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Visual cryptography using pixels partition
1. Visual Cryptography using Pixels Partition
Yi-Hsin Ma 2018/01/09
• Idea: To encrypt a color image by taking a random N-partition of
each pixel, for R,G,B respectively.
• After the partition, there will be N images. My goal is to make
each picture unrecognized. Only with all picture and combine
them together can we recognize it.
MR_Trump.jpg
First Try
• n is the scale of a pixel, I choose two numbers a & b between 0 to
n using uniform distribution. Then we can split the whole picture
into three parts.
• The result is not good enough. (Mr. Trump can be recognized still.)
2. Problem
• Why can we still recognize Mr. Trump? Below are some problems I
had faced and waiting to be solved.
• The pixel which is nearly black not changing so much. Hence the
silhouette can still be seen.
• Pixels which are adjacent and nearly have the same color would
have same color after the partition , which make people easily to
recognize a “block”.
An Alternative Method
• Multiply each pixel with 19 which is coprime with 255, then mod
255.
• Take that number with partition.
3. After sum up all pictures, I transfer is by multiply 94 ( which is 19^-1 in
Z255 ) mod 255
If losing some pictures and transform back …
