique encryption session between your computer and the server, so that eavesdroppers aren’t able to steal your valuable information as it gets sent along the line. This is accomplished by using the Secure Socket Layer (SSL) protocol. SSL uses public-key cryptography to securely establish a session (symmetric) key that is used to protect the subsequent data. This is how it works:

Client (you and your browser) connects to a server over https:// (port 443)

Server sends you it’s public certificate – This certificate contains the server’s public key .

Client generates a random number, encrypts it with the server’s certificate and sends it – This number is the premaster key

Server takes the premaster key along with some other random numbers that were exchanged and generates the session key

Now that you and the server have agreed on the same key all the data sent from this point forward will be encrypted.

So we can now settle on the fact that if the site you are browsing to is using HTTPS, then no one can eavesdrop and steal any of your info. This is true whether you are browsing from your home computer, work computer, mobile phone connected to 3G, or mobile phone connected to an open Wi-Fi network.

So, why do some people say it is unsafe? There is an added risk of phishing attacks when you are browsing on a network you don’t trust (unsecured open Wi-Fi). Since all the traffic from your phone to the website will have to travel through this router that you don’t trust, the attacker could send you to a page that looks just like your bank’s page, at which you will log in, get some sort of error, and then be redirected to the real page. You will probably think that you typed your password wrong, try again, get through, and never think twice about it again.

So that is the only reason why you shouldn’t do any sensitive browsing on an open Wi-Fi network. All other networks are safe, provided the site uses HTTPS. If it doesn’t, it doesn’t matter if you trust the network or not, everyone can see everything you do.

Would love some questions if anything is unclear and I will do a follow-up.

Written by Nathan

May 11, 2011 at 10:50 am

Posted in Security

Tagged with ,