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GEMATMW > Cryptography > Flashcards

Cryptography Flashcards

1
Q

Goal of a Cryptosystem

A

Relay an information from one place to another without anyone else being able to know it.

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2
Q

the process of using an algorithm to transform information into a format that cannot be read.

A

Encryption

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3
Q

is the process of using another algorithm to transform encrypted information back into a readable format.

A

Decryption

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4
Q

The original information is referred to as the

A

plain text

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5
Q

encrypted version of original information is the

A

cipher text

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6
Q

Objectives of Encryption

A

Confidentiality
Integrity
Authenticity
Non-repudiation

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7
Q

The sender (let us call her Alice) and receiver (let us call him Bob) can be assured that no third party can read the message.

A

Confidentiality

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8
Q

Alice and Bob can be sure that no third party can make changes in the message.

A

Integrity

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9
Q

Bob can be sure that it is Alice who sent the message.

A

Authenticity

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10
Q

Bob can prove to any third party that Alice sent the message

A

Non-repudiation

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11
Q

example Simple Ciphers

A

Dancing Man Cipher System
Pigpen Cipher

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12
Q

If he had anything confidential to say, he wrote it in cipher, that is, by so changing the order of the letters of the alphabet, that not a word could be made out. If anyone wishes to decipher these, and get at their meaning, he must substitute the fourth letter of the alphabet, namely D, for A, and so with the others.

A

Caesar’s Cipher/ shift cipher

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13
Q

Vigenère Cipher maker

A

french diplomat, Blaise de Vigenere, 1523-1596.

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14
Q

He viewed the cipher as a substitution cipher where a different alphabet was used for the next letter of the message, with the alphabets repeating periodically — according to some key.

A

Vigenère Cipher

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15
Q

is a substitution cipher where each letter of the plain text is replaced with another letter of the alphabet. It uses a fixed key which consist of the 26 letters of a “shuffled alphabet”.

A

MONO-ALPHABETIC CIPHER SYSTEM

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16
Q

a substitution, using multiple substitution alphabets. The Vigenère cipher is probably the best-known example

The Enigma machine is more complex example

A

POLY-ALPHABETIC CIPHER SYSTEM

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17
Q

Two Basic Techniques of encryption

A

Symmetric encryption
Asymmetric encryption

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18
Q

also called secret key encryption

only has one key

A

Symmetric encryption

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19
Q

also called public key encryption

has a public key and secret key

A

Asymmetric encryption

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20
Q

introduced a new method of encryption and key management now referred to as public key cryptography.

A

W. Diffie and M. Hellman

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21
Q

system that uses a pair of keys (a PUBLIC KEY and a PRIVATE KEY).

A

Public key cryptography

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22
Q

Each individual is assigned these keys to encrypt and decrypt information.
A message encrypted by one of the two keys (the public key) can only be decrypted by the other key in the pair (the private key).

A

Public key cryptography

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23
Q

(the public key) incryptor
(the private key) decryptor

A

true

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24
Q

is available for others to use when encrypting information that will be sent to an individual.

People can use that individual’s_________ to decrypt information sent by him

A

public key

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25
Q

is accessible only to the individual.
The individual can use his _________ to decrypt any message encrypted with his public key.

A

The public key

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26
Q

means that the difference a – b is divisible by the integer n

A

Modular arithmetic

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27
Q

mathematical statement modular arithmetic

A

a ≡ b (mod n)

28
Q

RSA Cryptosystem inventors

A

Rivest, Shamir, Adleman

29
Q

is based on the assumption that factoring large integers is computationally hard.

A

RSA Cryptosystem

30
Q

a function that is easy to compute “forwards” but difficult to compute “backwards.”

A

trap door function

31
Q

It is sometimes called a one-way function.

A

trap door function

32
Q

RSA implemented two important ideas:
This use for electronic mail and for other electronic transactions and transmissions, such as fund transfers.

A

public key encryption and digital signatures.

33
Q

GOALS of Coding Theory

A

Error Detection
Error Correction

34
Q

Messages are usually transmitted in the form of binary strings (0s and 1s).

