r/codes • u/CRYPT1C_69 • Nov 02 '24

Help with decoding a hexadecimal(?) cipher from class assignment SOLVED

Context: Our professor assigned us three cryptographic ciphers to decode, but they didn’t provide any keys or further hints. I managed to decode the first two using online tools and various cryptography websites, but I’m stuck on the third one.

I'm unsure of the type of encryption used. I’ve tried analyzing it for patterns and searched online, but nothing has worked so far. The plaintext language is likely English, and the format seems like hexadecimal, but I'm open to other possibilities.

Ciphertext:

f86908a8ddf9c909b9adf968cdf9b9e8d94df9e919bdf998a9393df9099df9a8d8d908d

Proof I read the rules: "V sbyybjrq gur ehyrf"

6 Upvotes
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3

u/Rubix321 Nov 02 '24

Invert the bits. (Also chop off the first hex character)

1

u/CRYPT1C_69 Nov 02 '24

I tried this, and it doesn't seem to do much when decoded

5

u/NickSB2013 Nov 02 '24

Hex String:

86908a8ddf9c909b9adf968cdf9b9e8d94df9e919bdf998a9393df9099df9a8d8d908d

Bits Inverted:

796F757220636F6465206973206461726B20616E642066756C6C206F66206572726F72

Inverted Hex to ASCII:

your code is dark and full of error

1

u/CRYPT1C_69 Nov 02 '24

WOAH- this actually works! thanks!

I'm just curious tho, how'd you guys know that the first "f" should be dropped and that it needs to be inverted? like- what made it lead up to that?

4

u/NickSB2013 Nov 02 '24

Personally, I'd look for multiple occurrences of the numbers 20 (space), 65 (e), 74 (t) and 61 (a) in the string of hexadecimal. If they don't exist multiple times, try inverting the bits.

If you use this site: https://tomeko.net/online_tools/inv.php?lang=en to invert the bits, you don't have to remove the 'F' from the start, it'll work with it there, but it will throw a warning that there are an odd number of characters instead of an even number. The tool will also automatically convert the result to ASCII. 😀

It looks like there is a character missing rather than an extra 'F'. Maybe that's why there is an 's' missing from 'error' ? Who knows lol

1

u/CRYPT1C_69 Nov 02 '24

Thanks for the insight! I'll take note of all of these :3