Cryptographic Hash Functions and Applications(HMAC)

  1. Which criterion ensures that we can't find two messages that hash to the same digest?
    (a) One-wayness
    (b) Weak-collision-resistance
    (c) Strong-collision-resistance
    (d) None

  2. Which criterion Ensures that it must be extremely difficult or impossible to create the message if the message digest is given.
    (a) One-wayness
    (b) Weak-collision-resistance
    (c) Strong-collision resistance
    (d) None

  3. Consider the function h: {0,1}8 -> {0,1}4. Suppose h(x) = x xmod 5 mod 16, x in [0, 255]. The collision in h occurs for.
    (a) (1, 17)
    (b) (2, 16)
    (c) (1, 16)
    (d) (2, 17)

  4. The Merkle-Damgard Transform is mainly useful for
    (a) Converting any fixed-length collision resistant hash function to an arbitrary length collision resistant hash function
    (b) Converting arbitrary length hash function to a fixed length hash function
    (c) Constructing hash function from random function
    (d) None

  5. Understand HMAC scheme and find a break it using availble source code

  6. Understand Merkel-Damgard transform and Explain,how we are using it for HMAC?

  7. Understand and explain analogy between SHA1 and our dummy HMAC function

  8. Explain why HMAC is secure and on what assumptions this security is based?