Câu hỏi phỏng vấn Cryptography
Câu hỏi

What is a key?

Câu trả lời

In cryptography, a key is a piece of information that determines the output of a cryptographic algorithm. It is a variable value that is applied using an algorithm to a string or block of unencrypted text to produce encrypted text, known as ciphertext. The key is essential for both the encryption and decryption processes, ensuring that data remains secure and accessible only to authorized parties.

Types of Cryptographic Keys

  1. Symmetric Keys:

    • Definition: Symmetric key cryptography, also known as secret key cryptography, uses a single key for both encryption and decryption.
    • Usage: The same key is shared between the sender and the recipient. This key must be kept secret to ensure the security of the communication.
    • Example: If a message is encrypted with a symmetric key, the same key must be used to decrypt it[2][3][8].
  2. Asymmetric Keys:

    • Definition: Asymmetric key cryptography, also known as public key cryptography, uses a pair of keys: a public key and a private key.
    • Usage: The public key is used for encryption and can be shared openly, while the private key is used for decryption and must be kept secret. This method ensures that even if the public key is intercepted, the encrypted message cannot be decrypted without the private key.
    • Example: A message encrypted with a public key can only be decrypted by the corresponding private key, ensuring secure communication even over insecure channels[2][4][5].

Functions of Cryptographic Keys

  • Encryption and Decryption: Keys are used to transform plaintext into ciphertext (encryption) and back into plaintext (decryption). This ensures that data remains confidential and is only accessible to those with the correct key[1][3].
  • Authentication: Keys can verify the identity of an entity, ens...


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