QUESTION

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Alice wants to send a single bit of information (a yes or no) to Bob by means of a word of length 2. Alice and Bob have 4 possible keys available to perform message authentication. The following matrix shows the 2-bit word sent for each message under each key: \begin{tabular}{|r|c|c|} \hline & Message & \\ \hline Key & 0 & 1 \\ \hline 1 & 00 & 01 \\ \hline 2 & 10 & 00 \\ \hline 3 & 01 & 11 \\ \hline 4 & 11 & 10 \\ \hline \end{tabular} A. What is the probability that someone else can successfully impersonate Alice? B. What is the probability that someone can replace an intercepted message with another message successfully?

Public Answer

4E6O4F The First Answerer