Introduction to Cryptography (with correct solutions)

1. How did the ATBASH cipher work? correct answers By substituting each letter for the letter from the opposite end of the alphabet (i.e. Abecomes Z, B becomes Y, etc.) 2. DES has a key space of what? correct answers 2^56 3. Which of the following are valid key sizes for AES (choose three)? correct answers c. 128 d. 192 e. 256 4. Which of the following algorithms uses three different keys to encrypt the plain text? correct answers 3DES Triple Data Encryption System 5. Which of the following is a block cipher? correct answers AES The Advanced Encryption Standard (AES) is a symmetric-key block cipher algorithm and U.S. government standard for secure and classified data encryption and decryption. 6. Which of the following is a type of encryption that has two different keys. One key can encrypt the message and the other key can only decrypt it? correct answers Asymmetric 7. Which of the following is an asymmetric cipher? correct answers RSA The acronym stands for Rivest, Shamir, and Adelman, the inventors of the technique. The RSA algorithm is based on the fact that there is *no efficient way to factor very large numbers.* 8. A cipher is defined as what correct answers The algorithm(s) needed to encrypt and decrypt a message 9. Which of the following is not an asymmetric system? correct answers AES The Advanced Encryption Standard (AES) is a symmetric-key block cipher algorithm and U.S. government standard for secure and classified data encryption and decryption. 10. John is going to use RSA to encrypt a message to Joan. What *key* should he use? correct answers Joan's public key 11. What advantage do symmetric algorithms have over asymmetric algorithms correct answers Symmetric algorithms are faster than Asymmetric algorithms