Fig. 1 shows a grid used by a youth orchestra to conceal seat codes on printed tickets. The grid maps plaintext letters to ciphertext letters with a shift o...
Question 1 Report
Fig. 1 shows a grid used by a youth orchestra to conceal seat codes on printed tickets. The grid maps plaintext letters to ciphertext letters with a shift of 1. Table 1 shows ticket data for three performances, including the number of seats and the encrypted code length. A volunteer has written an algorithm to check whether every output word has the same number of letters as its input word.
Fig. 1: ticket cipher grid
| Performance | Seats sold | Plaintext code letters | Ciphertext code letters |
|---|---|---|---|
| Friday | 86 | 3 | 3 |
| Saturday | 100 | 4 | 4 |
| Sunday | 73 | 5 | 5 |
Table 1: ticket program data
(a) Identify the ciphertext letter for plaintext Z. [1]
(b) State the Caesar shift used by the grid. [1]
(c) Identify the performance with 100 seats sold. [1]
(d) Give one reason why the number of letters does not change after this encryption. [1]
(e) Complete: plaintext WAX becomes ciphertext ______. [2]
Answer Details
(a) Plaintext Z maps to ciphertext A [1]. This is the wrap-around point of a shift cipher.
(b) The Caesar shift is 1 [1].
(c) The performance with 100 seats sold is Saturday [1].
(d) The number of letters does not change because each plaintext letter is replaced by exactly one ciphertext letter [1].
(e) W becomes X [1], A becomes B [1], and X becomes Y. Therefore WAX becomes XBY [2].
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