ACARA Digital Technologies Years 9–10 Word Scramble: Cyber Security Threats and Vulnerabilities (Modules 860–875)
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Word scramble
Unscramble the letters and write each key term on the line.
1
EYURCFNQE YNLISSAA
Counting how often each letter appears in ciphertext and matching the most common ones to common English letters like E, to work out a substitution cipher's key.
2
NTIPRNIOAOTSS PCRIEH
A cipher that keeps the same letters but changes their order, like writing a message in a zigzag across rails and then reading each rail in turn.
3
=EDCO("A")
Gives the number code of a letter, so ______ returns 65. Its partner =CHAR(65) turns a code back into a letter. Capital letters start at 65 (A) and run to 90 (Z).
4
=DNU(EMMROB, IRSIVOD)
Returns the remainder after division, so numbers wrap around. =MOD(27,26) gives 1, which is how a Caesar shift loops from Z back to A.
5
=E3M5(O26(O2BH(6D)-DC-6,RA)+5C)
Shifts a letter back by the key (3) to decrypt it. Subtracting the key undoes adding it, and MOD 26 wraps A-Z around so the result stays a letter.
6
DRO() NDA RHC()
ord("A") returns the number code of a character (65). chr(65) turns a number code back into its character ("A"). Ciphers use them to change letters to numbers and back.
7
AH.PISCHAL()
Returns True if the character ch is a letter, so a Caesar loop can shift letters and leave spaces and punctuation unchanged. ch.isupper() checks for capitals.
8
HRC((OHR(CD) - 56 + HFSIT) % 62 + 56)
Shifts an upper-case letter ch along the alphabet by shift, wrapping past Z back to A. A for loop applies it to each letter and builds the ciphertext with +=, skipping spaces.
9
AEICHA(PRECRS, -HISTF)
Decrypts by calling the same Caesar function with the negative of the original shift. Shifting back by the same amount undoes the encryption, and % keeps the letters wrapping.
Answer Key
ACARA Digital Technologies Years 9–10 · Modules 860–875
1EYURCFNQE YNLISSAA → frequency analysis — Counting how often each letter appears in ciphertext and matching the most common ones to common English letters like E, to work out a substitution cipher's key.
2NTIPRNIOAOTSS PCRIEH → transposition cipher — A cipher that keeps the same letters but changes their order, like writing a message in a zigzag across rails and then reading each rail in turn.
3=EDCO("A") → =CODE("A") — Gives the number code of a letter, so =CODE("A") returns 65. Its partner =CHAR(65) turns a code back into a letter. Capital letters start at 65 (A) and run to 90 (Z).
4=DNU(EMMROB, IRSIVOD) → =MOD(number, divisor) — Returns the remainder after division, so numbers wrap around. =MOD(27,26) gives 1, which is how a Caesar shift loops from Z back to A.
5=E3M5(O26(O2BH(6D)-DC-6,RA)+5C) → =CHAR(MOD(CODE(B2)-65-3,26)+65) — Shifts a letter back by the key (3) to decrypt it. Subtracting the key undoes adding it, and MOD 26 wraps A-Z around so the result stays a letter.
6DRO() NDA RHC() → ord() and chr() — ord("A") returns the number code of a character (65). chr(65) turns a number code back into its character ("A"). Ciphers use them to change letters to numbers and back.
7AH.PISCHAL() → ch.isalpha() — Returns True if the character ch is a letter, so a Caesar loop can shift letters and leave spaces and punctuation unchanged. ch.isupper() checks for capitals.
8HRC((OHR(CD) - 56 + HFSIT) % 62 + 56) → chr((ord(ch) - 65 + shift) % 26 + 65) — Shifts an upper-case letter ch along the alphabet by shift, wrapping past Z back to A. A for loop applies it to each letter and builds the ciphertext with +=, skipping spaces.
9AEICHA(PRECRS, -HISTF) → caesar(cipher, -shift) — Decrypts by calling the same Caesar function with the negative of the original shift. Shifting back by the same amount undoes the encryption, and % keeps the letters wrapping.