Identicon

The Mystery of Identicons: Turning Data into Unique Visual Avatars

Introduction

If you’ve ever signed up for a new website and seen a colorful, pixelated avatar appear next to your name — without uploading a profile picture — you’ve probably met an Identicon.

Identicons are unique, algorithmically generated images based on a piece of text, usually a username, email, or IP address. They are used for visual identification and uniqueness without revealing personal information.

Where Do We See Identicons?

• GitHub: User avatars when no profile picture is uploaded.
• WordPress: Default avatars for comments.
• StackOverflow: Generated icons for users without a custom profile picture.

How Do Identicons Work?

1. Hashing the Input – The text (e.g., "kiyotaka ayanokōji") is passed through a hash function like SHA1 or MD5, producing a fixed-length hexadecimal value.
2. Mapping Bits to a Grid – The hash is split into smaller parts, each controlling a color or pattern. Many identicons are symmetrical for aesthetic reasons.
3. Drawing the Image – The colored blocks are placed on a grid (e.g., 5x5) to form the final avatar.

Why Use Identicons?

• Uniqueness: Two different inputs create different images.
• Anonymity: Shows a unique avatar without revealing the actual input.
• Lightweight: No need to store user-uploaded images.
• Fun Factor: Adds personality to otherwise plain usernames.

Generating Identicons in Python

We can use the pydenticon library.

	pip install pydenticon

Example Code:

  
  import pydenticon
  import hashlib

  # Configure the identicon generator
  generator = pydenticon.Generator(
      5, 5, digest=hashlib.sha1,
      foreground=["#1abc9c", "#3498db", "#9b59b6", "#f1c40f", "#e67e22", "#e74c3c"],
      background="#ecf0f1"
  )

  # Input data
  username = "Kiyotaka"

  # Generate identicon image (PNG format)
  identicon_png = generator.generate(username, 200, 200, output_format="png")

  # Save to file
  with open("identicon.png", "wb") as f:
      f.write(identicon_png)

  print("Identicon saved as identicon.png")
  

Can You Decode an Identicon?

No — identicons are one-way just like hashes. You can generate an identicon from a string, but you can’t get the original string from the image. However, you can guess inputs and check if the generated identicon matches (similar to hash cracking).

Limitations

• Not cryptographically secure for authentication.
• If parameters (colors, grid size, hash function) are unknown, matching is hard.
• Similar-looking inputs can produce visually similar identicons.

Fun Experiments

• Generate identicons from movie character names.
• Create a web service that shows an identicon for each visitor’s IP.
• Use identicons in a chat app for quick user distinction.

Conclusion

Identicons are a perfect blend of data, art, and security concepts. They take something abstract like a hash and turn it into a friendly visual identity. Next time you see one, you’ll know there’s a hash hiding behind those colorful squares.

Pro Tip: Try generating identicons for your friends’ names and see if they can guess whose is whose.