Encryption basics in Intro to Computing - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

What is the main purpose of encryption?

Encryption is a process used in computing and communication. What is its main purpose?

A To delete data permanently from a device

B To convert readable data into a secret code to protect it from unauthorized access

C To compress data so it takes less space on the disk

D To speed up the transmission of data over the internet

💡 Hint

Think about why secret messages are used in spy movies.

Encryption changes readable information into a coded form so only authorized people can read it. This protects privacy and security.

❓ trace

intermediate

Trace the output of a simple Caesar cipher

Given the text 'HELLO' and a Caesar cipher that shifts letters by 3 places forward, what is the encrypted output?

Intro to Computing

def caesar_encrypt(text, shift):
    result = ''
    for char in text:
        if char.isalpha():
            shifted = chr((ord(char) - 65 + shift) % 26 + 65)
            result += shifted
        else:
            result += char
    return result

print(caesar_encrypt('HELLO', 3))

A IFMMP

B EBIIL

C HELLO

D KHOOR

💡 Hint

Each letter moves 3 places forward in the alphabet. 'H' becomes 'K'.

The Caesar cipher shifts each letter by the given number. 'H' + 3 = 'K', 'E' + 3 = 'H', and so on, resulting in 'KHOOR'.

❓ identification

advanced

Identify the type of encryption used

Which type of encryption uses the same key for both encrypting and decrypting data?

A Steganography

B Asymmetric encryption

C Symmetric encryption

D Hashing

💡 Hint

Think about a single key that locks and unlocks a door.

Symmetric encryption uses one key for both encrypting and decrypting. Asymmetric uses two keys (public and private).

❓ Comparison

advanced

Compare encryption and hashing

Which statement correctly compares encryption and hashing?

A Encryption is reversible with a key; hashing is one-way and not reversible

B Both encryption and hashing are reversible processes

C Hashing requires a key to reverse; encryption does not

D Encryption and hashing both produce the same output for the same input

💡 Hint

Think about whether you can get the original message back.

Encryption can be reversed using a key to get original data. Hashing creates a fixed output that cannot be reversed.

🚀 Application

expert

Determine the output length of encrypted data

A message of 128 bytes is encrypted using AES with a block size of 16 bytes. What is the length of the encrypted output in bytes?

A 128 bytes

B 144 bytes

C 256 bytes

D 16 bytes

💡 Hint

AES encrypts data in fixed-size blocks. If input fits exactly, output size matches input size.

AES uses 16-byte blocks. 128 bytes is exactly 8 blocks (128/16). No padding needed, so output is 128 bytes.