Welcome to the CTF Game!

Rules

1. Each stage contains a unique encrypted message that you must decode to proceed to the next stage.
2. You must complete each stage sequentially; you cannot skip stages.
3. Use the provided hints and instructions to decode the messages correctly.
4. Submit your decoded message in the input field provided on each stage page.
5. No external tools or scripts are allowed unless explicitly mentioned in the instructions.
6. Maintain the integrity of the game by not sharing answers with other participants.

Tips

• Keep a pen and paper, and a calculator (or your smartphone's calculator) if needed, handy.
• Don't forget to write somewhere, the decoded text you get in each round.
• Read the instructions carefully for each stage; they will guide you on how to decode the message.
• Practice decoding messages manually to enhance your cryptography skills.
• Use online resources for reference, but ensure you understand how each cipher works.
• Take notes as you progress through each stage to help you identify patterns and techniques.
• Stay patient and persistent; some stages may be more challenging than others.

Understanding Modulus Operation

The modulus operation finds the remainder when one integer is divided by another. The syntax is typically a % b (read as 'a mod b'), where a is the dividend and b is the divisor.

Quotient × Divisor + Remainder = Dividend

Example with Positive Number:

    29 % 7
    
    1. Divide 29 by 7, quotient = 4 (consider only integer part)
    2. Multiply 4 by 7, result = 28
    3. Subtract 28 from 29, remainder = 1
    
    Result: 29 % 7 = 1

Example with Negative Number:

    -6 % 26
    
    1. Divide -6 by 26, quotient = -1 (consider only integer part)
    2. Multiply -1 by 26, result = -26
    3. Subtract -26 from -6, remainder = 20
    
    Result: -6 % 26 = 20
            

Simple trick to perform modulus operation on a negative number:

    -32 % 7
    
    Add the divisor (here, 7) to the dividend (here, -32) repeatedly
    until you get a positive number.
    
    -32 + 7 = -25
    -25 + 7 = -18
    -18 + 7 = -11
    -11 + 7 = -4
    -4 + 7 = 3

    When you stop getting negative numbers and obtain the first
    positive number, that positive number is the remainder, ie, 
    the result of the modulus operation.

            

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