Invitation to Computer Science 8th Edition

Published by Cengage Learning
ISBN 10: 1337561916
ISBN 13: 978-1-33756-191-4

Chapter 8 - 8.3 - Encryption - Practice Problems - Page 412: 3a

Answer

\begin{array}{l} {\text { Step } 1 . \text { Apply the S mapping to }(M\ Q) \text { to get }(13\ 17) .} \\ {\text { Step } 2 . \text { Multiply result times } M :(13\ 17) \times\left[\begin{array}{cc}{3} & {5} \\ {2} & {3}\end{array}\right]} \\ {\qquad=(13 \times 3+17 \times 2\ \ \ \ \ 13 \times 5+17 \times 3)=(73 \ \ 116) \rightarrow(21\ \ 12)} \\ \\ {\text { Step } 3 . \text { Apply $S^{\prime}$ to $(21\ 12)$ to get $(U\ L)$} } \end{array}

Work Step by Step

\begin{array}{l} {\text { Step } 1 . \text { Apply the S mapping to }(M\ Q) \text { to get }(13\ 17) .} \\ {\text { Step } 2 . \text { Multiply result times } M :(13\ 17) \times\left[\begin{array}{cc}{3} & {5} \\ {2} & {3}\end{array}\right]} \\ {\qquad=(13 \times 3+17 \times 2\ \ \ \ \ 13 \times 5+17 \times 3)=(73 \ \ 116) \rightarrow(21\ \ 12)} \\ \\ {\text { Step } 3 . \text { Apply $S^{\prime}$ to $(21\ 12)$ to get $(U\ L)$} } \end{array}
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