Test code hack

This paper mainly provides the identification idea of the current extreme inspection.

The verification code is mainly divided into 4 steps.

1/Restore the validated picture. Through the analysis of CSS, found to be a fixed position, a picture into a number of parts, in accordance with the specified order of rearrangement, so difficult.

2/Restore the good picture, find out the difference of 2 pictures, namely BG (verify diagram) and FULLBG (full image). This is not a very difficult task, by pixel or by block to scan. Set a threshold that, when the difference between 2 picture blocks or pixels is higher than the threshold, scan the right side for a few pixels, for example 10, if 7 of the 10 pixels are above this pixel. The x-coordinate of the image in which this pixel is located is the coordinate point we want. In this way, the probability of identifying coordinates is almost 80%, so the difficulty is not very easy.

3/Generate trajectory. This is the entire identification, the most difficult, but also the majority of the cracker stuck place. Moving tracks from x=0 to the coordinates of the second X, generates a two-dimensional array. Start by holding down the slider, and each move will get an array

{x-coordinate, y-coordinate, time-consuming (milliseconds) from start to present}

Moving all the way to the hole in the picture generates n such {{x coordinates, y-coordinates, time-consuming (milliseconds)},{x coordinates, y-coordinates, time-consuming (milliseconds)},{x coordinates, y-coordinates from start to now, and time-to-current (milliseconds)} ....} Trajectory.

The algorithm generated by this trajectory requires constant attempts. Until the server is recognized by the extreme. Otherwise the "Monster eats the Picture".

4/After you get this array of traces, you need to encrypt the array. Get a value. This algorithm and the subsequent userresponse are not difficult. Passtime the number of milliseconds that have elapsed between the start of the slider and the release slider. That is, the 3rd value of the last array of the trace two-dimensional array. imgload picture loading time. A suitable value at random.

The overall 4 steps. only provide ideas.

Original non-reproduced articles. Reprint please bring the following information.

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Test code hack