Cryptography Basics Quiz

The average amount of information contained in a message from a specific class, measured in bits.

A symmetric encryption scheme where a key of the same length as the plaintext is used to encrypt the message and cannot be reused.

A symmetric encryption algorithm that encrypts individual plaintext symbols (bits) with a keystream, one at a time.

A symmetric encryption algorithm that processes plaintext in fixed-size blocks, using a key to encrypt each block.

A symmetric encryption scheme where the same key is used for both encryption and decryption, operating on fixed-size blocks of data.

A fundamental building block in cryptography that transforms plaintext into an unreadable ciphertext.

The process of converting ciphertext back into its original plaintext form.

A cryptographic technique that uses the same secret key to both encrypt and decrypt data.

A cryptographic method that utilizes two related keys: a public key for encryption and a private key for decryption.

Also known as a 'secret key' cryptography, this technique uses a single key for both encryption and decryption.

Also known as 'public key' cryptography, this system employs a pair of keys, one public and one private, for encryption and decryption, respectively.

A function that provides a short, fixed-length string called a message authentication code (MAC), which is used to verify the authenticity and integrity of a message.

A cryptographic mechanism that combines encryption and authentication, ensuring both confidentiality and integrity of data.

A technique used to ensure that the length of the plaintext is a multiple of the block size used by the block cipher.

A block cipher that encrypts data in 64-bit blocks. DES is a symmetric encryption algorithm, meaning that the same key is used for both encryption and decryption.

Adding extra bytes to a plaintext message to make its length a multiple of the block size. This is necessary because DES can only process data in full 64-bit blocks.

The process of converting plaintext data into ciphertext using a specific algorithm and key. This makes the data unreadable without the correct decryption key.

The process of converting ciphertext back into the original plaintext data using the corresponding key. This reverses the encryption process and makes the data readable again.

The original, unencrypted data that is to be protected. It is the input for the encryption process.

Each plaintext block is XORed with the previous ciphertext block before encryption. This means changing one bit in the plaintext affects the encryption of all subsequent blocks.

Decrypting a ciphertext block with an error only affects the corresponding plaintext block and the next. Subsequent blocks remain unchanged.

The process of ensuring that data is accessible only to authorized individuals.

The process of ensuring that data has not been tampered with and that it originates from a trusted source.

A unique value used to initialize the first encryption block in CBC mode. It is XORed with the first plaintext block to generate the first ciphertext.

A block cipher mode that encrypts data by XORing each plaintext block with the previous ciphertext block, then encrypting the result.

Plaintext is the original, unencrypted data.

Ciphertext is the encrypted data that is unreadable without the proper decryption key.

A padding scheme used in CrypTool DES(ECB) mode where zeros are added to the end of the plaintext to make its length a multiple of the block size.

The Java cryptography package that offers different encryption and decryption algorithms, including DES with different padding schemes.

A padding scheme used in DES(ECB) mode where the padding is done according to the PKCS#5 standard. This scheme adds padding bytes to the plaintext to make its length a multiple of the block size.

A padding scheme used in DES(ECB) mode where no padding is added to the plaintext. This scheme requires the plaintext to be a multiple of the block size for encryption to succeed.

A block cipher mode in which the same plaintext block always produces the same ciphertext block. It is vulnerable to attacks as patterns in the plaintext are preserved in the ciphertext.

A block cipher mode that involves XORing the current plaintext block with the previous ciphertext block before encryption. Each plaintext block is encrypted differently, making it more secure than ECB mode.

In CBC mode, the same plaintext block is encrypted differently based on its position in the sequence because of the XOR operation with the preceding ciphertext block.

A MAC is calculated using a secret key shared between the sender and receiver, applied to the entire message. The MAC is then transmitted alongside the message itself.

Providing confidentiality means keeping a message secret, while integrity ensures the message was not altered during transmission. MACs provide integrity and authentication.

A MAC ensures that the message has not been altered in transit. This is because a different message would result in a different MAC, which would be detected by the receiver.

The MAC is calculated using the same secret key shared by both the sender and receiver, making it impossible for anyone else to create a valid MAC for the message.

By incorporating a sequence number within the message, a MAC can also ensure that the messages are received in the correct order, as altering the sequence number would change the MAC and be detected.

Symmetric encryption techniques like DES/AES with modes like ECB/CBC/CTR provide confidentiality, but don't guarantee integrity. A MAC is needed to ensure that the message hasn't been altered.

MACs are used in conjunction with symmetric encryption to provide both confidentiality and integrity, offering a complete security solution.