Encrypting a message by crypto device

Assignment Help Basic Computer Science

Reference no: EM1346010

Q1) A foreign navy has implemented a secure communications system in which submarine commanders transmit a single 5-letter message every day. Messages may only use capital (English) letters, and all messages are equally probable. Crypto device encrypts every message into 20 bits of ciphertext.

a. What is the entropy of the plaintext message?

b. What is the entropy of the ciphertext message?

c. Is this a good cryptosystem? Why or why not?

Suppose that Eve runs a key server. Alice downloads a key from the key server which Eve claims is Bob's public key. Bob downloads a key from the key server which Eve claims is Alice's public key.

a. Given that Alice and Bob both assume that they have the correct public keys for the other party, and assuming that Eve can intercept any messages passed between Alice and Bob, is there any way that Eve can read the encrypted communications between the two parties? If so, how could she do it, and would Bob or Alice know that Eve was reading their messages?

b. What steps could Alice take to ensure that the public key which Eve claims belongs to Bob is actually correct?

Reference no: EM1346010

Questions Cloud

Improve communication in organizations : Explain a time when you were trying to communicate with another person and active listening would have been helpful.

Assume an angle of 30 degrees with the vertical : A hot ( ) lump of metal has a mass of 250g and a specific heat of 0.25 . John drops the metal into a 500g calorimeter containing 75g of water at . The calorimeter is constructed of a material that has a specific heat of 0.10 . When equilibrium is ..

Quality of business environment in host country : How can government policies impact the quality of the business environment in the host country? You are a foreign investor. What are your main concerns regarding the investment opportunities?

Buying and selling of contracts : Assume you desire to hedge a $400 million bond portfolio with duration of 4.3% using ten year Treasury note futures with a duration of 6.7%,

Encrypting a message by crypto device : Crypto device encrypts every message into 20 bits of ciphertext.

Define and show formal and informal communication networks : Define and show formal and informal communication networks as well as the three important functions of formal communication networks.

Question on financial markets : What are the bid-ask spreads for each currency India and Brazil (include calculations) What are the implications of the presence or absence of a forward exchange market?

Compute the equilibrium price and quantity in this market : illustrate what is the new equilibrium price and quantity. Compute the equilibrium price and quantity in this market.

Describe why you believe barrier is challenging : Describe why you believe this barrier is challenging for organizations as well as what you would do to overcome it, if you were faced with change in your organization.

User Account

All Pages