Which of the following encryption schemes does a ciphertext leak nothing about the key that was used?

Assume the Diffie-Hellman protocol is run by two parties in the subgroup of Z23∗ generated by 2. (This subgroup has order 11.) If the first party chooses private exponent 3 and the second chooses private exponent 10, which of the following characterizes the execution of the protocol in this case?

Let H1, H2 be collision-resistant hash functions. Which of the following functions  H3 is NOT necessarily collision-resistant?

True or false: CBC-mode encryption with PKCS #7 padding provides message integrity, as long as the receiver makes sure to verify the padding upon decryption.

Assume CBC-mode encryption using an 8-byte (64-bit) block cipher. Say a sender encrypts the 8-byte message “sendme$2” (encoded in ASCII), resulting in ciphertext 0xFF 09 28 30 8C 93 81 06 39 D0 81 5A 07 79 17 43. Which of the following ciphertexts will decrypt to the message “sendme$4” ?

Assume a sender and receiver use the encrypt-and-authenticate approach for variable-length messages, using CTR-mode encryption and a variant of CBC-MAC secure for authenticating variable-length data (and independent keys for each). Which of the following statements is true?

? Alternatively, what is the remainder when 128 raised to 128 is divided by 7?

Define the generator G by G(x) = x | x. (G maps inputs of length n to outputs of length 2n). Which of the following algorithms A distinguishes the output of G from uniform?

Which of the following BEST describes the security offered by the Diffie-Hellman key-exchange protocol (assuming the DDH problem is hard)?

Which of the following is a drawback of the private-key setting that is NOT addressed by the public-key setting?