codes & ciphers

Question 1

utilizes a set of symbols to represent an object

Answer 1

code
Ex: “A” can be replaced by a string of “0’s” and “1’s”, say 00101

Question 2

a scheme to conceal information by switching letters or representing them with other symbols

Answer 2

ciphers

Question 3

It is used heavily in communication and data transmission.

Answer 3

ciphers

Question 4

briefly explain cryptology

Answer 4

plain text —-> cipher text (cryptography)

cipher text —-> plain text (cryptanalysis)

Question 5

define coding theory

Answer 5

the study of methods for efficient and accurate transfer of information

detect and correcting transmission errors

deals with the design of error-correcting codes for the reliable transmission of information across noisy channels

make use of classical and modern algebraic techniques (finite fields, group theory and polynomial algebra)

Question 6

ISBN

Answer 6

international standard book number

Question 7

it regulates and keep track of various publications in different
parts of the world

Answer 7

ISBN international standard book number

Question 8

how many digit code are there in the
ISBN
UPC

Answer 8

ISBN:
10 digit code to 13 digit code. expanded in 2007

UPC:
12 digit code

Question 9

who takes charge of the ISBN registration, allocation, and designation for Filipino publishers
and authors

Answer 9

the national library of the Philippines (NLP)

Question 10

in ISBN ,
the first 3 digit =
the fourth digit =
remaining digits except the last =
last digit =

Answer 10

the first 3 digit = 978 or 979
the fourth digit = country code
remaining digits except the last = identify the author and the title of the book
last digit = check digit

Question 11

UPC

Answer 11

universal product code

Question 12

in UPC,
the last digit =

Answer 12

the last digit = check digit

Question 13

in Philippines, what are the dominant cards in the market
and how many digit numbers

Answer 13

Visa
Mastercard

normally having 16 digit numbers except for some Visa cards that have 13 digits only

Question 14

define binary codes

Answer 14

it refers to a string of 0’s and 1’s

Question 15

in binary codes, define bit and byte

Answer 15

bit: each character in the string
byte: a series of 8 bits

Question 16

each key in the keyboard of a computer corresponds to a binary code of at least how many bits

Answer 16

5

Question 17

how are computers are able to to translate letters and symbols into binary codes

Answer 17

using the American Standard Code for Information Interchange (ASCII codes)

Question 18

define hamming code
and it is introduced by

Answer 18

a scheme for error correction
introduced by R. W. Hamming

Question 19

hamming code uses what redundant bit

Answer 19

parity bit (aka check bit)
it is either ‘even’ or ‘odd’ depending on whether there is an even or odd no. of 1’s

Question 19

why does coded messages tend to be very prone to distortion when being transmitted to available medium

Answer 19

because of the presence of some environmental interference or unforeseen defects in the transmission medium

Question 19

in hamming codes, what happens if there is any changes that may occur in a message that may alter its original meaning

Answer 19

error

Question 19

define:
cryptography -
encryption -
decryption -

Answer 19

cryptography - process of converting data ort info into codes, primarily for the purpose of keeping it secured. it involves encryption and decryption

encryption - converts a message into meaningless and usually unreadable formats that only the intended recipient can understand

decryption - process of recovering the encrypted information

encryption is like locking a message in a box with a special key, and decryption is like using the same key to unlock the box and retrieve the original message. Cryptography ensures that only authorized parties with the correct key can access the sensitive information, while preventing unauthorized access or eavesdropping

Question 19

it is a process by which information is shared among individuals

Answer 19

communication

Question 20

what is shift cipher

Answer 20

it uses the natural order of the letters on the english alphabet

goal: replace the letters of a given message by another letter which is at some fixed number of positions according to the natural order of the letters

Question 21

formula of shift cipher

Answer 21

C = (P + K) mod 26
P - original position of a letter in the given message
C - shifted position (code letter)
K - constant that determines the fixed number of shift positions

Question 22

what is affine cipher