CTF #nullcon 2012: Programación 4

• January 30, 2012
• tuxotron
• Programación, Hacking, Cyberlab

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En este reto nos encontramos con un problema de sustitución.

Estos son los datos que se nos dan:

Ciphertext:
06 15 21 20 05 05 14 00 14 09 14 05 00 06 15 21 20 05 05 14 00 06 09 22 05 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 19 09 24 00 14 09 14 05 00 20 23 05 14 20 25 20 23 15 00 06 09 22 05 00 26 05 18 15 00 19 09 24 00 06 09 06 20 05 05 14 00 20 23 05 14 20 25 15 14 05 00 05 09 07 20 05 05 14 00 26 05 18 15 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 20 23 05 14 20 25 00 20 23 05 14 20 25 06 09 22 05 00 06 09 06 20 05 05 14 00 06 15 21 20 05 05 14 00 06 09 22 05 00 26 05 18 15 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 22 05 00 20 23 05 12 22 05 00 20 23 05 14 20 25 20 23 15 00 06 09 22 05 00 26 05 18 15 00 19 09 24 00 14 09 14 05 00 19 09 24 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 20 23 05 14 20 25 00 20 23 05 14 20 25 06 09 22 05 00 06 09 06 20 05 05 14 00 06 15 21 20 05 05 14 00 06 09 22 05 00 26 05 18 15 00 06 15 21 20 05 05 14 00 14 09 14 05 00 06 15 21 20 05 05 14 00 06 09 22 05 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 22 05 00 20 23 05 12 22 05 00 20 23 05 14 20 25 20 23 15 00 06 09 22 05 00 26 05 18 15 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 20 23 05 14 20 25 00 20 23 05 14 20 25 06 09 22 05 00 19 09 24 00 14 09 14 05 00 20 23 05 14 20 25 20 23 15 00 06 09 22 05 00 26 05 18 15 00 20 23 05 14 20 25 19 09 24 00 06 09 22 05 00 05 09 07 20 05 05 14 00 06 09 06 20 05 05 14 00 26 05 18 15 00 19 09 24 00 14 09 14 05 00 20 23 05 14 20 25 20 23 15 00 06 09 22 05 00 26 05 18 15 00 06 15 21 20 05 05 14 00 14 09 14 05 00 06 15 21 20 05 05 14 00 06 09 22 05 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 20 23 05 14 20 25 00 05 09 07 08 20 00 05 09 07 20 05 05 14 00 06 09 22 05 00 06 09 22 05 00 26 05 18 15 00 06 09 22 05 00 14 09 14 05 00 19 05 22 05 14 00 05 09 07 08 20 00 20 23 05 14 20 25 00 26 05 18 15 00 19 09 24 00 14 09 14 05 00 20 23 05 14 20 25 20 23 15 00 06 09 22 05 00 26 05 18 15 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 20 23 05 14 20 25 00 20 23 05 14 20 25 06 09 22 05 00 20 23 05 14 20 25 00 05 09 07 08 20 00 05 09 07 20 05 05 14 00 06 09 22 05 00 06 09 22 05 00 26 05 18 15 00 20 23 05 14 20 25 19 09 24 00 06 09 22 05 00 05 09 07 20 05 05 14 00 06 09 06 20 05 05 14 00 26 05 18 15 00 19 09 24 00 14 09 14 05 00 19 09 24 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 06 20 05 05 14 00 26 05 18 15 00 14 09 14 05 20 05 05 14 00 14 09 14 05 00 20 23 05 14 20 25 06 15 21 18 00 26 05 18 15 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 20 23 05 14 20 25 00 20 23 05 14 20 25 06 09 22 05 00 06 09 06 20 05 05 14 00 06 15 21 20 05 05 14 00 06 09 22 05 00 26 05 18 15 00 06 15 21 20 05 05 14 00 14 09 14 05 00 06 15 21 20 05 05 14 00 06 09 22 05 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 20 23 05 14 20 25 00 05 09 07 08 20 00 05 09 07 20 05 05 14 00 06 09 22 05 00 06 09 22 05 00 26 05 18 15 00 06 09 06 20 05 05 14 00 06 15 21 20 05 05 14 00 06 09 22 05 00 26 05 18 15 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 20 23 05 14 20 25 00 20 23 05 14 20 25 06 09 22 05 00 26 05 18 15 00 19 09 24 00 14 09 14 05 00 19 09 24 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 06 09 22 05 00 14 09 14 05 00 19 05 22 05 14 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 20 23 05 14 20 25 00 20 23 05 14 20 25 06 09 22 05 00 19 09 24 00 14 09 14 05 00 20 23 05 14 20 25 20 23 15 00 06 09 22 05 00 26 05 18 15 00 20 23 05 14 20 25 19 09 24 00 06 09 22 05 00 05 09 07 20 05 05 14 00 06 09 06 20 05 05 14 00 26 05 18 15 00 06 09 22 05 00 14 09 14 05 00 19 05 22 05 14 00 05 09 07 08 20 00 20 23 05 14 20 25 00 26 05 18 15 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 20 23 05 14 20 25 00 20 23 05 14 20 25 06 09 22 05 00 19 09 24 00 14 09 14 05 00 20 23 05 14 20 25 20 23 15 00 06 09 22 05 00 26 05 18 15 00 14 09 14 05 20 05 05 14 00 14 09 14 05 00 20 23 05 14 20 25 06 15 21 18 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 19 09 24 00 14 09 14 05 00 20 23 05 14 20 25 20 23 15 00 06 09 22 05 00 26 05 18 15 00 06 09 22 05 00 14 09 14 05 00 19 05 22 05 14 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 20 23 05 14 20 25 00 20 23 05 14 20 25 06 09 22 05 