Data encryption basics in Unity - Mini Project: Build & Apply

Data encryption basics

📖 Scenario: You are building a simple Unity game that needs to save player scores securely. To keep scores safe, you will encrypt the score data before saving it.

🎯 Goal: Create a Unity script that encrypts and decrypts a player's score using a basic encryption method.

📋 What You'll Learn

Create an integer variable called playerScore with the value 100

Create a string variable called encryptionKey with the value "key123"

Write a method called EncryptScore that takes playerScore and encryptionKey and returns an encrypted string

Write a method called DecryptScore that takes the encrypted string and encryptionKey and returns the original score as an integer

💡 Why This Matters

🌍 Real World

Encrypting player data helps protect game progress and scores from cheating or tampering.

💼 Career

Understanding basic encryption is useful for game developers and software engineers to secure sensitive data.

1

Set up player score variable

Create an integer variable called playerScore and set it to 100 inside a Unity MonoBehaviour class.

Unity

using UnityEngine;

public class ScoreEncryption : MonoBehaviour
{
    // Create playerScore variable
    // Your code here
}

Hint

Use int playerScore = 100; inside the class but outside any method.

2

Add encryption key variable

Add a string variable called encryptionKey and set it to "key123" inside the ScoreEncryption class.

Unity

using UnityEngine;

public class ScoreEncryption : MonoBehaviour
{
    int playerScore = 100;
    // Create encryptionKey variable
    // Your code here
}

Hint

Use string encryptionKey = "key123"; inside the class but outside any method.

3

Create EncryptScore method

Write a method called EncryptScore that takes an integer score and a string key, and returns a string. Use a simple encryption by converting the score to a string and appending the key.

Unity

using UnityEngine;

public class ScoreEncryption : MonoBehaviour
{
    int playerScore = 100;
    string encryptionKey = "key123";

    // Write EncryptScore method
    // Your code here
}

Hint

Define EncryptScore to return score.ToString() + key.

4

Create DecryptScore method

Write a method called DecryptScore that takes a string encrypted and a string key, removes the key from the end of encrypted, and returns the original score as an integer.

Unity

using UnityEngine;

public class ScoreEncryption : MonoBehaviour
{
    int playerScore = 100;
    string encryptionKey = "key123";

    string EncryptScore(int score, string key)
    {
        return score.ToString() + key;
    }

    // Write DecryptScore method
    // Your code here
}

Hint

Use Substring to remove the key and int.Parse to convert back to integer.

Practice

1. What is the main purpose of encryption in Unity programming?

easy

A. To create graphics effects

B. To convert readable data into a secret code to protect it

C. To make the game run faster

D. To store data in plain text files

Solution

1. Step 1: Understand what encryption does

   Encryption changes readable data into a secret code so others cannot understand it easily.

2. Step 2: Identify the purpose in Unity

   In Unity, encryption is used to protect sensitive information like passwords or personal data.

3. Final Answer:

   To convert readable data into a secret code to protect it -> Option B

4. Quick Check:

   Encryption = data protection [OK]

Hint: Encryption means hiding data by coding it [OK]

Common Mistakes:

• Thinking encryption makes the game faster
• Confusing encryption with graphics or speed
• Believing encryption stores data as plain text

2. Which of the following is the correct way to declare an AES encryption object in Unity C#?

easy

A. Aes aes = Create.Aes();

B. aes = new AES();

C. Aes aes = Aes.Create();

D. Aes aes = new Aes();

Solution

1. Step 1: Recall AES object creation in C#

   In C#, AES encryption objects are created using the static method Aes.Create().

2. Step 2: Check syntax correctness

   Aes aes = Aes.Create(); uses correct syntax: Aes aes = Aes.Create(); Options A, B, and C use incorrect constructors or methods.

