Cryptography Basics Quiz

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Questions and Answers

What does the Initialization Vector (IV) do in CBC mode?

It ensures proper encryption without previous output. (correct)

It increases the key size for stronger encryption.

It encrypts the plaintext directly.

It reduces the number of encryption rounds.

The final round of AES encryption includes the MixColumns step.

False

What are the key sizes used in the Advanced Encryption Standard (AES)?

128, 192, or 256

Public key encryption involves a _ key, which is kept secret, and a _ key, which is shared.

private, public Signup and view all the answers

Match the encryption methods with their descriptions:

Initialization Vector (IV) = Ensures proper encryption without previous output Public Key Encryption = Solves key distribution problems using a key pair Digital Signatures = Provides integrity and authentication for messages AES = Uses substitution and permutation for encryption Signup and view all the answers

Which step in AES involves permutations to mix the columns of data?

MixColumns Signup and view all the answers

Digital signatures use a public key to sign a message and a private key to verify it.

False Signup and view all the answers

What problem does public key cryptography address?

Key distribution problem Signup and view all the answers

What does the Caesar Cipher do to each letter in the alphabet?

It shifts each letter forward by three letters. Signup and view all the answers

The Vigenère Cipher uses only one letter to create the ciphertext.

False Signup and view all the answers

What is the purpose of Padding in cryptography?

To adjust the length of the message to fit the block size required for encryption. Signup and view all the answers

In encryption, the process of obscuring the relationship between the key and the ciphertext is known as _______.

confusion Signup and view all the answers

Match the following terms with their descriptions:

S-boxes = Substitute data blocks using a lookup table P-boxes = Permute bits to change their order Key schedules = Generate multiple round keys from an initial key Modes of Operation = Define how block ciphers process data Signup and view all the answers

Which mode of operation links blocks using an XOR operation on the output of the previous block?

Cipher Block Chaining (CBC) Signup and view all the answers

In the Electronic Codebook (ECB) mode, each block of plaintext is encrypted independently.

True Signup and view all the answers

What is the primary function of stream ciphers?

To perform encryption and decryption on a continuous stream of data. Signup and view all the answers

Study Notes

Caesar Cipher

Each letter is shifted three places down the alphabet (e.g., A becomes D, F becomes I).

Vigenère Cipher

Takes plaintext and a keyword to create ciphertext.
The plaintext letter is the row key, and the keyword letter is the column key.
The corresponding letter is the cipher letter.

Stream Ciphers

Encryption and decryption are performed on a stream of data (e.g., bitwise XOR with a key).

Padding

A cryptographic message syntax (CMS) from RFC 5656.
Pads the trailing end with a value equal to k - (i mod k) octets.
- Example: 8-byte key, 12-byte message = 4 padding bytes of value 4.
S-boxes substitute data blocks using a lookup table. This obscures the relationship between the key and the ciphertext. Each ciphertext bit relies on multiple key parts.
P-boxes permute bits (rearrange, repeat, or discard).

Key Schedules

Generate multiple round keys from the initial key.
Enhances the complexity of the encryption process.
Each round uses different subkeys, making it difficult to relate plaintext to ciphertext.

Modes of Operation

Electronic Codebook (ECB): Encrypts each block individually (less secure).
Cipher Block Chaining (CBC): Links blocks using XOR, improving security. Uses an Initialization Vector (IV).

Advanced Encryption Standard (AES)

Modern symmetric encryption.
Uses substitution and permutation network.
128, 192, or 256 bit key sizes.
10, 12, or 14 rounds.
Data is structured as matrices (tables).
Steps within each round:
- SubBytes: Performs substitutions.
- ShiftRows: Shifts rows.
- MixColumns: Mixes columns.
- AddRoundKey: XORs with round key.
The final round does not include MixColumns.

Public Key Cryptography

Solves key distribution problems.
Uses a key pair:
- Private key (secret).
- Public key (shared).
Encrypts with public key and decrypts with private key.
Provides confidentiality (encrypt with recipient's public key) and authenticity (encrypt with sender's private key).
Layered encryption can ensure both confidentiality and authenticity.

Digital Signatures

Provides integrity and authentication for messages.
Uses a private key to sign a message, and a public key to verify it.
Ensures the message wasn't altered and is from the claimed sender.
Hash functions manage varying message sizes.
Collision resistance prevents similar messages from producing identical hashes.

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Description

Test your knowledge on essential cryptographic techniques such as Caesar Cipher, Vigenère Cipher, and Stream Ciphers. This quiz covers the principles of padding and key schedules to enhance encryption complexity. Dive into the fundamental concepts of cryptography and understand how they are applied for secure data transmission.

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