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 06 20 05 05 14 00 26 05 18 15 00 19 09 24 00 14 09 14 05 00 20 23 05 14 20 25 20 23 15 00 06 09 22 05 00 26 05 18 15 00 06 09 22 05 00 14 09 14 05 00 19 05 22 05 14 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 06 20 05 05 14 00 26 05 18 15 00 19 09 24 00 14 09 14 05 00 19 09 24 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 06 15 21 20 05 05 14 00 14 09 14 05 00 06 15 21 20 05 05 14 00 06 09 22 05 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 06 15 21 20 05 05 14 00 14 09 14 05 00 06 15 21 20 05 05 14 00 06 09 22 05 00 26 05 18 15 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 20 23 05 14 20 25 00 20 23 05 14 20 25 06 09 22 05 00 26 05 18 15 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 20 23 05 14 20 25 00 20 23 05 14 20 25 06 09 22 05 00 19 09 24 00 14 09 14 05 00 20 23 05 14 20 25 20 23 15 00 06 09 22 05 00 26 05 18 15 00 20 23 05 14 20 25 19 09 24 00 06 09 22 05 00 05 09 07 20 05 05 14 00 06 09 06 20 05 05 14 00 26 05 18 15 00 06 09 06 20 05 05 14 00 06 15 21 20 05 05 14 00 06 09 22 05 00 26 05 18 15 00 19 09 24 00 06 09 06 20 05 05 14 00 20 23 05 14 20 25 15 14 05 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 19 09 24 00 06 09 06 20 05 05 14 00 20 23 05 14 20 25 15 14 05 00 05 09 07 20 05 05 14 00 26 05 18 15 00 20 23 05 14 20 25 19 09 24 00 06 09 22 05 00 05 09 07 20 05 05 14 00 06 09 06 20 05 05 14 00 26 05 18 15 00 14 09 14 05 20 05 05 14 00 14 09 14 05 00 20 23 05 14 20 25 06 15 21 18 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 06 09 22 05 00 14 09 14 05 00 19 05 22 05 14 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 19 09 24 00 14 09 14 05 00 19 09 24 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 22 05 00 20 23 05 12 22 05 00 20 23 05 14 20 25 20 23 15 00 06 09 22 05 00 26 05 18 15 00 06 15 21 20 05 05 14 00 14 09 14 05 00 06 15 21 20 05 05 14 00 06 09 22 05 00 26 05 18 15 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 20 23 05 14 20 25 00 20 23 05 14 20 25 06 09 22 05 00 19 09 24 00 06 09 06 20 05 05 14 00 20 23 05 14 20 25 15 14 05 00 05 09 07 20 05 05 14 00 26 05 18 15 00 06 15 21 20 05 05 14 00 14 09 14 05 00 06 15 21 20 05 05 14 00 06 09 22 05 00 26 05 18 15 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 20 23 05 14 20 25 00 20 23 05 14 20 25 06 09 22 05 00 26 05 18 15 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 20 23 05 14 20 25 00 20 23 05 14 20 25 06 09 22 05 00 19 09 24 00 14 09 14 05 00 20 23 05 14 20 25 20 23 15 00 06 09 22 05 00 26 05 18 15 00 20 23 05 14 20 25 19 09 24 00 06 09 22 05 00 05 09 07 20 05 05 14 00 06 09 06 20 05 05 14 00 26 05 18 15 00 20 23 05 14 20 25 00 05 09 07 08 20 00 14 09 14 05 00 05 09 07 20 05 05 14 00 20 23 05 14 20 25 00 20 23 05 14 20 25 06 09 22 05 00 06 09 22 05 00 14 09 14 05 00 19 05 22 05 14 00 05 09 07 08 20 00 20 23 05 14 20 25 00 26 05 18 15 00 20 23 05 14 20 25 00 05 09 07 08 20 00 14 09 14 05 00 05 09 07 20 05 05 14 00 20 23 05 14 20 25 00 20 23 05 14 20 25 06 09 22 05 00 19 09 24 00 06 09 06 20 05 05 14 00 20 23 05 14 20 25 15 14 05 00 05 09 07 20 05 05 14 00 26 05 18 15 00 20 23 05 14 20 25 19 09 24 00 06 09 22 05 00 05 09 07 20 05 05 14 00 06 09 06 20 05 05 14 00 26 05 18 15 00 06 09 22 05 00 14 09 14 05 00 19 05 22 05 14 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 19 09 24 00 14 09 14 05 00 19 09 24 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 19 09 24 00 14 09 14 05 00 20 23 05 14 20 25 20 23 15 00 06 09 22 05 00 26 05 18 15 00 19 09 24 00 06 09 06 20 05 05 14 00 20 23 05 14 20 25 15 14 05 00 05 09 07 20 05 05 14 00 26 05 18 15 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 20 23 05 14 20 25 00 20 23 05 14 20 25 06 09 22 05 00 19 09 24 00 14 09 14 05 00 20 23 05 14 20 25 20 23 15 00 06 09 22 05 00 26 05 18 15 00 20 23 05 14 20 25 19 09 24 00 06 09 22 05 00 05 09 07 20 05 05 14 00 06 09 06 20 05 05 14 00 26 05 18 15 00 14 09 14 05 20 05 05 14 00 06 09 22 05 00 20 23 05 14 20 25 20 23 15 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 06 09 22 05 00 14 09 14 05 00 19 05 22 05 14 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 19 09 24 00 14 09 14 05 00 20 23 05 14 20 25 20 23 15 00 06 09 22 05 00 26 05 18 15 00 19 09 24 00 14 09 14 05 00 20 23 05 14 20 25 20 23 15 00 06 09 22 05 00 26 05 18 15 00 19 09 24 00 06 09 06 20 05 05 14 00 20 23 05 14 20 25 15 14 05 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14

