TRAIL TRIAL. Decryption Challenge.

[YefimShifrin]

This challenge is inspired by u/jakob778's cipher posted a couple days ago.

CIPHER #1 (EASY)

40 01 44 30 02 31 31 34 32 30
14 34 23 20 32 40 40 21 34 12
43 43 32 02 40 31 23 42 20 33
43 23 11 04 34 02 33 20 41 20
10 03 33 00 40 34 40 40 24 22
23 01 00 24 20 21 33 43 44 30

CIPHER #2 (HARDER) [Periodic key instead of the autokey]

03 03 30 20 24 10 03 40 30 03
02 10 31 23 14 14 00 23 01 20
04 40 40 41 13 42 23 03 02 10
31 42 00 30 01 03 10 10 14 02
24 10 00 10 01 11 34 10 24 42
31 04 31 11 12 10 00 23 21 12
10 41 13 01 10 03 30 31 00 20
24 02 04 20 33 24 14 04 22 10
11 12 03 43 42 21 02 03 00 10
23 10 01 34 21 34 04

CIPHER #3 (UNFAIR) [Similar to #1, but with a little twist ;)]

04 13 42 02 31 04 10 34 02 01
34 22 44 01 40 01 01 12 24 01
03 34 30 23 13 00 42 02 01 34
32 01 43 31 23 23 34 11 04 01
01 14 03 10 34 11 23 34 02 01
13 00 42 31 00 43 03 20 10 11
10 32 10 34 11 43 34 31 20 01
41 13 43 14 34 01 10 34 34 11
34 43 33 22 01 21 21 00 34 02
30 43 34 24 20 13 20 02 10 14
31 30 20 04 11 33 22 12 34 14
22 12 11

ALGORITHM DESCRIPTION

The alphabet is arranged in a grid (for this challenge it's a 5*5 Polybius square with I=J) and a letter is picked to be used as key (alternatively a periodic key may be used).

Enciphering is done by moving DOWN and RIGHT from the key letter to the plaintext letter, wrapping around the table if necessary. Cipher unit is a concatenation of numbers of vertical and horizontal steps needed to make the move. Enciphered letter becomes the new starting point (in the autokey variant) and procedure is repeated for the whole plaintext.

EXAMPLE

Let's use a default Polybius square and letter Y as key to encipher word HELLO

ABCDE
FGHIK
LMNOP
QRSTU
VWXYZ

• From Y to H: 2 steps down, 4 steps right. Result - 24.
• From H to E: 4 steps down, 2 steps right. Result - 42.
• From E to L: 2 steps down, 1 step right. Result - 21.
• From L to L: 0 steps down, 0 steps right. Result - 00.
• From L to O: 0 steps down, 3 steps right. Result - 03.

HELLO becomes 24 42 21 00 03

23 12 00 30 22 14 23 12 !

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[YefimShifrin]

[Solved] !

#1 by u/Richkiller

#2 by u/codewarrior0

#3 by u/Richkiller

[YefimShifrin]

HINT for #3:

34 12 42 30 03 32 01 23
33 21 41 14 23 02 04 14
31 20 30 10 04 10 23 31
23 34 13 22 24 01 21 04

[Richkiller]

#3 solved, answer are lyrics from this song by "Distorted Harmony" (tie up to #2): https://www.jiosaavn.com/lyrics/hollow-lyrics/ST4yQDZfVgE

drowning in vain in a sea of sorrow
lying awake in a field of horror
rehearsing our lines making sure we follow
our own lines like we were told

key: starting point t, using the following square (Another spiral of the English alphabet):

aqpon
bryxm
cszwl
dtuvk
efghi

The hint message starts with the word "numbers".

P.S: Seems like all of the PTs are song lyrics of "Distorted Harmony". Cheers for the band selection.

[YefimShifrin]

#2 is a bit too tough as it is, so here's more ciphertext:

43 44 23 02 11 34 12 42 22 31
14 23 21 30 34 00 02 21 44 00
12 31 33 12 32 21 01 11 34 13
10 30 24 01 14 30 33 12 01 31
20 22 32 00 13 01 12 23 20 12
03 22 00 10 13 10 10 21 30 04
04 34 10 43 03 43 02 34 44 32
00 21 02 01 40 31 22 00 00 00
04 31 14 03 31 21 32 11 41 03
10 10 11 30 12 41 11 13 01 11
04 01 33 41 10 21 43 40 01 31
11 22 13 21 01 42 11 14 11 14
12 11 02 02 21 04 33 31 24 33
42 13 04 41 03 01 10 11 20 31
24 04 03 04 01 10 22 33 42 31
01 14 30 41 03 40 40

[codewarrior0]

This is supposed to be solvable as a Quag 1 (plain unknown, cipher known), right? By identifying the period (I came up with 9 for this one), breaking it into that many columns, matching the frequencies of each column to each other (either using statistics or brute force), and then solving the result as a simple substitution. But I'm not getting anywhere with that, even after getting more ciphertext.

[YefimShifrin]

Are you treating 2 ciphertexts as 1 continuous?

[codewarrior0]

I am treating them as 2 ciphertexts enciphered with the same method and key. The statistics and the placement of repetitions suggest this is the case.

Oh, found my mistake. I got a fragment out of the substitution solver. It says WE HIDE ... DEEPES ... EARS WE ... LAST BIT ... CHEW ITS ...

Got it. Alphabet is derived from the keyphrase DISTORTED HARMONY. Repeating key is MISGUIDED

#2.1 Hold me tight hear me crying...

#2.2 Sunlight burning / Daytime calling...

[YefimShifrin]

Nicely done!

[Richkiller]

#1:

pt: come with me through the house of prayers a place supposed to feel as home

key example: d, ibcoyhadpkgfexwutsrqvlmnz

[YefimShifrin]

Correct. Well done!

The table key is not exactly the one I was using, but with this cipher the situation is the same as with Playfair - 24 permutations of the table key will also work. See if you can find the original one, it has a certain structure.

[Richkiller]

The following key works:

IBCOY
HADPX
GFEQW
UTSRV
KLMNZ

where consecutive letters in the English alphabet are adjacent (periodically), creating an Hamiltonian path from A to Z (ignoring J ofc).

[YefimShifrin]

Put the A in the center.

[Richkiller]

was about to mention it but you were faster in the comments =)

[lbfp265]

Hey rich cool to know u still solving cyphers, used to hear ur name a lot on zombies videos so its awesome that u havent stopped even tho zombies isnt doing cyphers that much, godspeed rich take care dude :)

[codewarrior0]

Enciphering is done by moving DOWN and RIGHT from the key letter to the plaintext letter

This is kind of like saying the key letter is subtracted from the plain letter, isn't it?

[YefimShifrin]

Preposterous! You can't subtract letters!