SRSS 2019 P1 Solution

1 \Serangoon Secondary Computing Sec 4E 2019 Preliminary Exams (Marking scheme) Q1) [5] Network Term Description Q2) IP Address MAC Address Service Set Identifier Ring Topology Star Topology An identifier that is automatically assigned by a router. It is required to receive and forward data packets out of a network A network configuration that requires a central device such as a hub or a bridge to manage the transmission of data. A 32-byte long string that identifies a wireless access point and all devices connected to it. A network configuration where the entire network may fail whenever any computer in the network fails. An identifier that is required to receive and forward data packets within a network through a network bridge. A network configuration where all computers are connected together through a single common cable.

2 a) (10000101)2 = (1*128) + (1*4) + (1*1) = 133 or (133)10 [2] b) F16 = (1111)2 B16 = (1011)2 (FB)16 = 11111011 or (11111011)2 [2] c) (11110)2 = (0001 1110)2 = ( 1 E )16 = 1E or (1E)16 [2] d) (365)16 = (3 x 162) + (6 x 161) + (5 x 160) = 869 [2] Q3) (a) (i) [5] Highest Num1 Num2 Range i 1 15 6 15 1 1 6 2 3 3 4 5 6 (ii) [1] • Find the highest common factor of 2 inputs • Find the largest common factor of 2 inputs • Find the greatest common factor of 2 inputs (b) (i)

3 [2] Validation check: Presence check Description: To check that the user has entered a value in the inputs Validation check: Format check Description: To check that the user has entered only numbers in the inputs Validation check: Length check Description: To check that the user has entered at least 1 character/digit in the inputs Validation check: Range check Description: To check that the user has entered numbers greater than zero (ii) [2] • Presence check • Length check • Format check • Range check (c) [4] Test Case Condition Test Data Boundary condition 1, 1 Error condition 0, 10 Q4) (a) [2] • Poor authentication • Poor access control or authorization • Poor understanding of privacy policies (b) [2] • Use of passwords

4 • Use of security tokens • Use of Biometrics • Setting file permissions • Use of firewalls • Encryption of files (password protecting of files) • Reading and fully understanding privacy policies on use of services online • Use of anti-virus software (c) [4] • Cookies. Personal information stored in cookies can be stolen and misused. • Pharming. Interception of requests sent from a computer to a legitimate website and redirecting the user to a fake website to steal personal information. • Phishing. Sending of emails/text messages from fake websites that appear to be from legitimate reputable companies (e.g. banks). Users who are unaware will submit personal information to the phishing websites. • Spamming. Mass distribution of unso