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User-Friendly Multi-Factor Authentication with GrIDsure

I have been tasked with rolling out a trial multi-factor authentication system that must be user-friendly, secure, low-cost and have zero impact on the existing network and users who won't be on the trial. That should be simple!

A trawl round the InfoSecurity Europe show always helps, as you can get the latest state of play from all the major vendors. This year there were the obvious keyring tokens, SmartCards, USB tokens, SMS solutions and some innovative software solutions, including GrIDsure. Before making any decisions about the solution to go for, several things need to be decided, among which are: how much security is required? What is considered user-friendly to a normal, non-technical user? What metrics should we use for authentication?

To answer these we need to look at what authentication is first: Authentication is the binding of an identity to a subject. The subjects we're talking about in this case are users and we're trying to bind their digital identity, i.e. user ID, to them as an individual. There are four metrics we can use to query identity, namely:
  • What they know - e.g. password, PIN, secret/personal information, etc.

  • What they have - e.g. token, SmartCard, phone, etc.

  • What they are - i.e. biometrics

  • Where they are (in space and time) - e.g. particular terminal, logon hours, etc.
The most common form of authentication is username/password, but this is outdated, insecure and, usually, fairly easily cracked (but that's another post). The problem is that each of these on their own is not very secure (yes, even biometrics are not that secure used on their own in a large environment). If we use a combination then we can obtain secure, strong authentication (by strong authentication we mean that we are sure about the identity of this subject as it would be very hard to have all the required metrics otherwise). RSA-type tokens and SmartCards combined with a PIN or password are easy and obvious choices to deploy, but they have issues. They are expensive to deploy, as you have hardware costs as well as the authentication servers. From a user perspective, they have to carry round something else with them. That's not usually too much of a problem, as these are small devices or credit-cards, but you have to have a reader for a SmartCard. Lost or damaged hardware (or tokens that have run out of battery) have to be replaced at a cost.
OK, so we could use SMS, whereby a text message is received by the user containing a one-time password. This is often done by sending one on-demand to the user when they start the login process. What if the network is down? What if there are delays on the network? Well, we can deliver the password up front, i.e. when they log off we can send them the password to use next time they want to login, but then it's hanging around on their phone, which they might lose. So what's the solution? Well, I saw two products that are noteworthy: Swivel Authentication Solutions and GrIDsure.
Swivel's solution relies on either secure SMS or a Turing image (one that is human-readable but not computer-readable). The Turing image will show two rows of numbers, the first is 0 to 9 and the second is the numbers in a random order. The idea is that you have a PIN number that you remember and you read off a one-time PIN from the image. So, if your PIN was 2468 then your one-time PIN for this login attempt would be 7193 from the image below. If someone uses a keylogger, then it will be defeated by this, as that PIN won't be valid next time and it hasn't revealed the base PIN number that you remember. However, if someone uses keylogger and screen capture malware, then it could be read off and deduced - possibly a big ask. However, you could shoulder-surf the pattern as well. That being said, this is very easy to deploy and relatively cheap. Users find it fairly simple to use as well, and it has to be better than a static PIN.

However, there is another solution - GrIDsure. With GrIDsure, you choose a pattern on a grid to remember. The grid size and pattern length is configurable, but the standard is to have a four square pattern on a 5x5 grid. You remember this pattern and then, when you attempt to login, you will be presented with a 'random' grid of numbers. You then read off the numbers in your pattern. For example, if your pattern is the tick that GrIDsure use as their demo and you are presented with the grid shown below, then your one-time PIN number would be 0649. This would change every time you log in. This now defeats keyloggers and shoulder surfing, as each digit will appear more than once. So, even if you see or log the grid and someone typing 0649, there are 81 patterns that would result in this PIN on the grid shown below. It is important to remember that you do not type or click the grid. The grid is just an image; you type the PIN in on a standard keypad.

This can be made more secure by deploying the grid on your mobile phone as a Java applet rather than in the web page, thus defeating screen capture. The grids, in this instance, are seeded from the phone's unique ID, so someone else has to have your actual phone, not just the applet running on their phone. This is true multi-factor authentication, as it requires the physical phone and a pattern that the user knows, without both you cannot authenticate. Also, this is a cheap to deploy solution as most users will already have a mobile phone, and those that don't can drop back onto the single-factor one-time passcode by displaying the grid in a browser. Users also find this very simple to use, as many people already remember their PIN numbers as a pattern anyway. This also 'plays nicely' with other authentication, i.e. you can still use username and password for some users and GrIDsure for others as the desktop client accepts both. Similarly, the web portal is able to interface with virtually any web-based application as a single-sign-on solution. Of course existing users can still hit the services direct and use traditional authentication until this has been deployed to all.


  1. hi. have you looked at fireid? (

  2. I hadn't seen that, thanks. It looks interesting. A PIN for the application should be on by default rather than an option though. This is basically a Hash-chain application, but nicely done.

  3. Luke, ur welcome to investigate FireID in more depth by dropping me an email from the website :)

  4. Luke, check out for both password and PIN aplications. Would love to be in your bake-off!

  5. Thanks PGS. I need to have more of a look around at the various new options. Obviously, your solution has many more permutations to convert knowledge into a one-time passcode. This is a single-factor, but complex one-time passcode solution.

    I have a reasonably large set of relatively tame users that I may run a trial of several products with and publish my findings in another blog post.


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