codes & ciphers Flashcards
utilizes a set of symbols to represent an object
code
Ex: “A” can be replaced by a string of “0’s” and “1’s”, say 00101
a scheme to conceal information by switching letters or representing them with other symbols
ciphers
It is used heavily in communication and data transmission.
ciphers
briefly explain cryptology
plain text —-> cipher text (cryptography)
cipher text —-> plain text (cryptanalysis)
define coding theory
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)
ISBN
international standard book number
it regulates and keep track of various publications in different
parts of the world
ISBN international standard book number
how many digit code are there in the
ISBN
UPC
ISBN:
10 digit code to 13 digit code. expanded in 2007
UPC:
12 digit code
who takes charge of the ISBN registration, allocation, and designation for Filipino publishers
and authors
the national library of the Philippines (NLP)
in ISBN ,
the first 3 digit =
the fourth digit =
remaining digits except the last =
last digit =
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
UPC
universal product code
in UPC,
the last digit =
the last digit = check digit
in Philippines, what are the dominant cards in the market
and how many digit numbers
Visa
Mastercard
normally having 16 digit numbers except for some Visa cards that have 13 digits only
define binary codes
it refers to a string of 0’s and 1’s
in binary codes, define bit and byte
bit: each character in the string
byte: a series of 8 bits
each key in the keyboard of a computer corresponds to a binary code of at least how many bits
5
how are computers are able to to translate letters and symbols into binary codes
using the American Standard Code for Information Interchange (ASCII codes)
define hamming code
and it is introduced by
a scheme for error correction
introduced by R. W. Hamming
hamming code uses what redundant bit
parity bit (aka check bit)
it is either ‘even’ or ‘odd’ depending on whether there is an even or odd no. of 1’s
why does coded messages tend to be very prone to distortion when being transmitted to available medium
because of the presence of some environmental interference or unforeseen defects in the transmission medium
in hamming codes, what happens if there is any changes that may occur in a message that may alter its original meaning
error
define:
cryptography -
encryption -
decryption -
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
it is a process by which information is shared among individuals
communication
what is shift cipher
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
formula of shift cipher
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
what is affine cipher
