Practise Protecting digital systems and data (incl. encryption). 19 exam-style questions plus unlimited generated ones on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
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State the term used for data after it has been encrypted.
Ciphertext
Give the ciphertext produced when the word CODE is encrypted using a Caesar cipher with a shift of 2 to the right.
EQFG
A message was encrypted using a Caesar cipher with a shift of 5 to the right. Spaces were not changed. Convert the ciphertext RJJY FY YMWJJ back into plaintext.
MEET AT THREE
This Python function encrypts a message using a Caesar cipher. The message contains only capital letters and spaces. The ASCII code for 'A' is 65.
01 def encrypt(message, key):
02 result = ""
03 for letter in message:
04 if letter == " ":
05 result = result + " "
06 else:
07 position = ord(letter) - 65
08 position = (position + key) % 26
09 result = result + chr(position + 65)
10 return result
State the value returned by encrypt("ZOO", 3).
CRR
Give two methods of protecting a computer system from malware.
Up-to-date anti-malware software and prompt installation of security updates.
State why software updates (patches) should be installed as soon as possible.
They fix known vulnerabilities before attackers can exploit them.
Sample questions
Written for this site in the style of Edexcel exam questions. They are not taken from real past papers.
Question 1Easy3 marks
(a) Define the term 'encryption'.[1]
(b) State the term used for data after it has been encrypted.[1]
(c) State what is needed, as well as the encryption algorithm, to decrypt the data.[1]
Show the answer and mark scheme
(a)Answer: Scrambling data using an algorithm and a key so that it cannot be understood without the key.
converting data (plaintext) into a form (ciphertext) that cannot be understood without the key
(b)Answer: Ciphertext
ciphertext
(c)Answer: The key.
the key / the (decryption) key
Question 2Medium4 marks
(a) Explain why data should be encrypted before it is sent over the internet.[2]
(b) Explain why the data on a laptop's storage drive should be encrypted.[2]
Show the answer and mark scheme
(a)Answer: It may be intercepted, but without the key the ciphertext is meaningless.
data sent over the internet could be intercepted (e.g. by a hacker)
encrypted data cannot be understood without the key, so an interceptor cannot use it
(b)Answer: If the laptop is lost or stolen, the finder cannot read the data without the key.
laptops are easily lost or stolen
so anyone who finds or steals it cannot read the data without the key / password
Question 3Hard4 marks
This Python function encrypts a message using a Caesar cipher. The message contains only capital letters and spaces. The ASCII code for 'A' is 65.
01 def encrypt(message, key):
02 result = ""
03 for letter in message:
04 if letter == " ":
05 result = result + " "
06 else:
07 position = ord(letter) - 65
08 position = (position + key) % 26
09 result = result + chr(position + 65)
10 return result
(a) State the value returned by encrypt("ZOO", 3).[1]
(b) Explain the purpose of % 26 in line 08.[2]
(c) State why line 07 subtracts 65.[1]
Show the answer and mark scheme
(a)Answer: CRR
CRR
(b)Answer: It keeps the position between 0 and 25, so shifts past Z wrap round to A, B, C…
it gives the remainder after dividing by 26, so the position stays in the range 0 to 25
so letters that are shifted past Z wrap around to the start of the alphabet (e.g. Z with a key of 3 becomes C)
(c)Answer: It converts the letter's ASCII code (65–90) into an alphabet position (0–25).
to turn the ASCII code of a capital letter (65 to 90) into its position in the alphabet (0 to 25)