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Questions and Answers
What does the Initialization Vector (IV) do in CBC mode?
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.
The final round of AES encryption includes the MixColumns step.
False (B)
What are the key sizes used in the Advanced Encryption Standard (AES)?
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.
Public key encryption involves a _____ key, which is kept secret, and a _____ key, which is shared.
Match the encryption methods with their descriptions:
Match the encryption methods with their descriptions:
Which step in AES involves permutations to mix the columns of data?
Which step in AES involves permutations to mix the columns of data?
Digital signatures use a public key to sign a message and a private key to verify it.
Digital signatures use a public key to sign a message and a private key to verify it.
What problem does public key cryptography address?
What problem does public key cryptography address?
What does the Caesar Cipher do to each letter in the alphabet?
What does the Caesar Cipher do to each letter in the alphabet?
The Vigenère Cipher uses only one letter to create the ciphertext.
The Vigenère Cipher uses only one letter to create the ciphertext.
What is the purpose of Padding in cryptography?
What is the purpose of Padding in cryptography?
In encryption, the process of obscuring the relationship between the key and the ciphertext is known as _______.
In encryption, the process of obscuring the relationship between the key and the ciphertext is known as _______.
Match the following terms with their descriptions:
Match the following terms with their descriptions:
Which mode of operation links blocks using an XOR operation on the output of the previous block?
Which mode of operation links blocks using an XOR operation on the output of the previous block?
In the Electronic Codebook (ECB) mode, each block of plaintext is encrypted independently.
In the Electronic Codebook (ECB) mode, each block of plaintext is encrypted independently.
What is the primary function of stream ciphers?
What is the primary function of stream ciphers?
Flashcards
Caesar Cipher
Caesar Cipher
A simple substitution cipher where each letter is shifted a fixed number of positions down the alphabet.
Vigenère Cipher
Vigenère Cipher
A method of encrypting alphabetic text using a keyword to create different substitution rules for each letter.
Stream Ciphers
Stream Ciphers
Encrypting and decrypting data one bit or byte at a time using a key.
Padding
Padding
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S-boxes
S-boxes
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P-boxes
P-boxes
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Key schedules
Key schedules
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Modes of Operation
Modes of Operation
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ECB (Electronic Codebook)
ECB (Electronic Codebook)
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CBC (Cipher Block Chaining)
CBC (Cipher Block Chaining)
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Initialization Vector (IV)
Initialization Vector (IV)
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Advanced Encryption Standard (AES)
Advanced Encryption Standard (AES)
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Symmetric Encryption
Symmetric Encryption
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Key Distribution Problem
Key Distribution Problem
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Public Key Cryptography
Public Key Cryptography
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Public Key
Public Key
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Private Key
Private Key
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Digital Signatures
Digital Signatures
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Hash Function
Hash Function
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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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