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Amanda Rousseau
2017-11-21 13:19:52 -08:00
parent d153cae91b
commit 466fbec4e6
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flareon4/challenge3.md
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@@ -27,6 +27,15 @@ The hint here is the value tested against 0xFB5E. There is a function that proce
The first loop preps the answer array.
![alt text](https://securedorg.github.io/flareon4/images/ch3_loop.png "first loop")
In python it looks like this:
```
answer = stored_bytes[:]
for i in range(size):
x = char ^ answer[i]
x = (x + 0x22) & 0xff
answer[i] = x
```
## Main algorithm ##
The 4011E6 will then take the answer array in reverse and do some bit shifting while chaining addition based on 2 bytes because of the usage of ax and cx. This value will eventually equal to 0xFB5E.
![alt text](https://securedorg.github.io/flareon4/images/ch3_aglo.png "algorithm")