How we Obfuscated:

Plain Text = nullcon
After charset Substitution = 14 21 12 12 03 15 14
Literal Substitution = fouteen twentyone twelve twelve three fifteen fouteen
After charset Substitution = 06 15 21 20 05 05 14 00 20 23 05 14 20 25 15 14 05 00 20 23 05 12 22 05 00 20 23 05 12 22 05 00 20 08 18 05 05 00 06 09 06 20 05 05 14 00 06 15 21 20 05 05 14

charset = 00 means " ",  01 = "a", 02="b".... 26="z", 30 = "0", 31="1" .... 39="9"

Reiterate till you find meaning text

Tenemos el texto a descifrar (primer bloque de datos), luego tenemos el método usado para cifrar dicho texto y por último tenemos la correspondencia de caractares. Y dice que iteremos hasta encontrar un texto con sentido.

Lo primero que hice fue crearme una cadena de caracteres, en la que de acuerdo con los datos dados, cada carácter esté en la posición que se corresponda.

subs_string = " abcdefghijklmnopqrstuvwxyz@@@0123456789"

Como vemos, el primer carácter (posición 0) es el espacio en blanco, luego desde la posición 1 a la 26 tenemos el alfabeto (inglés) y los números empezando en la posición 30 de la cadena. Las ‘@’ entre las letras y los números son mero relleno, esas posiciones (27, 28 y 29) nunca serán accedidas. Podríamos haber usado cualquier otro carácter.

Otra estructura de datos que uso es un map, para poder traducir de letras a números. Esto lo fui rellenando a mano a medida que iba ejecutando iteraciones, porque si te fijas hay varios números que están mal deletreados (suponiendo que esto es inglés).