However, transmission isn’t perfect..

A

true

35
Q

Applications of Coding Theory

A

Transmission of pictures from outer space
Quality of sound in compact discs
Communication through telephone lines
Messaging through wireless communication

36
Q

is changing the message source, such as a data terminal or the human voice, to a suitable code for transmission through the channel.

A

Source Coding

37
Q

transforms the source output into a sequence of symbols which we call a “message”

A

source encoder

38
Q

is a string of 0’s and 1’s representing an actual message.

A

codeword

39
Q

determined by the number of digits.

A

length

40
Q

the collection or set of all codewords

A

Code

41
Q

“received word“ is reverted back to a “message“

A

Decode

42
Q

A bit string is said to have ________ depending on the number of 1s in the string.

A

odd parity or even parity

43
Q

0010110 parity
0101110 parity

A

has odd
has even

44
Q

The simplest possible error-correcting code

e.g. if 1010 is the intended message,
We repeat each bit a certain times, say three times, and we obtain

A

Repetition Codes

45
Q

One approach would be to compute the Hamming distance between y and each of the codewords in C.

Then, to decode y, we take the codeword of minimum Hamming distance from y, if such a codeword is unique

A

Nearest Neighbor Decoding

46
Q

distance between two codewords is the number of bits where the two words differ

A

The Hamming distance

47
Q

of a code is the smallest distance between any two distinct codewords in the code.

A

minimum distance

48
Q

minimum Hamming distance 2e+1. Then

It is possible to detect up to 2e errors.

It is possible to correct up to e errors.

A

TRU

49
Q

minimum Hamming distance 2e+1. Then

It is possible to detect up to 2e errors.

It is possible to correct up to e errors.

A

true

50
Q

are used for easy identification of products as well as for tracking and inventory purposes.

A

Product Tag

51
Q

Each time product tags are typed or scanned into computer or transmitted in some other fashion, there is a chance that one or more digits in the number will change or be rearranged as they move from one location to the other.

A

trye

52
Q

Nearly every item that you purchase from a grocery store and department store it has this code

A

Universal Product Code (UPC)

53
Q

originally created to help grocery stores speed up the checkout process and keep better track of inventory

A

bar codes

54
Q

The last digit x12 is called a
digit lets the system determine if it scanned the number correctly or not. Given the eleven-digit string x1x2 … x11, the check digit x12 is appended such that the whole twelve-digit “codeword” satisfies

A

check digit

55
Q

Universal Product Code (UPC) formula

A

3𝑥_1+𝑥_2+3𝑥_3+𝑥_4+⋯+3𝑥_11+𝑥_12≡0mod10

56
Q

It is design to allow high speed component scanning.
It is detected as a 2-dimensional digital image by a semi-conductor image sensor.

The sensor locates the three distinctive squares at the corners of the image, and uses a smaller square near the fourth corner to normalize the image for size, orientation, and angle of viewing. The small dots are then converted to binary numbers and their validity checked with an error-correcting code.

A

Quick Response Code or QR Code

57
Q

Quick Response Code or QR Code made by

A

Japan By Denso-Wave in 1994.

58
Q

THE FATHER OF COMPUTER SCIENCE

A

ALAN TURING

59
Q

joined the Government Codes and Cypher School at Bletchley Park. He developed a machine (The Bombe) which helped break the code for the German Enigma machine (a device for sending coded messages to units of the German forces).

A

ALAN TURING

60
Q

means cover writing.

is less popular

structure of data can not be altered.

Confidentiality and Authentication security principles.

A

Steganography

61
Q

means Secret writing.
is more popular than Steganography.
structure of data can be altered.
supports Confidentiality and Authentication
security principles as well as Data integrity and Non-repudiation.

A

Cryptography

62
Q

Attack’s name in Steganography is

A

Steganalysis.

63
Q

While in cryptography, Attack’s name is

A

Cryptanalysis.

64
Q

Encryption Process formula

A

eme

65
Q

Decryption Process formula

A

eme

GEMATMW (3 decks)

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