Wednesday, October 7, 2009

CAPTCHA vs. Strong Authentication (with OAAM)

A colleague was asked by a customer for a comparison between using a CAPTCHA solution and Oracle Adaptive Access Manager (OAAM). As people try to understand the role of CAPTCHA and different “advanced” authentication solutions in general, this type of question is actually pretty common.

The most common CAPTCHA solutions involve a user picking a series of alphanumeric characters (often distorted or partially obfuscated) out of a generated image and entering the characters along with the rest of the input.

CAPTCHA injects this specific type of challenge-response flow into an authentication (or other web input) to ensure that the input is really coming from a human and not a computer. It is often used with authentication, self-registration, and other application specific interactions like concert ticket buying systems to prevent various denial of service attacks and other mass input abuses of the system.

While CAPTCHA (arguably) does a good job at making sure that a user really is human, that is all that it does. It does nothing to make an actual user authentic stronger. It does nothing to prevent phishing, nothing to detect or prevent fraud, nothing to mitigate stolen passwords. The credentials being supplied in a username and password form with CAPTCHA is still just a username and password.

On the other hand, strong authentication is about adding additional “stronger” credentials into the authentication to go along with a username and password. Usually this means incorporating something a user has like an ATM card, hardware authentication token, or software token or alternatively something a user knows like a series of personal questions that other people aren’t likely to know.

Along with strong authentication often come secure input technologies like personalized pictures and phrases, keypads, and sliders that are utilized to prevent phishing and stolen passwords in general.

OAAM is an exceptionally powerful yet easy to use and deploy strong authentication and fraud prevention solution. You can read more about its capabilities here and by reading the white paper found here. On a personal note, I think OAAM is a very strong product and a leader in the space.

While there is overlap between OAAM (or strong auth in general) and CAPTCHA technologies in that a strong auth solution can help ensure that an application is interacting with a human, there is still a conceivable need for both.

Strong authentication is for well… authentication and requires that a user exist and that additional authentication factors be provisioned prior to the authentication. This makes it inappropriate for registration and other interactions where the user may be anonymous. On the other hand CAPTCHA can be used without knowing specifically who a user is.

It may also be appropriate to use CAPTCHA in an interaction that occurs at some point after (strong) authentication to ensure that a human is still in control of the client system.

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