El script con el que solucioné este reto es el siguiente:

#!/usr/bin/env ruby

ciphered_text = "06 15 21 20 05 05 14 00 14 09 14 05 00 06 15 21 20 05 05 14 00 06 09 22 05 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 19 09 24 00 14 09 14 05 00 20 23 05 14 20 25 20 23 15 00 06 09 22 05 00 26 05 18 15 00 19 09 24 00 06 09 06 20 05 05 14 00 20 23 05 14 20 25 15 14 05 00 05 09 07 20 05 05 14 00 26 05 18 15 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 20 23 05 14 20 25 00 20 23 05 14 20 25 06 09 22 05 00 06 09 06 20 05 05 14 00 06 15 21 20 05 05 14 00 06 09 22 05 00 26 05 18 15 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 22 05 00 20 23 05 12 22 05 00 20 23 05 14 20 25 20 23 15 00 06 09 22 05 00 26 05 18 15 00 19 09 24 00 14 09 14 05 00 19 09 24 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 20 23 05 14 20 25 00 20 23 05 14 20 25 06 09 22 05 00 06 09 06 20 05 05 14 00 06 15 21 20 05 05 14 00 06 09 22 05 00 26 05 18 15 00 06 15 21 20 05 05 14 00 14 09 14 05 00 06 15 21 20 05 05 14 00 06 09 22 05 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 22 05 00 20 23 05 12 22 05 00 20 23 05 14 20 25 20 23 15 00 06 09 22 05 00 26 05 18 15 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 20 23 05 14 20 25 00 20 23 05 14 20 25 06 09 22 05 00 19 09 24 00 14 09 14 05 00 20 23 05 14 20 25 20 23 15 00 06 09 22 05 00 26 05 18 15 00 20 23 05 14 20 25 19 09 24 00 06 09 22 05 00 05 09 07 20 05 05 14 00 06 09 06 20 05 05 14 00 26 05 18 15 00 19 09 24 00 14 09 14 05 00 20 23 05 14 20 25 20 23 15 00 06 09 22 05 00 26 05 18 15 00 06 15 21 20 05 05 14 00 14 09 14 05 00 06 15 21 20 05 05 14 00 06 09 22 05 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 20 23 05 14 20 25 00 05 09 07 08 20 00 05 09 07 20 05 05 14 00 06 09 22 05 00 06 09 22 05 00 26 05 18 15 00 06 09 22 05 00 14 09 14 05 00 19 05 22 05 14 00 05 09 07 08 20 00 20 23 05 14 20 25 00 26 05 18 15 00 19 09 24 00 14 09 14 05 00 20 23 05 14 20 25 20 23 15 00 06 09 22 05 00 26 05 18 15 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 20 23 05 14 20 25 00 20 23 05 14 20 25 06 09 22 05 00 20 23 05 14 20 25 00 05 09 07 08 20 00 05 09 07 20 05 05 14 00 06 09 22 05 00 06 09 22 05 00 26 05 18 15 00 20 23 05 14 20 25 19 09 24 00 06 09 22 05 00 05 09 07 20 05 05 14 00 06 09 06 20 05 05 14 00 26 05 18 15 00 19 09 24 00 14 09 14 05 00 19 09 24 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 06 20 05 05 14 00 26 05 18 15 00 14 09 14 05 20 05 05 14 00 14 09 14 05 00 20 23 05 14 20 25 06 15 21 18 00 26 05 18 15 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 20 23 05 14 20 25 00 20 23 05 14 20 25 06 09 22 05 00 06 09 06 20 05 05 14 00 06 15 21 20 05 05 14 00 06 09 22 05 00 26 05 18 15 00 06 15 21 20 05 05 14 00 14 09 14 05 00 06 15 21 20 05 05 14 00 06 09 22 05 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 20 23 05 14 20 25 00 05 09 07 08 20 00 05 09 07 20 05 05 14 00 06 09 22 05 00 06 09 22 05 00 26 05 18 15 00 06 09 06 20 05 05 14 00 06 15 21 20 05 05 14 00 06 09 22 05 00 26 05 18 15 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 20 23 05 14 20 25 00 20 23 05 14 20 25 06 09 22 05 00 26 05 18 15 00 19 09 24 00 14 09 14 05 00 19 09 24 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 06 09 22 05 00 14 09 14 05 00 19 05 22 05 14 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 20 23 05 14 20 25 00 20 23 05 14 20 25 06 09 22 05 00 19 09 24 00 14 09 14 05 00 20 23 05 14 20 25 20 23 15 00 06 09 22 05 00 26 05 18 15 00 20 23 05 14 20 25 19 09 24 00 06 09 22 05 00 05 09 07 20 05 05 14 00 06 09 06 20 05 05 14 00 26 05 18 15 00 06 09 22 05 00 14 09 14 05 00 19 05 22 05 14 00 05 09 07 08 20 00 20 23 05 14 20 25 00 26 05 18 15 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 20 23 05 14 20 25 00 20 23 05 14 20 25 06 09 22 05 00 19 09 24 00 14 09 14 05 00 20 23 05 14 20 25 20 23 15 00 06 09 22 05 00 26 05 18 15 00 14 09 14 05 20 05 05 14 00 14 09 14 05 00 20 23 05 14 20 25 06 15 21 18 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 19 09 24 00 14 09 14 05 00 20 23 05 14 20 25 20 23 15 00 06 09 22 05 00 26 05 18 15 00 06 09 22 05 00 14 09 14 05 00 19 05 22 05 14 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 20 23 05 14 20 25 00 20 23 05 14 20 25 06 09 22 05 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 06 20 05 05 14 00 26 05 18 15 00 19 09 24 00 14 09 14 05 00 20 23 05 14 20 25 20 23 15 00 06 09 22 05 00 26 05 18 15 00 06 09 