The Numbers

Challenge

The challenge provides an image containing a sequence of numbers and curly braces, with a noisy, splattered background.

The numbers presented are: 16 9 3 15 3 20 6 { 20 8 5 14 21 13 2 5 18 19 13 1 19 15 14 }

Analysis

The core of this challenge is recognizing the pattern in the data provided. Several clues point toward the solution:

1. Numeric Data: The data consists entirely of numbers.
2. Range of Numbers: All numbers fall between 1 and 26. This is a strong indicator of a substitution cipher where each number maps to a letter of the English alphabet.
3. Standard CTF Format: The presence of curly braces {} strongly suggests the standard picoCTF{flag_goes_here} format. The numbers outside the braces likely spell out picoCTF.

This pattern is characteristic of the A1Z26 cipher, where A=1, B=2, C=3, and so on, up to Z=26.

Solution

To solve the cipher, we substitute each number with its corresponding letter in the alphabet.

Let's break it down:

Part 1: The prefix

• 16 -> P
• 9 -> I
• 3 -> C
• 15 -> O
• 3 -> C
• 20 -> T
• 6 -> F

This spells out PICOCTF, confirming our suspicion about the flag format.

Part 2: The flag content

• 20 -> T
• 8 -> H
• 5 -> E
• 14 -> N
• 21 -> U
• 13 -> M
• 2 -> B
• 5 -> E
• 18 -> R
• 19 -> S
• 13 -> M
• 1 -> A
• 19 -> S
• 15 -> O
• 14 -> N

This sequence decodes to THE NUMBERS MASON. This is a famous quote from the video game Call of Duty: Black Ops.

Flag

Combining the parts and formatting it as a standard flag (usually with underscores instead of spaces), we get the final answer.