Asymmetric encryption (RSA, ECC) in Cybersecurity - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the sentence to describe asymmetric encryption.

Cybersecurity

In asymmetric encryption, the [1] key is used to encrypt data.

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

Aprivate

Bpublic

Cshared

Dsecret

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing the private key as the one used for encryption.

Thinking both keys are the same.

The public key is used to encrypt data in asymmetric encryption, while the private key is used to decrypt it.

2fill in blank

medium

Complete the sentence to explain RSA key generation.

Cybersecurity

RSA key generation involves selecting two large [1] numbers.

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

Aprime

Beven

Ccomposite

Drandom

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing composite numbers instead of prime numbers.

Assuming any random number can be used.

RSA keys are generated by selecting two large prime numbers to create the public and private keys.

3fill in blank

hard

Fix the error in the explanation of ECC.

Cybersecurity

ECC uses [1] curves over finite fields for encryption.

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

Aelliptic

Bcircular

Cparabolic

Dlinear

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing elliptic with circular or linear curves.

Not knowing the type of curve ECC uses.

ECC stands for Elliptic Curve Cryptography, which uses elliptic curves over finite fields.

4fill in blank

hard

Fill both blanks to complete the description of asymmetric encryption keys.

Cybersecurity

The [1] key is kept secret, while the [2] key is shared publicly.

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

Aprivate

Bpublic

Cshared

Dencrypted

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up which key is public and which is private.

Thinking both keys are shared.

In asymmetric encryption, the private key is kept secret by the owner, and the public key is shared with others.

5fill in blank

hard

Fill all three blanks to complete the RSA encryption formula.

Cybersecurity

Ciphertext = (Plaintext [1] PublicKey) [2] Modulus; Decryption uses [3] key.

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

Araised to the power of

Bmod

Cprivate

Dmultiplied by

Attempts:

3 left

💡 Hint

Common Mistakes

Using multiplication instead of exponentiation.

Confusing which key is used for decryption.

RSA encryption raises the plaintext to the power of the public key exponent, then takes the modulus. Decryption uses the private key.

Practice

1. What is the main purpose of asymmetric encryption like RSA and ECC?

easy

A. To use the same key for both encrypting and decrypting

B. To store passwords in plain text

C. To use two different keys: one to encrypt and one to decrypt

D. To speed up internet connections

Solution

1. Step 1: Understand key usage in asymmetric encryption

   Asymmetric encryption uses two keys: a public key to encrypt and a private key to decrypt messages.

2. Step 2: Compare with symmetric encryption

   Symmetric encryption uses the same key for both encrypting and decrypting, which is different from asymmetric encryption.

3. Final Answer:

   To use two different keys: one to encrypt and one to decrypt -> Option C

4. Quick Check:

   Asymmetric encryption = two keys (public/private) [OK]

Hint: Remember: public key encrypts, private key decrypts [OK]

Common Mistakes:

• Confusing asymmetric with symmetric encryption
• Thinking one key is used for both encrypting and decrypting
• Believing encryption speeds up internet
• Assuming passwords are stored in plain text

2. Which of the following is a correct statement about RSA keys?

easy

A. RSA does not use any mathematical operations

B. RSA uses a single key for both encryption and decryption

C. RSA keys are always 128 bits long

D. RSA keys are generated using large prime numbers

Solution

1. Step 1: Recall RSA key generation method

   RSA keys are created by multiplying two large prime numbers to form the public and private keys.

2. Step 2: Check other options for correctness

   RSA does not use a single key, keys are not fixed at 128 bits, and it heavily relies on math operations.

3. Final Answer:

   RSA keys are generated using large prime numbers -> Option D

4. Quick Check:

   RSA key generation = large primes [OK]

Hint: RSA keys come from multiplying big prime numbers [OK]

Common Mistakes:

• Thinking RSA uses one key only
• Assuming RSA keys have fixed small size
• Ignoring the role of prime numbers
• Believing RSA avoids math operations

3. Consider this simplified RSA encryption example:
public_key = (e=3, n=33)
private_key = (d=7, n=33)
message = 4
encrypted = (message^e) mod n
decrypted = (encrypted^d) mod n
What is the decrypted message?

medium

A. 4

B. 7

C. 3

D. 9

Solution

1. Step 1: Calculate encrypted message

   encrypted = (4^3) mod 33 = 64 mod 33 = 31

2. Step 2: Calculate decrypted message

   decrypted = (31^7) mod 33. Calculating 31^7 mod 33 gives 4 (using modular exponentiation).

3. Final Answer:

   4 -> Option A

4. Quick Check:

   Decrypted message matches original message [OK]

Hint: Encrypt then decrypt returns original message [OK]

Common Mistakes:

• Forgetting to apply modulo operation
• Mixing up public and private keys
• Incorrectly calculating powers
• Assuming encrypted equals decrypted

4. A developer wrote this ECC key generation snippet but it fails:
private_key = generate_ecc_key()
public_key = private_key * G
What is the likely error?

medium

A. Public key is generated by multiplying G by private key, not the other way

B. Private key must be a point, not a number

C. Private key cannot be used to generate public key

D. Multiplying private key by G is incorrect; should add G

Solution

1. Step 1: Understand ECC key generation

   In ECC, the public key is generated by multiplying the base point G by the private key scalar.

2. Step 2: Identify the error in code

   The code multiplies private_key by G, but the correct order is G multiplied by private_key.

3. Final Answer:

   Public key is generated by multiplying G by private key, not the other way -> Option A

4. Quick Check:

   ECC public key = G * private key [OK]

Hint: Order matters: base point times private key [OK]

Common Mistakes:

• Reversing multiplication order
• Confusing addition with multiplication
• Thinking private key is a point
• Believing private key can't generate public key

5. Why might ECC be preferred over RSA for securing mobile devices?

hard

A. RSA is faster and more efficient on mobile devices

B. ECC uses smaller keys for similar security, saving battery and space

C. ECC keys are easier to guess than RSA keys

D. ECC does not require a private key

Solution

1. Step 1: Compare key sizes and efficiency

   ECC achieves strong security with smaller keys compared to RSA, which helps reduce processing power and battery use on mobiles.

2. Step 2: Evaluate other options

   ECC keys are not easier to guess; RSA is generally slower on mobiles; ECC requires private keys like RSA.

3. Final Answer:

   ECC uses smaller keys for similar security, saving battery and space -> Option B

4. Quick Check:

   ECC = smaller keys, better for mobiles [OK]

Hint: Smaller keys mean less power use on mobiles [OK]

Common Mistakes:

• Thinking ECC keys are weaker
• Assuming RSA is faster on mobiles
• Believing ECC doesn't use private keys
• Ignoring battery and space constraints