22 05 00 14 09 14 05 00 19 05 22 05 14 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 06 20 05 05 14 00 26 05 18 15 00 19 09 24 00 14 09 14 05 00 19 09 24 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 06 15 21 20 05 05 14 00 14 09 14 05 00 06 15 21 20 05 05 14 00 06 09 22 05 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 06 15 21 20 05 05 14 00 14 09 14 05 00 06 15 21 20 05 05 14 00 06 09 22 05 00 26 05 18 15 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 20 23 05 14 20 25 00 20 23 05 14 20 25 06 09 22 05 00 26 05 18 15 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 20 23 05 14 20 25 00 20 23 05 14 20 25 06 09 22 05 00 19 09 24 00 14 09 14 05 00 20 23 05 14 20 25 20 23 15 00 06 09 22 05 00 26 05 18 15 00 20 23 05 14 20 25 19 09 24 00 06 09 22 05 00 05 09 07 20 05 05 14 00 06 09 06 20 05 05 14 00 26 05 18 15 00 06 09 06 20 05 05 14 00 06 15 21 20 05 05 14 00 06 09 22 05 00 26 05 18 15 00 19 09 24 00 06 09 06 20 05 05 14 00 20 23 05 14 20 25 15 14 05 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 19 09 24 00 06 09 06 20 05 05 14 00 20 23 05 14 20 25 15 14 05 00 05 09 07 20 05 05 14 00 26 05 18 15 00 20 23 05 14 20 25 19 09 24 00 06 09 22 05 00 05 09 07 20 05 05 14 00 06 09 06 20 05 05 14 00 26 05 18 15 00 14 09 14 05 20 05 05 14 00 14 09 14 05 00 20 23 05 14 20 25 06 15 21 18 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 06 09 22 05 00 14 09 14 05 00 19 05 22 05 14 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 19 09 24 00 14 09 14 05 00 19 09 24 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 22 05 00 20 23 05 12 22 05 00 20 23 05 14 20 25 20 23 15 00 06 09 22 05 00 26 05 18 15 00 06 15 21 20 05 05 14 00 14 09 14 05 00 06 15 21 20 05 05 14 00 06 09 22 05 00 26 05 18 15 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 20 23 05 14 20 25 00 20 23 05 14 20 25 06 09 22 05 00 19 09 24 00 06 09 06 20 05 05 14 00 20 23 05 14 20 25 15 14 05 00 05 09 07 20 05 05 14 00 26 05 18 15 00 06 15 21 20 05 05 14 00 14 09 14 05 00 06 15 21 20 05 05 14 00 06 09 22 05 00 26 05 18 15 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 20 23 05 14 20 25 00 20 23 05 14 20 25 06 09 22 05 00 26 05 18 15 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 20 23 05 14 20 25 00 20 23 05 14 20 25 06 09 22 05 00 19 09 24 00 14 09 14 05 00 20 23 05 14 20 25 20 23 15 00 06 09 22 05 00 26 05 18 15 00 20 23 05 14 20 25 19 09 24 00 06 09 22 05 00 05 09 07 20 05 05 14 00 06 09 06 20 05 05 14 00 26 05 18 15 00 20 23 05 14 20 25 00 05 09 07 08 20 00 14 09 14 05 00 05 09 07 20 05 05 14 00 20 23 05 14 20 25 00 20 23 05 14 20 25 06 09 22 05 00 06 09 22 05 00 14 09 14 05 00 19 05 22 05 14 00 05 09 07 08 20 00 20 23 05 14 20 25 00 26 05 18 15 00 20 23 05 14 20 25 00 05 09 07 08 20 00 14 09 14 05 00 05 09 07 20 05 05 14 00 20 23 05 14 20 25 00 20 23 05 14 20 25 06 09 22 05 00 19 09 24 00 06 09 06 20 05 05 14 00 20 23 05 14 20 25 15 14 05 00 05 09 07 20 05 05 14 00 26 05 18 15 00 20 23 05 14 20 25 19 09 24 00 06 09 22 05 00 05 09 07 20 05 05 14 00 06 09 06 20 05 05 14 00 26 05 18 15 00 06 09 22 05 00 14 09 14 05 00 19 05 22 05 14 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 19 09 24 00 14 09 14 05 00 19 09 24 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 19 09 24 00 14 09 14 05 00 20 23 05 14 20 25 20 23 15 00 06 09 22 05 00 26 05 18 15 00 19 09 24 00 06 09 06 20 05 05 14 00 20 23 05 14 20 25 15 14 05 00 05 09 07 20 05 05 14 00 26 05 18 15 00 20 23 05 14 20 25 00 20 23 05 14 20 25 20 08 18 05 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 20 23 05 14 20 25 00 20 23 05 14 20 25 06 09 22 05 00 19 09 24 00 14 09 14 05 00 20 23 05 14 20 25 20 23 15 00 06 09 22 05 00 26 05 18 15 00 20 23 05 14 20 25 19 09 24 00 06 09 22 05 00 05 09 07 20 05 05 14 00 06 09 06 20 05 05 14 00 26 05 18 15 00 14 09 14 05 20 05 05 14 00 06 09 22 05 00 20 23 05 14 20 25 20 23 15 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 06 09 22 05 00 14 09 14 05 00 19 05 22 05 14 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14 00 26 05 18 15 00 19 09 24 00 14 09 14 05 00 20 23 05 14 20 25 20 23 15 00 06 09 22 05 00 26 05 18 15 00 19 09 24 00 14 09 14 05 00 20 23 05 14 20 25 20 23 15 00 06 09 22 05 00 26 05 18 15 00 19 09 24 00 06 09 06 20 05 05 14 00 20 23 05 14 20 25 15 14 05 00 20 23 05 14 20 25 00 06 09 22 05 00 06 09 22 05 00 06 15 21 20 05 05 14".split()
subs_string = " abcdefghijklmnopqrstuvwxyz@@@0123456789"

