Please show your work in detail (no credit is given for a final answer). Please provide responses directly under each question.
- Describe cipher-block chaining (CBC) mode of operation of symmetric block ciphers. Why is it possible in CBC mode to perform decryption in parallel on multiple blocks of plaintext, but not encryption?
- What is the ciphertext of the word cybersecurity using the rail fence cipher (key=2), followed by the ROT13 cipher, followed by the Caesar cipher?
- Perform encryption and decryption using the RSA algorithm given the following: p=47; q=59, e=17; M=11.
- What is the plaintext if C=10, e=5, and n=35 in a public-key system using RSA?
- Describe the components of a PKI. Search the Internet for a security incident which occurred because of a failure in one of the phases of the public-key certificate lifecycle. Explain how the incident could have been prevented.
- Which features of the TLS protocol prevent replay, IP spoofing, and MITM attacks? Explain.
- How can User A forge User B’s signature on an arbitrary message if User B uses the same RSA digital signature key pairs and RSA encryption key pairs? (Hint: User B’s help is needed.)
- Why is it important that the hash functions used in RSA digital signatures have collision and preimage resistance?
- Explain which security properties of a hash function are useful in detection of computer viruses, storing a passphrase, and HMAC.
- Explain why public-key cryptosystems have longer key lengths than symmetric cryptosystems.
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