R1. What are the differences between message confidentiality and message integri

Question

R1. What are the differences between message confidentiality and message integrity? Can you have confidentiality without integrity? Can you have integrity without confidentiality? Justify your answer.

.    R3. From a service perspective, what is an important difference between a symmetric-key system and a public-key system?

.    R12. What does it mean for a signed document to be verifiable and non-forgeable?

.    R14. Suppose certifier.com creates a certificate for foo.com. Typically, the entire certificate would be encrypted with certifier.com’s public key. True or False?

.    R23. Suppose Bob initiates a TCP connection to Trudy who is pretending to be Alice. During the handshake, Trudy sends Bob Alice’s certificate. In what step of the SSL handshake algorithm will Bob discover that he is not commu- nicating with Alice?

Explanation / Answer

R1------>

Sending a message confidentially does not guarantee data integrity. Even when two nodes have authenticated each other, the integrity of a message could be compromised during the transmission of a message.

Yes, you can have integrity of a message without confidentiality. One can take a hash or sum of the message on both sides to compare. Often we share downloadable files and provide data integrity using md5 hash sums.

R3--------->

In public key systems, the encryption and decryption keys are distinct. The encryption key is known by the entire world (including the sender), but the decryption key is known only by the receiver.

R12----->

Meaning for a signed document to be verifiable and non-forgeable------>

R14 ----->

Suppose certifier.com creates a certificate for foo.com. Typically, the entire certificate would be encrypted with certifier.com’s public key.

False.

Hint :-

R23 ----->

Suppose Bob initiates a TCP connection to Trudy who is pretending to be Alice.

During the handshake, Trudy sends Bob Alice’s certificate.

Bob will acknowledge Trudy’s packets; Alice will see the acknowledgements for data that she never sent; Alice will send new acknowledgements, corresponding to the bytes she actually sent; Bob will receive two sets of inconsistent acknowledgments (from Alice and Trudy) and drop the connection

message confidentiality message integrity 1 Two or more hosts communicate securely, typically using encryption. The message transported has not been tampered with or altered. 2 The communication cannot be monitored (sniffed) by untrusted hosts. The communication between trusted parties is confidential. A message has integrity when the payload sent is the same as the payload received. 3 Message is being sent is only known by the sender and the reciever. Message intergrity keeps the sender and reciever exactly who they say they are.

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