first_pass = ""

ciphered_text.each do |i|
  first_pass += subs_string[i.to_i]
end

puts first_pass

mymap = {}
mymap['fouteen'] = 14
mymap['nine'] = 9
mymap['five'] = 5
mymap['twenty'] = 20 
mymap['zero'] = 0
mymap['six'] = 6
mymap['twentytwo'] = 22 
mymap['fifteen'] = 15
mymap['twentyone'] = 21
mymap['eigteen'] = 18
mymap['twentythree'] = 23 
mymap['twentyfive'] = 25
mymap['twelve'] = 12
mymap['twentysix'] = 26
mymap['eight'] = 8
mymap['seven'] = 7
mymap['nineteen'] = 19
mymap['twentyfour'] = 24
mymap['four'] = 4
mymap['three'] = 3
mymap['two'] = 2
mymap['six'] = 6
mymap['one'] = 1
mymap['sixteen'] = 16 
mymap['thirtyeight'] = 38 
mymap['thirtyfour'] = 34

second_pass = ""
first_pass.split.each do |i|
  second_pass += subs_string[mymap[i]]
end

puts second_pass

third_pass = ""
second_pass.split.each do |i|
  third_pass += subs_string[mymap[i]]
end

puts third_pass

Lo ideal sería ejecutar un bucle, pero decía el objecto mymap lo iba construyendo a en cada iteración. Y luego también tendrías que saber cuando parar, es decir, saber en que iteración el texto obtenido es legible y con sentido. Como ves sólo se necesitan 3 iteraciones para llegar a nuestra solución. El script, una vez ejecutado, imprime una línea por cada paso, siendo la última línea y por lo tanto nuestro flag:

sedulously eschew obfuscatory hyperverbosity and prolixity 84 roedy green

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