60 lines
5.2 KiB
Markdown
60 lines
5.2 KiB
Markdown
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# Retro
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## Writeup
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For this challenge, some information was broadcasted over the names of several wifi networks:
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`ffffffffffffc06101df6b7d0`
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`d16f45d14345d15545df757d1`
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`c05501ffe1ffce2bcfcba2252`
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`f008ebc3e683dc297bffd0df3`
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`c0496bdf5847d16511d161ff4`
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`d16551df4e87c05b1bffffff5`
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If you analyse the names, you can see that they are hexadecimal numbers, 25 characters long. Each name represents some binary information. You might also note that every name ends in a number ranging from 0 to 5: this number signifies the order in which you should look at this data.
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Thus, if you take the first 24 characters of every name in order and convert the full hexadimal string to binary you get the following data:
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`111111111111111111111111111111111111111111111111110000000110000100000001110111110110101101111101110100010110111101000101110100010100001101000101110100010101010101000101110111110111010101111101110000000101010100000001111111111110000111111111110011100010101111001111110010111010001000100101111100000000100011101011110000111110011010000011110111000010100101111011111111111101000011011111110000000100100101101011110111110101100001000111110100010110010100010001110100010110000111111111110100010110010101010001110111110100111010000111110000000101101100011011111111111111111111111111`
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The bytestream represents a monochrome image, if you replace every 0 with a ██ and every 1 with a ░░, you get the following (24x24) QR-code:
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<pre>
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░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░
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░░░░██████████████░░░░████████░░██████████████░░
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░░░░██░░░░░░░░░░██░░░░██░░██░░░░██░░░░░░░░░░██░░
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░░░░██░░██████░░██░░░░██░░░░░░░░██░░██████░░██░░
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░░░░██░░██████░░██░░████████░░░░██░░██████░░██░░
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░░░░██░░██████░░██░░██░░██░░██░░██░░██████░░██░░
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░░░░██████████████░░██░░██░░██░░██████████████░░
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░░░░██████████████░░████░░████░░██░░░░██░░██░░░░
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░░░░██░░░░░░░░░░██░░████░░░░░░██░░████████░░░░░░
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░░░░██████████████░░██░░░░██░░░░██████░░░░██░░░░
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░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░
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</pre>
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Scanning it with a QR-code reader will give you the flag, `IG{IkHouVanQR}`.
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## Challenge name
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The 'retro' name is a pointer to the homebrew programming community, where hackers actively create new games and programs for many retro gaming consoles.
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Representing images (commonly known as sprites) as hexadecimal numbers is a very common practice.
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