how to make an unbreakable cipher

a while back i came up with a silly thing that now goes in a lot of my online presences

it's this: b618ac8ac69b6ac7bae267acb1a81e

a few people have actively not been able to figure out what it means at all so i'm going to actually spoil it (but try it if you want before continuing!)

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so i realize there really isn't a lot to work with here but here's some basic analysis

• it's hexadecimal, representing 30 bytes
• the only repeating byte is ac at position 2 and 11

no hash or checksum or anything similar that i know of is 30 bytes. none of this is really printable either

00000000: b618 ac8a c69b 6ac7 bae2 67ac b1a8 1e    ......j...g....

so here's how you figure it out. the length is a multiple of 3, and the repeated byte also appears at 2 mod 3 both times

there's a basic encoding mechanism that converts every sequence of 3 bytes into a sequence of 4 bytes. it's usually used to encode stuff in the forward direction. like this: aHVudGVyMgo=
it's fairly recognizable that way due to the character set and usually having trailing = chars. so what i did was i reversed it. instead of base64 encoding, i base64 decoded a message and that's what that code actually is. that's why it has the few clues relating to 3, because that's the coding unit for base64

anyway, it's boring, but here's a solution in bash

$ echo b618ac8ac69b6ac7bae267acb1a81e | xxd -r -p | base64
thisisabase64message

it's a base64 message. maybe not the coding direction you'd expect though. i'm honestly surprised no one ever got this, but i guess it is fairly sneaky :P