Data encryption basics in Unity - Step-by-Step Execution

Concept Flow - Data encryption basics

Start with plain data

↓

Choose encryption key

↓

Apply encryption algorithm

↓

Get encrypted data

↓

Store or send encrypted data

↓

To decrypt: use same key

↓

Apply decryption algorithm

↓

Retrieve original plain data

This flow shows how plain data is encrypted using a key and algorithm, then decrypted back to original data using the same key.

Execution Sample

Unity

using System;
using System.Text;

string Encrypt(string text, string key) {
  // Simplified example
  return Convert.ToBase64String(Encoding.UTF8.GetBytes(text));
}

This simple code converts text to bytes and encodes it as base64 to simulate encryption.

Execution Table

Step	Action	Input	Output	Notes
1	Start with plain text	"Hello"	"Hello"	Original data to encrypt
2	Choose key	"myKey123"	"myKey123"	Key used for encryption
3	Convert text to bytes	"Hello"	[72, 101, 108, 108, 111]	UTF8 bytes of text
4	Convert bytes to Base64 string	[72, 101, 108, 108, 111]	"SGVsbG8="	Simulated encrypted data
5	Output encrypted data	"SGVsbG8="	"SGVsbG8="	Encrypted text ready to store or send
6	Decrypt: Convert Base64 to bytes	"SGVsbG8="	[72, 101, 108, 108, 111]	Reverse conversion
7	Convert bytes to text	[72, 101, 108, 108, 111]	"Hello"	Original text recovered

💡 Decryption completes when original text is recovered from encrypted data.

Variable Tracker

Variable	Start	After Step 3	After Step 4	After Step 6	Final
plainText	"Hello"	"Hello"	"Hello"	"Hello"	"Hello"
key	null	"myKey123"	"myKey123"	"myKey123"	"myKey123"
byteData	null	[72, 101, 108, 108, 111]	[72, 101, 108, 108, 111]	[72, 101, 108, 108, 111]	[72, 101, 108, 108, 111]
encryptedText	null	null	"SGVsbG8="	"SGVsbG8="	"SGVsbG8="
decryptedText	null	null	null	"Hello"	"Hello"

Key Moments - 3 Insights

Why do we convert text to bytes before encryption?

Computers work with bytes, not text directly. Step 3 shows text converted to bytes so encryption algorithms can process it.

Is the base64 string the real encrypted data?

In this example, base64 is just encoding bytes to text for easy storage/transfer (Step 4). Real encryption would transform bytes securely.

Why do we need the same key to decrypt?

Encryption uses the key to scramble data. Decryption uses the same key to unscramble it.

Visual Quiz - 3 Questions

Look at the execution table, what is the output after Step 4?

A [72, 101, 108, 108, 111]

B "Hello"

C "SGVsbG8="

D null

💡 Hint

Check the Output column for Step 4 in the execution_table.

At which step do we convert the encrypted base64 string back to bytes?

A Step 3

B Step 6

C Step 2

D Step 7

💡 Hint

Look for the step where Base64 string is converted to bytes in the execution_table.

If we change the key, what will happen in the decryption steps?

A Decryption will fail to recover original text

B Decryption will still work fine

C Encryption will change but decryption stays same

D Key does not affect encryption or decryption

💡 Hint

Refer to key importance explained in key_moments.

Concept Snapshot

Data encryption basics:
- Convert plain text to bytes
- Use a secret key with an algorithm
- Encrypt bytes to secure data
- Store or send encrypted data
- Use same key to decrypt back
- Decryption recovers original text

Full Transcript

This visual trace shows how data encryption works step-by-step. We start with plain text, convert it to bytes because computers handle bytes, then apply an encryption process simulated here by base64 encoding. The encrypted data is stored or sent. To get the original text back, we decode the base64 string to bytes and convert bytes back to text. The key is essential to encrypt and decrypt correctly. Changing the key breaks decryption. This simple example helps understand the flow of encryption and decryption in programming.

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