HMACContext in Godot – Complete Guide

Welcome to our detailed tutorial on working with the HMACContext class in Godot 4! If you’re diving into the world of game development, you’ll soon find that security is just as important as any other feature in your games. Whether you’re a budding developer or someone who’s been in the game for quite some time, understanding how to secure your game’s sensitive data is crucial. HMAC, or Keyed-Hash Message Authentication Code, is your trusty tool in this quest – and Godot 4’s HMACContext class makes this easier than ever. Ready to level up your skills? Let’s get started.

What is HMAC?

HMAC stands for Keyed-Hash Message Authentication Code, a specific type of message authentication code (MAC) involving a cryptographic hash function and a secret cryptographic key. It provides a way to check both the data integrity and the authenticity of a message, reassuring you that the information hasn’t been tampered with and is from a verified source.

What is the HMACContext Class for?

The HMACContext class in Godot 4 enables you to securely combine a secret key with your message data using a hashing function. It’s particularly useful for cases where you need to process your message in chunks, piece by piece, which is common in game development when dealing with online data transactions or large datasets.

Why Should I Learn It?

Understanding and employing HMAC can be a game-changer in your development career. By learning how to use the HMACContext class:

– You’ll add an extra layer of security to your games, protecting user data and your intellectual property.
– You’ll deepen your knowledge of Godot 4’s broader cryptographic features, ensuring you’re well-equipped for various development scenarios.
– You’ll be able to confidently implement data integrity checks in your multiplayer games or any other application where security is paramount.

With these compelling reasons to learn about HMAC in Godot 4, let’s dive into the coding and see HMACContext in action!

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Setting Up HMACContext

Before we can start using HMACContext, we need to set up our Godot project to handle cryptography. Here’s how you initialize the HMACContext class:

var hmac_context =

Now, choose your desired hash function and key. In this example, we’re using SHA-256:

const HashType = Crypto.HASH_SHA256
var key = "my_secret_key".to_utf8()
hmac_context.start(HashType, key)

It’s important that the key is kept secret and is of a high entropy to ensure strong security.

Processing Data with HMACContext

You can process data in chunks, which is perfect for large datasets or streams of data. Here’s how to process the message in blocks:

var data_chunk = "First part of the message".to_utf8()

data_chunk = "Second part of the message".to_utf8()

# Continue with more chunks as needed

This method is handy for games dealing with ongoing player data or loading levels in parts for better performance.

Finalizing the HMAC Value

After processing all the data chunks, you can finalize the HMAC value. The `finish()` method will return the HMAC as a PoolByteArray:

var hmac_result = hmac_context.finish()

This HMAC value ensures that the complete message is verified as authentic and untampered with.

Verifying a Message with HMAC

If you receive a message and you want to verify it using the HMAC value, you can perform the same steps as before with the sender’s public HMAC value:

# Initialize HMACContext with the same key and hash function
hmac_context.start(Crypto.HASH_SHA256, key)

# Update the context with the received message data
hmac_context.update("Received message data here".to_utf8())

# Finish the HMAC process to get a value for comparison
var received_hmac = hmac_context.finish()

# Now compare this with the expected HMAC value
if received_hmac == "Expected HMAC value from sender":
    print("Message is verified!")
    print("Message verification failed!")

Remember, for a successful verification, the same secret key and hashing method used by the sender must be employed.

These basics give you a solid foundation for integrating HMAC into your Godot 4 projects. With these tools, you can handle messages securely, ensuring data integrity and authenticity in your game’s communications. In the next part, we’ll look at more advanced uses and potential pitfalls to watch out for when working with HMAC in Godot 4. Stay tuned for more expertise in securing your game’s data!Let’s explore more advanced uses of HMAC in Godot 4 and dive into potential pitfalls you might encounter.

Handling Different Hash Functions
The HMACContext class can work with different hash functions, such as SHA-1, SHA-256, or MD5. Keep in mind that more secure hash functions like SHA-256 are recommended. Here’s how you would use SHA-1:

hmac_context.start(Crypto.HASH_SHA1, key)

Be cautious when choosing your hash function, as some, like MD5 and SHA-1, are considered to be less secure.

Re-Initialising HMACContext for New Messages
You may want to use the same HMACContext for a different message. To do so, you need to re-initialise the context:

hmac_context.start(Crypto.HASH_SHA256, key)  # Restart HMACContext

Make sure to start with a fresh context to avoid any interference from previous data.

Serializing the HMAC Value
After generating the HMAC value, you might want to send it over a network or save it to a file. Here’s how you convert it to a hex string for easy serialization:

var hmac_hex = PoolByteArray(hmac_result).hex_encode()

To deserialize, convert the hex string back to a PoolByteArray:

var received_hmac = PoolByteArray(hex_to_raw("received hex string"))

Comparing HMAC Values
When comparing HMAC values, it’s important to compare them in a way that avoids potential timing attacks. Avoid doing direct comparison with ‘==’. Use the built-in secure compare method instead:

if hmac_context.verify("expected HMAC value".to_utf8(), received_hmac):
    print("HMAC values match, message verified!")
    print("Mismatch in HMAC values, message verification failed!")

Working with Binary Data
HMACContext can work with both text and binary data. Here’s an example of updating the HMAC with binary data:

var binary_data = PoolByteArray([0, 1, 2, 3, 4, 5])

# Follow with hmac_context.finish() when all data is processed

Error Handling
Always be prepared to handle errors in cryptographic operations. For instance, an incorrect initialization can throw errors:

var hmac_context =
if not hmac_context.start(Crypto.HASH_SHA256, key):
    push_error("Failed to initialize HMACContext with given key")

Pay attention to error messages, as they provide valuable clues about what might have gone wrong.

