Quote from: MrFreeDragon on Today at 01:44:26 PM

Just to show again that I did not invent a monster but used a prototype. Of course it is not a classic space invader, but it exists and could be found in different stock images by key words "pixel monsters":

Changes: one more column to the center, one more pixel for every leg, eyes aligned with the mouth

It was a nice puzzle and fun to try. I think the number of possibilities wasa tad high to manually find it though. As an estimate: say there are 100 more or less obvious pictures that can easily be found on the internet, each with a several details that can be changed giving at least thousands of combinations per image.

Quote from: akkort on Today at 02:13:57 PM

Exact. I created Giant Step hashtable for 2^29 symmetrical combinations. Then, check Baby Step for second half of picture, also 2^29 symmetrical combinations.
Border+one half = Giant Step
second half - public key = Baby step

Memory spent for giant step is about 6Gb, can be safe reduced to 3-4Gb. 20 minutes to build hashtable.
baby step takes about 2 minutes to find key.
BSGS can be used for keys up to 70-75 bits.

I'm impressed! Congratulations!