Data encryption basics in Unity - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a new AES encryption object.

Unity

using System.Security.Cryptography;

Aes aes = Aes.[1]();

Drag options to blanks, or click blank then click option'

ACreate

BCreateEncryptor

CGenerateKey

DGenerateIV

Attempts:

3 left

💡 Hint

Common Mistakes

Using CreateEncryptor() instead of Create()

Trying to generate key or IV directly without creating AES object

The Aes.Create() method creates a new AES encryption object.

2fill in blank

medium

Complete the code to generate a random encryption key.

Unity

using System.Security.Cryptography;

Aes aes = Aes.Create();
aes.[1]();

Drag options to blanks, or click blank then click option'

AGenerateKey

BDispose

CGenerateIV

DCreateEncryptor

Attempts:

3 left

💡 Hint

Common Mistakes

Calling GenerateIV() instead of GenerateKey()

Calling CreateEncryptor() before generating key

The GenerateKey() method creates a new random key for encryption.

3fill in blank

hard

Fix the error in the code to create an encryptor with the AES key and IV.

Unity

using System.Security.Cryptography;

Aes aes = Aes.Create();
aes.GenerateKey();
aes.GenerateIV();
ICryptoTransform encryptor = aes.[1](aes.Key, aes.IV);

Drag options to blanks, or click blank then click option'

AGenerateKey

BCreateEncryptor

CGenerateIV

DCreateDecryptor

Attempts:

3 left

💡 Hint

Common Mistakes

Using CreateDecryptor instead of CreateEncryptor

Calling GenerateKey or GenerateIV instead of creating encryptor

The CreateEncryptor(key, iv) method creates an encryptor using the AES key and IV.

4fill in blank

hard

Fill both blanks to encrypt data using the encryptor and a CryptoStream.

Unity

using System.IO;
using System.Security.Cryptography;

byte[] data = new byte[] {1, 2, 3};
MemoryStream ms = new MemoryStream();
CryptoStream cs = new CryptoStream(ms, encryptor, [1]);
cs.[2](data, 0, data.Length);

Drag options to blanks, or click blank then click option'

ACryptoStreamMode.Write

BCryptoStreamMode.Read

CWrite

DRead

Attempts:

3 left

💡 Hint

Common Mistakes

Using CryptoStreamMode.Read instead of Write

Calling Read() instead of Write() on CryptoStream

To encrypt data, use CryptoStreamMode.Write and call Write() on the CryptoStream.

5fill in blank

hard

Fill all three blanks to decrypt data using a decryptor and CryptoStream.

Unity

using System.IO;
using System.Security.Cryptography;

byte[] encryptedData = new byte[] {5, 6, 7};
MemoryStream ms = new MemoryStream(encryptedData);
ICryptoTransform decryptor = aes.[1](aes.Key, aes.IV);
CryptoStream cs = new CryptoStream(ms, decryptor, [2]);
byte[] decrypted = new byte[encryptedData.Length];
cs.[3](decrypted, 0, decrypted.Length);

Drag options to blanks, or click blank then click option'

ACreateDecryptor

BCryptoStreamMode.Read

CRead

DCreateEncryptor

Attempts:

3 left

💡 Hint

Common Mistakes

Using CreateEncryptor instead of CreateDecryptor

Using CryptoStreamMode.Write instead of Read

Calling Write() instead of Read() on CryptoStream

To decrypt data, create a decryptor with CreateDecryptor, use CryptoStreamMode.Read, and call Read() on the CryptoStream.

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