CAPTCHAs, while designed to distinguish between humans and bots, can be a frustrating experience for users. They're often difficult to decipher, visually impaired users struggle with them, and they can interrupt the flow of the user journey. So, what's the alternative? Enter the world of custom puzzle verification, a powerful technique you can implement in your Django applications to create a more engaging and user-friendly security layer.

This post will explore how you can build your own puzzle system in Django, offering a more accessible and often more effective way to thwart bots without resorting to CAPTCHAs.

Why Puzzles?

Well-designed puzzles can be:

• User-Friendly: They can be fun and engaging, turning security checks into a less tedious experience.
• Accessible: Puzzles can be designed to be accessible to users with disabilities, unlike some CAPTCHA implementations.
• Bot-Resistant: While bots are becoming more sophisticated, well-chosen puzzles can still pose a significant challenge.

Building Your Puzzle System in Django:

The key is to combine Django's form handling capabilities with Python's versatility for puzzle generation.

1. Puzzle Generation:

This is where you get creative! Here are a few puzzle ideas and how to generate them:

• Math Problems: Simple arithmetic can be surprisingly effective.

  import random
  
  def generate_math_puzzle():
      num1 = random.randint(1, 20)
      num2 = random.randint(1, 20)
      operator = random.choice(["+", "-"])
      question = f"{num1} {operator} {num2} = ?"
      answer = eval(f"{num1} {operator} {num2}")  # Use with caution!
      return question, answer
  

  • Important Security Note: While eval() works for simple math, be extremely cautious when using it with user-provided input. For more complex calculations, consider using safer alternatives like ast.literal_eval().

• Image-Based Puzzles: Ask users to identify shapes or objects.

  from PIL import Image, ImageDraw
  import random
  import base64
  from io import BytesIO
  
  def generate_shape_puzzle():
      image = Image.new("RGB", (100, 100), "white")
      draw = ImageDraw.Draw(image)
      shape = random.choice(["rectangle", "circle"])  # Add more shapes
      # ... (Draw the shape on the image) ...
  
      # Encode the image to base64 for display in the template
      buffered = BytesIO()
      image.save(buffered, format="PNG")
      img_str = base64.b64encode(buffered.getvalue()).decode()
  
      answer = shape
      return img_str, answer
  

• Word Puzzles: Anagrams or missing letters.

  import random
  
  def generate_anagram_puzzle():
      word = random.choice(["python", "django"])
      anagram = list(word)
      random.shuffle(anagram)
      question = f"Unscramble: {''.join(anagram)}"
      answer = word
      return question, answer
  

2. Django Integration:

• Forms: Create a Django form to display the puzzle and receive the user's answer.

  from django import forms
  
  class PuzzleForm(forms.Form):
      answer = forms.CharField(label="Answer")
  

• Views: Generate the puzzle, store the answer securely (e.g., in the session), and process the user's submission.

  from django.shortcuts import render, redirect
  from .forms import PuzzleForm
  from .puzzle_generator import generate_math_puzzle  # Or any other puzzle function
  
  def my_view(request):
      question, correct_answer = generate_math_puzzle()  # Choose your puzzle type
      request.session['correct_answer'] = correct_answer
  
      if request.method == 'POST':
          form = PuzzleForm(request.POST)
          if form.is_valid():
              user_answer = form.cleaned_data['answer']
              if str(user_answer) == str(request.session.get('correct_answer')):
                  # Success! Redirect or process the form
                  return redirect('success_page')
              else:
                  form.add_error('answer', "Incorrect answer. Try again.") # Display error
      else:
          form = PuzzleForm(initial={'question': question})
  
      return render(request, 'my_template.html', {'form': form, 'question': question})
  

• Templates: Display the puzzle and the form.

  <form method="post">
      {% csrf_token %}
      <p>{{ question }}</p>  {# Display the puzzle question #}
      {{ form.answer.label_tag }} {{ form.answer }} {{ form.answer.errors }}
      <button type="submit">Submit</button>
  </form>
  

3. Security Best Practices:

• Secure Answer Storage: Never store the correct answer in client-side code. Use Django sessions or a database.
• Rate Limiting: Implement rate limiting to prevent brute-force attacks.
• Puzzle Variety: Vary the puzzles frequently.
• Combine Approaches: Combine puzzles with other bot-mitigation techniques (e.g., honeypots, time-based checks) for stronger security.

Conclusion:

By implementing a custom puzzle system, you can create a more user-friendly and engaging experience while improving the security of your Django application. Remember to choose puzzles that are easy for humans but difficult for bots, and always prioritize security best practices. With a little creativity, you can move beyond CAPTCHAs and create a truly unique and effective bot-deterrent system.