Introduction to Public-Key Cryptography Answers 1. What is a primary reason for the importance of key management in public-key cryptography? A. Key management reduces computational complexity. B. Secure handling and storage of private keys prevent unauthorized access. C. It simplifies the process of digital signatures. D. It allows for the rapid exchange of secret keys. Answer: Secure handling and storage of private keys prevent unauthorized access. (B) Secure handling and storage of private keys is crucial to prevent loss or compromise, which can lead to severe security breaches. 2. Which statement best describes the role of digital certificates in public-key cryptography? A. They are required for all secure transactions. B. They simplify the generation of public keys. C. They eliminate the need for key management. D. They verify the authenticity of public keys to prevent man-in-the-middle attacks. Answer: They verify the authenticity of public keys to prevent man-in-themiddle attacks. (D) Digital certificates provide mechanisms for verifying the authenticity of public keys, thus preventing potential man-in-the-middle attacks. 3. How does the size of keys in public-key cryptography affect security? A. Larger keys are less secure due to increased complexities. B. Key size has no significant impact on security. C. Larger keys generally provide greater security but with increased computational costs. D. Smaller keys require less computational power and are therefore more efficient. Answer: Larger keys generally provide greater security but with increased computational costs. (C) The size of the keys used directly impacts the security level; larger key sizes typically offer greater security at the expense of increased computational costs. 4. Why is the computational complexity important in public-key cryptography? A. It reduces the size of encrypted data. B. It helps maintain the security of public-key systems against evolving threats. C. It ensures faster processing of secure transactions. D. It eliminates the need for key validation. Answer: It helps maintain the security of public-key systems against evolving threats. (B) The security of public-key cryptography relies on the difficulty of solving specific mathematical problems, making regular evaluation necessary to maintain security. 5. What is a primary application of digital signatures in public-key cryptography? A. To verify the authenticity and integrity of documents. B. To encrypt sensitive emails. C. To authenticate identities in login systems. D. To manage encryption keys. Answer: To verify the authenticity and integrity of documents. (A) Digital signatures are used to verify the authenticity and integrity of documents, software, and other digital data, serving as a key application in public-key cryptography. 6. What is a key characteristic of public-key cryptography compared to symmetric-key cryptography? A. It uses only one key for both encryption and decryption. B. It limits the number of users able to decrypt messages. C. It requires less computational power. D. It allows secure communication without prior key exchange. Answer: It allows secure communication without prior key exchange. (D) Public-key cryptography allows secure communication without requiring prior secret key exchange. 7. What is the role of a public key in public-key cryptography? A. It is used for decrypting messages. B. It can be shared without compromising security. C. It is used for generating digital signatures. D. It must be kept secret by its owner. Answer: It can be shared without compromising security. (B) The public key can be shared freely without compromising security. 8. Which cryptographic process transforms data into an unreadable format? A. Signing B. Encryption C. Hashing D. Decryption Answer: Encryption (B) Encryption is the process of transforming data into an unreadable format to prevent unauthorized access. 9. What is the main purpose of a digital signature? A. To generate encryption keys. B. To verify the authenticity and integrity of a digital document. C. To replace public keys in transactions. D. To encrypt a message. Answer: To verify the authenticity and integrity of a digital document. (B) A digital signature is used to verify the authenticity and integrity of a digital document. 10. Which of the following algorithms is specifically designed for digital signatures? A. DSA B. AES C. Elliptic Curve Cryptography D. RSA Answer: DSA (A) DSA (Digital Signature Algorithm) is specifically designed for creating digital signatures. 11. What is the mathematical basis for the RSA algorithm? A. Elliptic curves B. Hash functions C. Prime factorization D. Matrix multiplication Answer: Prime factorization (C) RSA is based on the difficulty of factoring large numbers, which involves prime factorization. 12. Which of the following statements about Elliptic Curve Cryptography (ECC) is true? A. It provides similar security with smaller key sizes. B. It is primarily used for symmetric encryption. C. It requires larger key sizes compared to RSA for similar security. D. It is less efficient in resource-constrained environments. Answer: It provides similar security with smaller key sizes. (A) ECC offers similar security to RSA but with smaller key sizes, making it more efficient. 13. What makes the private key essential in a public-key cryptography system? A. It encrypts the messages for all users. B. It should be kept secret to maintain security. C. It verifies digital signatures for all documents. D. It generates the public key for other users. Answer: It should be kept secret to maintain security. (B) The private key must be kept secret by its owner to ensure the security of the cryptographic system.