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th3jackers 2015 CTF crypto200 writeup

24 January 2015 No Comment

The last word (crypto200)

Description: Decrypt this

And attachment is supplied: challenge.txt

It looks hex’ish? so i try hex decoding with no luck.

Then i noticed it had too many zeros? so i tried to change every character that’s not 0 to 1 to try for binary.

So as usual i run to python: cry200.py

0110001001110101011010010010000001111000011001000110100101110100001000000
1101101011010110010000001101100011100000111001000100000011100100111001101
1001010110110100100000011000100110101000100000011101110111011001110001011
0011101110011011010100010110101100001011101100010110101110000011011000110
0001011101110110111000100000011000100110101000100000010011110110000101110
0110111011001110000011101110111001101110011011001100010000001100001011101
1101110100011000010111011001111000011101110010000001001001010011100100010
10101001101010011

That decodes to:

bui xdit mk lpr rsem bj wvqgsj-av-plawn bj Oasvpwssf awtavxw INESS

And from the look of it it looks like some kind of substitution cipher:
I tried rot-n, with no luck.
Also i tried simple Caesar without luck.

Then i tried Vigenère cipher but i don’t have a key?!
I remembered the challenge name: “the last word”

Then i tried it with this website and i got:
the flag is the name of editor-in-chief of wikileaks

And the key would be:
flag{Julian Assange}

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