This experiment guides you through the process of analyzing and breaking mono-alphabetic substitution ciphers using frequency analysis and pattern recognition techniques.

Part 1: Ciphertext Analysis

STEP 1: Load a ciphertext sample by clicking the "📝 Next Ciphertext" button to cycle through different encrypted messages.

STEP 2: Examine the English Letter Frequencies reference table provided. Note that 'e' is the most frequent letter (12.702%), followed by 't' (9.056%) and 'a' (8.167%).

STEP 3: Click "📊 Calculate Frequencies" to analyze the letter frequency distribution in the current ciphertext.

STEP 4: Compare the ciphertext frequencies with standard English letter frequencies to identify potential substitutions. The most frequent letter in the ciphertext likely corresponds to 'e' in the plaintext.

Part 2: Interactive Substitution Workspace

STEP 5: In the Working Area, you'll see a copy of the ciphertext that you can modify through substitutions.

STEP 6: Use the Substitution Tools to replace cipher characters with plaintext letters:

• Enter a cipher character (lowercase) in the first field
• Enter the corresponding plaintext character (uppercase) in the second field
• Click "✓ Apply" to make the substitution throughout the text

STEP 7: Monitor your Replacement History to track all substitutions you've made.

STEP 8: Use the "⟲ Replace" function to substitute phrases or character sequences if needed.

STEP 9: Continue making substitutions based on:

• Frequency analysis results
• Common English letter patterns (th, er, on, an, etc.)
• Word structure and context clues

Part 3: Solution Verification

STEP 10: Once you believe you have the correct plaintext, copy your decrypted text to the "📝 Final Plaintext" field.

STEP 11: Enter the complete substitution key (26 characters) in the "🔑 Solution Key" field, representing the cipher alphabet that maps to the standard alphabet a-z.

STEP 12: Click "✅ Check Answer" to verify your solution against the correct answer.

STEP 13: Review the feedback provided:

• ✅ Correct solutions will be confirmed with success message
• ❌ Incorrect solutions will show hints and the expected output for learning

Part 4: Advanced Analysis

STEP 14: Use the "🔄 Reset Workspace" button to clear all substitutions and start fresh with the same ciphertext.

STEP 15: Try different approaches:

• Start with the most frequent letters
• Look for common short words (a, an, the, and, etc.)
• Identify repeated letter patterns

STEP 16: Practice with multiple ciphertexts by using "📝 Next Ciphertext" to load different encrypted messages and improve your cryptanalysis skills.

Tips for Success:

• Frequency Analysis: Always start by comparing letter frequencies
• Pattern Recognition: Look for common English letter combinations
• Systematic Approach: Keep track of your substitutions and reasoning
• Context Clues: Use partial words to guess missing letters
• Verification: Regularly check if your partial decryption makes sense in English