Data encryption basics in Unity - Performance & Optimization

Performance: Data encryption basics

MEDIUM IMPACT

This affects the time it takes to encrypt and decrypt data, impacting app responsiveness and load times when handling secure data.

Encrypting user data frequently during gameplay

Unity

using System.Security.Cryptography;

public class Encryptor {
    private Aes aes;
    private ICryptoTransform encryptor;

    public Encryptor(byte[] key, byte[] iv) {
        aes = Aes.Create();
        aes.Key = key;
        aes.IV = iv;
        encryptor = aes.CreateEncryptor(aes.Key, aes.IV);
    }

    public string EncryptData(string plainText) {
        using (MemoryStream ms = new MemoryStream()) {
            using (CryptoStream cs = new CryptoStream(ms, encryptor, CryptoStreamMode.Write)) {
                using (StreamWriter sw = new StreamWriter(cs)) {
                    sw.Write(plainText);
                }
                return Convert.ToBase64String(ms.ToArray());
            }
        }
    }
}

Reuses encryption objects to avoid repeated costly setup, reducing CPU spikes and improving responsiveness.

📈 Performance GainReduces blocking time to under 10ms per call, improving input responsiveness (INP)

Encrypting user data frequently during gameplay

Unity

using System.Security.Cryptography;

public string EncryptData(string plainText, byte[] key, byte[] iv) {
    using (Aes aes = Aes.Create()) {
        aes.Key = key;
        aes.IV = iv;
        ICryptoTransform encryptor = aes.CreateEncryptor(aes.Key, aes.IV);
        using (MemoryStream ms = new MemoryStream()) {
            using (CryptoStream cs = new CryptoStream(ms, encryptor, CryptoStreamMode.Write)) {
                using (StreamWriter sw = new StreamWriter(cs)) {
                    sw.Write(plainText);
                }
                return Convert.ToBase64String(ms.ToArray());
            }
        }
    }
}

Creates new encryption objects and streams every time, causing CPU spikes and blocking the main thread.

📉 Performance CostBlocks main thread for 50-100ms per call, causing input lag (INP) during gameplay

Performance Comparison

Pattern	CPU Usage	Main Thread Blocking	Responsiveness Impact	Verdict
Creating new encryptor each call	High CPU spikes	Blocks main thread 50-100ms	Causes input lag (INP)	[X] Bad
Reusing encryptor instance	Lower CPU spikes	Blocks main thread <10ms	Smooth input responsiveness	[OK] Good

Rendering Pipeline

Encryption runs on the CPU and can block the main thread if done synchronously, delaying UI updates and input handling.

→JavaScript Execution (if WebGL)

→Main Thread CPU

→Input Handling

⚠️ BottleneckMain Thread CPU blocking during encryption calls

Core Web Vital Affected

INP

This affects the time it takes to encrypt and decrypt data, impacting app responsiveness and load times when handling secure data.

Optimization Tips

1Avoid creating new encryption objects on every call to reduce CPU spikes.

2Perform encryption asynchronously or off the main thread to keep UI responsive.

3Reuse encryption instances to minimize setup overhead and improve input responsiveness.

Performance Quiz - 3 Questions

What is the main performance issue when creating new encryption objects every time you encrypt data in Unity?

A It causes high CPU usage and blocks the main thread, leading to input lag.

B It increases GPU load and slows down rendering.

C It reduces memory usage but increases network latency.

D It improves security but slows down disk access.

DevTools: Unity Profiler

How to check: Open Unity Profiler, record during encryption calls, look at CPU usage and main thread spikes.

What to look for: High CPU spikes and main thread blocking during encryption indicate poor performance.

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