3. Final Answer:

   Aes aes = Aes.Create(); -> Option C

4. Quick Check:

   Aes.Create() creates AES object [OK]

Hint: Use Aes.Create() to make AES object [OK]

Common Mistakes:

• Trying to use 'new AES()' which is invalid
• Using wrong capitalization like 'AES' instead of 'Aes'
• Calling non-existent methods like Create.Aes()

3. Consider this Unity C# code snippet for AES encryption:

using System.Security.Cryptography;
using System.Text;

Aes aes = Aes.Create();
aes.Key = Encoding.UTF8.GetBytes("1234567890123456");
aes.IV = Encoding.UTF8.GetBytes("abcdefghijklmnop");

byte[] encrypted;
using (var encryptor = aes.CreateEncryptor())
{
    byte[] input = Encoding.UTF8.GetBytes("HelloWorld");
    encrypted = encryptor.TransformFinalBlock(input, 0, input.Length);
}

string result = Convert.ToBase64String(encrypted);
Console.WriteLine(result);

What will be the output type of result?

medium

A. An error because of wrong key size

B. The original string 'HelloWorld'

C. A byte array of the encrypted data

D. A base64 encoded string representing encrypted data

Solution

1. Step 1: Understand encryption output

   The encrypted data is a byte array, which is then converted to a base64 string for easy display.

2. Step 2: Analyze the code's final output

   The code uses Convert.ToBase64String(encrypted) to get a string representation of encrypted bytes, so result is a base64 string.

3. Final Answer:

   A base64 encoded string representing encrypted data -> Option D

4. Quick Check:

   Encrypted bytes -> base64 string [OK]

Hint: Encrypted bytes are shown as base64 strings [OK]

Common Mistakes:

• Thinking output is original text
• Expecting byte array instead of string
• Assuming key size error without checking length

4. This Unity C# code tries to decrypt data but throws an exception:

byte[] encryptedData = ...;
Aes aes = Aes.Create();
aes.Key = Encoding.UTF8.GetBytes("shortkey");
aes.IV = Encoding.UTF8.GetBytes("shortiv");

using (var decryptor = aes.CreateDecryptor())
{
    byte[] decrypted = decryptor.TransformFinalBlock(encryptedData, 0, encryptedData.Length);
}

What is the main problem causing the error?

medium

A. The key and IV sizes are too short for AES

B. The encryptedData array is empty

C. CreateDecryptor() cannot be used without a password

D. TransformFinalBlock requires a string input

Solution

1. Step 1: Check key and IV sizes for AES

   AES requires keys and IVs of specific lengths (e.g., 16 bytes for AES-128). The given strings "shortkey" and "shortiv" are too short.

2. Step 2: Understand error cause

   Using keys or IVs with incorrect length causes exceptions during encryption/decryption.

3. Final Answer:

   The key and IV sizes are too short for AES -> Option A

4. Quick Check:

   Key/IV length must match AES requirements [OK]

Hint: AES keys and IVs must be exact length [OK]

Common Mistakes:

• Assuming encryptedData is empty without checking
• Thinking CreateDecryptor needs password parameter
• Believing TransformFinalBlock accepts strings directly

5. You want to securely store user passwords in Unity using AES encryption. Which approach is best practice?

hard

A. Encrypt passwords with AES and store the encrypted string with a unique IV per user

B. Store passwords as plain text for easy retrieval

C. Use a fixed key and IV for all users to simplify encryption

D. Encrypt passwords with AES but reuse the same IV for all users

Solution

1. Step 1: Understand secure password storage

   Passwords should never be stored as plain text. Encryption with AES is good, but IV must be unique per encryption to prevent attacks.

2. Step 2: Evaluate options for key and IV usage

   Using a unique IV per user with AES encryption improves security. Reusing IV or fixed keys weakens protection.

3. Final Answer:

   Encrypt passwords with AES and store the encrypted string with a unique IV per user -> Option A

4. Quick Check:

   Unique IV + AES = secure password storage [OK]

Hint: Always use unique IVs with AES encryption [OK]

Common Mistakes:

• Storing passwords as plain text
• Reusing IVs for all encryptions
• Using fixed keys for all users