ApocalypseCipher Manual

📖 Introduction

This guide will teach you how to encrypt messages using the Apocalypse Cipher method with only pencil, paper, and a printed copy of the Vigenère table. No computers required!

Encryption is the opposite of decryption. Instead of finding the ciphertext and working backward to find the plaintext, you'll start with your secret message and transform it into unreadable ciphertext.

🔄 Encryption vs Decryption: What's Different?

Encryption and decryption use the same table, but in opposite directions. Here's how they compare:

🔧 Understanding the Parameters

These settings define how your message gets transformed into ciphertext. Both sender and receiver must use the same settings to communicate!

⚖️ Security vs Convenience

Different settings balance security and usability. Choose based on your needs:

📊 The Vigenère Table

Your main tool for manual encryption. Print this table or draw it on paper before starting. The same table works for both encryption and decryption.

How to read for encryption: Find the key letter on the left (row), find the plaintext letter at the top (column), then read the ciphertext letter where that row and column meet.

📝 Step-by-Step Encryption Process

Follow these steps in order. Each step builds on the previous one.

1. Prepare Your Message

   First, decide if you want to preserve formatting:

   • Preserve Formatting ON: Keep your message exactly as-is (spaces, capitals, punctuation)
   • Preserve Formatting OFF: Convert to uppercase letters only, remove spaces/punctuation

   Example: "Hello World!"

   Preserve ON: H e l l o W o r l d ! Preserve OFF: HELLOWORLD
2. Write Down Your Message and Key

   Record everything you'll need for encryption:

   • Your (prepared) plaintext message
   • Your chosen passphrase
   • All parameter values
3. Write the Plaintext and Passphrase in Rows

   Create two rows of letters. Write your plaintext message on top, and repeat the passphrase below it.

   Example (Preserve Formatting OFF)

   Plaintext: H E L L O W O R L D Passphrase: S E C R E T S E C R

   The passphrase repeats to match each letter of your message.

4. Find Each Letter on the Vigenère Table

   For each letter, you'll combine the row (key) and column (plaintext) to get the ciphertext.

   The Encryption Rule

   Look at the PASSKEY letter (left side), find your PLAINTEXT letter at the top, then read the CIPHERTEXT letter where that row and column meet.

5. Encode Each Letter

   For each column of letters:

   • Find the passphrase letter in the left column (the row)
   • Find your plaintext letter at the top (the column)
   • Read the letter at the intersection — that's your ciphertext!
6. Record Your Ciphertext Letters

   Write down each encrypted letter below your plaintext row.

   Continuing the Example

   Plaintext: H E L L O W O R L D Passphrase: S E C R E T S E C R Ciphertext: Z V N Y E L J V T W
7. Handle Multiple Rounds

   If using more than 1 round:

   1. Complete the first round of encryption
   2. Use the ciphertext as the new "plaintext"
   3. Repeat the passphrase and encrypt again
   4. Continue until you've done all rounds

   Tip

   For manual encryption, 1-2 rounds is practical. Each round adds significant work but also significantly more security.

🎯 Complete Worked Example

Let's walk through a complete encryption together, step by step.

How Each Letter Was Encrypted:

⚙️ Handling Advanced Parameters

When using additional parameters, modify your approach as follows.

With Initial Shift (not 0):

The Initial Shift applies AFTER the Vigenère cipher:

1. First, encrypt using the Vigenère table
2. Then, shift each resulting letter FORWARD by the shift value
3. Example: If shift = 3, and you got "A", shift it forward to "D"

With Multiple Rounds:

Each round re-encrypts the previous result:

1. Round 1: Plaintext → Ciphertext 1
2. Round 2: Ciphertext 1 → Ciphertext 2
3. Round 3: Ciphertext 2 → Final Ciphertext

With Keyed Alphabet:

Create a custom cipher alphabet from your passphrase:

Replace the top header of your Vigenère table with this new alphabet. Both encryption and decryption use the same modified table.

With Reverse Passphrase:

Simply reverse your passphrase before using it:

⚡ Quick Reference

Print this box and keep it next to your Vigenère table for fast reference.

╔════════════════════════════════════════════════════════════════╗
║                    SIMPLIFIED ENCRYPTION                       ║
╠════════════════════════════════════════════════════════════════╣
║                                                                ║
║  1. PREPARE: Remove spaces/caps if Preserve Formatting = OFF   ║
║                                                                ║
║  2. WRITE: Plaintext on top, passphrase repeated below         ║
║                                                                ║
║  3. FIND: For each pair:                                       ║
║           • Look at the left column → Passphrase letter (row)  ║
║           • Find plaintext letter at the top (column)          ║
║           • Read where row & column meet → Ciphertext letter   ║
║                                                                ║
║  4. WRITE: Ciphertext letters as your final message            ║
║                                                                ║
║  5. IF Rounds > 1: Repeat steps 2-4 for each round             ║
║                                                                ║
╚════════════════════════════════════════════════════════════════╝

✅ Pre-Encryption Checklist

Before sending your encrypted message, make sure you have:

• The ciphertext (your encrypted message)
• The passphrase (share this securely!)
• Initial Shift value (if not 0, share this too!)
• Rounds value (if not 1, share this too!)
• Keyed Alphabet setting (if ON, share this too!)
• Reverse Passphrase setting (if ON, share this too!)
• Preserve Formatting setting (recipient must know!)
• A way to communicate parameters to the recipient

🔍 Troubleshooting