2.3. Encryption
A subsection of Computer Science, 0478, through 2. Data transmission
Listing 8 of 8 questions
A simple symmetric encryption system is used to encrypt messages. Each letter of the alphabet is substituted by another letter. Plain text a b c d e f g h i j k l m n o p q r s t u v w x y z Cypher text v p n a q b r u z s c o y k w f x i e m d j t l h g Convert the following plain text to cypher text. Plain text: d a t a s e c u r i t y Cypher text: A new cypher text is created by shifting each letter of the alphabet five places to the right. Show the new cypher text below. Plain text a b c d e f g h i j k l m n o p q r s t u v w x y z New cypher text State, giving a reason, which cypher text would be more secure.
0478_m17_qp_12
THEORY
2017
Paper 1, Variant 2
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Data is encrypted to keep it safe during transmission. Complete the paragraph about asymmetric encryption. Use the terms from the list. Some of the terms in the list will not be used. You should only use a term once. asymmetric certificate cipher text decrypted encrypted parallel key plain text private key protected public key serial key symmetric is encrypted into using a . The encrypted data is then transmitted from the sender to the receiver. The encrypted data is then decrypted using a .
0478_s24_qp_11
THEORY
2024
Paper 1, Variant 1
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A library has a system that allows customers to check out the books that they want to borrow. Each book has a barcode that can be used to identify the book. Identify two input devices that may be used in the library’s system. Input device 1 Input device 2 Identify two storage devices that may be used in the library’s system. Storage device 1 Storage device 2 Identify two output devices that may be used in the library’s system. Output device 1 Output device 2 The data stored by the library is archived at the end of each day. The archive is held on a server in the library office. The data is encrypted with an 8-bit key. As some of the data is confidential, the library wants to make the encryption more secure. State how the library could make the encryption more secure. The term used to describe data before it is encrypted is plain text. State the term used to describe encrypted data. The library’s archive system uses an error detection and correction system that combines a parity check with an automatic repeat request (ARQ). Describe how this system uses the parity check and ARQ. The library has a website that customers can use to search for a book. The website has a background colour with the hexadecimal colour code #F92A10 The colour code is stored in two 12-bit binary registers. Show how the colour code would be stored in the registers. F92 A10 Videos on the library website show customers which books the library will soon have in stock. The library wants the file size of a video to be as small as possible. Identify and describe a method the library could use to reduce the file size of a video as much as possible. The library often holds events that introduce new authors. At the events, the library has a Liquid Crystal Display (LCD) screen that displays data, including an image and information about the author. Describe how an LCD screen operates to display this data.
0478_w19_qp_13
THEORY
2019
Paper 1, Variant 3
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Elsa writes a paragraph in an examination about encryption. There are several terms missing from the paragraph. Complete the paragraph using the list of given terms. Not all terms may need to be used. Some terms may be used more than once. • algorithm • alphanumeric • cookie • cypher • key • padlock • plain • word processed The data is encrypted using a . This is an that is used to scramble the data. The data before encryption is known as text. When the data has been encrypted it is known as text. To read the encrypted data it needs to be decrypted using a .
0478_w20_qp_13
THEORY
2020
Paper 1, Variant 3
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An employee has a report that they need to email to their employer. The employee compresses the report file before emailing it. State the effect the compression has on the report file. Give two benefits of compressing the report file before emailing it. The employee decides to use lossless compression to compress the file. Explain why lossy compression is not suitable. When the employee enters the email address, the computer uses Unicode to convert the email address to binary. State what Unicode is an example of. Give two advantages of the computer using Unicode instead of American standard code for information interchange (ASC. Give one disadvantage of the computer using Unicode instead of ASCII. The report is broken down into packets to be emailed. Circle three items of data that can be found in the packet header. trailer originator’s address payload interrupt input operating system destination address antivirus packet number Each packet is sent along a different path from the employee’s device to the employer’s device. Tick (✓) one box to show the name of this method of sending packets. A packet networking B packet circuiting C packet switching D packet transferring A hardware device is used to control the path that each packet takes. Give the name of this hardware device. The email data is checked for errors after it has been transmitted, using an echo check and a checksum. Explain how the echo check is used to check for errors in the email data. In the checksum error detection method, two values are compared after transmission. If the values do not match, an error is detected. Explain why the values not matching would show an error has occurred. The email data is encrypted using asymmetric encryption before it is sent. Give one reason why the email data is encrypted. Give one similarity between symmetric encryption and asymmetric encryption. Give two differences between symmetric encryption and asymmetric encryption.
0478_w24_qp_13
THEORY
2024
Paper 1, Variant 3
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Questions Discovered
8