Use Cases in Game Development
Finally, let’s consider some real-world scenarios where you might use the HMACContext class in your games:

– Securely saving and verifying player scores or save data to prevent cheating.
– Authenticating messages between clients and servers in multiplayer games.
– Validating in-app purchases or downloadable content (DLC).

Remember that the HMACContext class offers a powerful way to secure your game’s data, but it’s only as strong as your implementation and understanding of its usage and limitations. Always consider the context of your application and use strong, unpredictable keys for the best security.

Through these examples and tips, you now have a greater arsenal to work with HMAC in Godot 4. Armed with these techniques, you can ensure the security of your game’s data, giving you and your players peace of mind. Stay secure and happy coding!Keeping in mind the important role that HMAC plays in securing data, it’s valuable to look at a few more practical examples where this can be applied in your Godot 4 projects. Here’s an assortment of code snippets showcasing various scenarios:

Generating HMAC for Peer-to-Peer Communication
In a peer-to-peer gaming scenario, you may want to ensure that communications between players are secure. Here’s how you can generate an HMAC for a message being sent from one peer to another:

var message = "Attack at dawn!"
var message_data = message.to_utf8()
hmac_context.start(Crypto.HASH_SHA256, key)
var message_hmac = hmac_context.finish()

You would then send both the `message_data` and the `message_hmac` to the peer, who would verify the HMAC before accepting the message as authentic.

Verifying In-Game Assets
When loading in-game assets such as textures or models, particularly if they come from an external source, you might want to verify their integrity:

var asset_data = load_external_asset("path_to_asset")
hmac_context.start(Crypto.HASH_SHA256, key)
var asset_hmac = hmac_context.finish()

if hmac_context.verify(expected_asset_hmac, asset_hmac):
    print("Asset is verified and safe to use")
    print("Asset verification failed, possible tampering detected")

Working with User Credentials
Let’s say you’re sending a user’s login information to your game server. It’s crucial to protect this sensitive data:

var username = "player1"
var password = "secret"
var credentials_data = (username + password).to_utf8()
hmac_context.start(Crypto.HASH_SHA256, key)
var credentials_hmac = hmac_context.finish()

Send the HMAC along with the username to the server, where it can be verified against the stored HMAC for that user.

Batch Processing Game Events
If you’re sending a batch of game events to be processed, you might want to create an HMAC for the entire batch for efficiency:

var event_batch = []
# Collect events into batch
# ...

for event in event_batch:
    var event_data = str(event).to_utf8()

var batch_hmac = hmac_context.finish()

When the event batch is received, you’ll use the HMAC value to verify that none of the events were altered during transmission.

Storing and Loading HMAC Values
There are scenarios where you’ll need to store the HMAC and load it later for verification purposes:

# Storing the HMAC value
var file ="user://hmac_value.dat", File.WRITE)

# Loading the HMAC value for verification"user://hmac_value.dat", File.READ)
var stored_hmac = file.get_buffer(file.get_len())

Ensure that the storage and retrieval of the HMAC value are done securely to maintain the value’s confidentiality and integrity.

Maintaining State across Scenes
In Godot, you often need to maintain state across different scenes. You can use an HMAC to ensure that the state data hasn’t been tampered with:

func save_game_state(state):
    # ... Prepare the game state data
    hmac_context.start(Crypto.HASH_SHA256, key)
    var state_hmac = hmac_context.finish()

func load_game_state(expected_hmac):
    # ... Load the game state data
    hmac_context.start(Crypto.HASH_SHA256, key)
    if hmac_context.verify(expected_hmac, hmac_context.finish()):
        # State is verified, continue loading
        # Verification failed, handle accordingly

Integrating Godot 4’s HMACContext class in these ways can safeguard your game’s data against tampering and unauthorized access. It’s a strong step towards establishing trust in your game’s systems and preserving the integrity of the player’s experience. Keep exploring with these examples as a foundation, and remember, mastering these techniques can make a substantial difference in the security of your games.

Continue Your Game Development Journey

With the knowledge of HMACContext in Godot 4 under your belt, you’re well on your way to mastering the security aspects of game development. But this is just the beginning; there’s a whole world of game creation waiting for you to explore. To keep the momentum going and further develop your skill set, we invite you to check out our Godot Game Development Mini-Degree. This comprehensive program guides you through the ins and outs of building cross-platform games, covering topics from essential to advanced, which can help you create a diverse portfolio of real projects.

Whether you’re just starting or looking to enhance your existing skills, Zenva offers a spectrum of courses that cater to different levels of experience. Our collection of Godot courses is designed to be flexible, providing you with the ability to learn at your own pace and on your own schedule. Engage with robust course content and gain practical skills through project-based learning, all while working towards earning completion certificates.

We’re constantly updating our curriculum to keep up with the latest trends and technologies in the game development world, ensuring you learn the most current and in-demand skills. So, take the next step in your game development journey with Zenva, and continue to build, create, and innovate in the exciting world of games.


As you’ve seen, mastering the HMACContext in Godot 4 doesn’t just boost your game’s security; it elevates your entire approach to game development. Every step towards enhancing your skills is a step towards crafting experiences that stand out in the digital era. Remember, it’s not just about making games—it’s about making games that resonate with audiences and remain secure and reliable in a world where digital safety is paramount.

Don’t stop here. Continue to harness the full potential of Godot 4 and other game development tools with our Godot Game Development Mini-Degree. It’s your gateway to transforming your ideas into reality and joining the ranks of creators who are shaping the future of gaming. At Zenva, we’re always here to provide you with quality education that’s engaging, accessible, and empowers you to turn your creative visions into playable, enjoyable, and secure game experiences.

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