Error Detection

Question 1

even parity

Answer 1

checks to see that the total of 1s is even

Question 2

odd parity

Answer 2

checks to see that the total of 1s is odd

Question 3

limitation of parity check

Answer 3

cant tell exactly which bit was corruptd

Question 4

checksum

Answer 4

method in which data is sent in chunks with a calculated value (if there is a mismatch, receiving will ask sending to resend data)

Question 5

how to calculate checksum

Answer 5

1: if number of the bytes is less or equal to 255, this value is the checksum
2: if greater than 255:
- divide sum of bytes by 256 to get quotient
- convert quotient to integer (round down)
- multiply the integer by 256 to get the product
- subtract product from sum

Question 6

echocheck

Answer 6

method where receiving device. sends back an exact copy of data to th sending, which compares the data with the originally sent. if there is an error, data is resent and process repeats

Question 7

disadvantage of echo check

Answer 7

difficult to know if data was corrupted when first sent or on the way back

Question 8

check digit

Answer 8

extra digit added to a number that is calculated from the existing digits int he number

Question 9

examples of check digit

Answer 9

ISBN, VIN

Question 10

automatic repeat request (ARQ)

Answer 10

set of rules established between sending and receiving devices to control errors. if error is detected, it can request the sending to resend the packet

Question 11

what happens when data is received in ARQ

Answer 11

the computer sends a message known as acknowledgement (ACK)

Question 12

acknowledgement

Answer 12

indicates whether thee transmission was successful or not (positive and negative). whole process repeats until confirmation or timeout (time allowed to elapse)

Question 13

encryption

Answer 13

way to conceal information by altering it soo it appears to be random to someone that is not supposed to read it

Question 14

how does encryption happen

Answer 14

using hypertext transfer protocol secure (HTTPS)

Question 15

what does https use

Answer 15

secure socket layer (ssl) and transport layer security (tls)

Question 16

plain text

Answer 16

text that has not been encrypted

Question 17

cipher text

Answer 17

text that has been encrypted

Question 18

how does caeser cipher work

Answer 18

right shift of 3 on alphabet

Question 19

types of encryption

Answer 19

symmetric and asymmetic

Question 20

symmetric

Answer 20

same key is used to encrypt and decrypt

Question 21

disadvantage of symmetric

Answer 21

if key is intercepted, user can read message

Question 22

asymmetric

Answer 22

two keys; encrypt (public) and decrypt (private)

Question 23

which encryption is more reliable

Answer 23

asymmetric

Question 24

why is error detection needed

Answer 24

Errors can occur during data transmission due to interference, e.g. data loss, data gain and data change