Question

Few examples of CAPTCHA would be Gimpy and Bongo.

Please explain how both work in details.

Also, do describe the pros and cons of using both of them in details.

From there, conclude each of them work best under what circumstances.

P.S. Please don't copy and paste directly from online sources.

Answer 1

Gimpy.gimpy works as follows:

it picks seven words out of a dictionary, and renders adistorted image containing the words (as shown in the figure below). gimpy then presents atest to its user, which consists of the distorted image and the directions:

Answer 2

Proving that you're a human to a computer is another matter. It requires a test (or a set of
tests) that computers can grade, humans can pass, but paradoxically, computers can't pass. In our
lingo, it requires a captcha.

Gimpy: Gimpy works as follows: it picks seven words out of a dictionary, and renders a
distorted image containing the words (as shown in the gure below). gimpy then presents a
test to its user, which consists of the distorted image and the directions: \type three words
appearing in the image". Given the types of deformations that gimpy uses, most humans can
read three words from the distorted image, while current computer programs can't.

Bongo. Another example of a captcha is the program we call bongo.2 bongo asks the
user to solve a visual pattern recognition problem. In particular, it displays two series of
blocks, the Left and the Right. The blocks in the Left series di er from those in the
Right, and the user must nd the characteristic that sets them apart. A possible Left and
Right series are shown below:

(These two series are di erent because everything in the Left is drawn with thick lines, while
everything in the Right is drawn with thin lines.) After seeing the two series of blocks, the
user is presented with a single block and is asked to determine whether this block belongs to
the Right series or to the Left. The user passes the test if he or she correctly determines
the side to which the block belongs to.

10

Gimpy is very reliable and secure CAPTCHA. In this CAPTCHA ten random words from the dictionary are fetched, display these words in overlap and distorted manner. Then Gimpy ask the user to enter at least three words from those ten words. The human user can do so but computer bots can