Computer Science

Suppose that we have a block cipher and want to use it as a hash function. Let X be a specified constant and let M be a message consisting of a single block, where the block size is the size of the key in the block cipher. Define the hash of M as Y = E(X, M). Note that M is being used in place of the key in the block cipher.

a. Assuming that the underlying block cipher is secure, show that this hash function satisfies the collision resistance and one-way properties of a cryptographic hash function.

Don't use plagiarized sources. Get Your Custom Essay on
Computer Science
Just from $13/Page
Order Essay

b. Extend the definition of this hash so that messages of any length can be hashed. Does your hash function satisfy all of the properties of a cryptographic hash?

c. Why must a block cipher used as a cryptographic hash be resistant to a “chosen key” attack? Hint: If not, given plaintext P, we can find two keys K0 and K1 such that E(P,K0) = E(P,K1). Show that such a block cipher is insecure when used as a hash function.

We discussed the idea behind a forward search attack on a public key cryptosystems. In certain applications, a forward search attack can be used against a hash function.

a. What is a forward search attack on public key encryption, and how is it prevented?

b. Describe one plausible use for a hash function where a forward search attack is feasible.

c. How can you prevent a forward search attack on a hash function?

Place Order
Grab A 14% Discount on This Paper
Pages (550 words)
Approximate price: -
Paper format
  • 275 words per page
  • 12 pt Arial/Times New Roman
  • Double line spacing
  • Any citation style (APA, MLA, Chicago/Turabian, Harvard)

Try it now!

Grab A 14% Discount on This Paper

Total price:
$0.00

How it works?

Follow these simple steps to get your paper done

Place your order

Fill in the order form and provide all details of your assignment.

Proceed with the payment

Choose the payment system that suits you most.

Receive the final file

Once your paper is ready, we will email it to you.