Number Theory & Classical Cryptography (part 1) Flashcards

Quiz #2

1
Q

Greatest Common Divisor (GCD)

A

the greatest common divisor (gcd) is the largest integer that divides two numbers

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2
Q

Prime Number

A

an integer is prime if and only if its only divisors are 1 and the integer itself

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3
Q

Relative Prime Number

A

two integers are relatively prime if their only common positive integer factor is 1

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4
Q

Fundamental Theorem of Arithmetic

A

states that every integer greater than 1 can be represented uniquely as a product of prime numbers, up to the order of the factors

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5
Q

Modulus

A

given two integers a and n, mod n is the remainder when a is divided by n

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6
Q

Congruent Modulo

A

(a mod n) = (b mod n) or a = b (mod n)

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7
Q

Euler’s Totient Function

A

the number of positive integers less than n and relatively prime to n

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8
Q

Exponentiation

A

repeated multiplication

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9
Q

Plaintext

A

an original message

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10
Q

Ciphertext

A

the coded message

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11
Q

Enciphering/Encryption

A

the process of converting from plaintext to ciphertext

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12
Q

Deciphering/Decryption

A

restoring the plaintext from the ciphertext

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13
Q

Cryptography

A

the area of study of the many schemes used for encryption

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14
Q

Cryptographic System/Cipher

A

a scheme or particular algorithm

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15
Q

Cryptanalysis

A

techniques used for deciphering a message without any knowledge of the enciphering details

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16
Q

Cryptology

A

the areas of cryptography and cryptanalysis

17
Q

Substitution

A

replace one element in plaintext with another

18
Q

Transposition

A

re-arrange elements

19
Q

Symmetric

A

single-key, secret-key, conventional encryption

20
Q

Asymmetric

A

two-key, or public-key encryption

21
Q

Block Cipher

A

process one block of elements at a time

22
Q

Stream Cipher

A

process input elements continuously

23
Q

Brute-Force Attack

A

attacker tries every possible key on a piece of ciphertext until an intelligible translation into plaintext is obtained

24
Q

Unconditionally Secure

A

no matter how much time an opponent has, it is impossible for them to decrypt the ciphertext simply because the required information is not there

25
Computationally Secure
the cost of breaking the cipher exceeds the value of the encrypted information or the time required to break the cipher exceeds the useful lifetime of the information
26
Strong Encryption
encryption schemes that make it impractically difficult for unauthorized persons or systems to gain access to plaintext that has been encrypted
27
Caesar Cipher
involves replacing each letter of the alphabet with the letter standing x places further down the alphabet
28
Monoalphabetic Cipher
use a single alphabet for both plaintext and ciphertext (a single cipher alphabet is used per message)
29
Digram
two-letter combination
30
Trigram
three-letter combination
31
Playfair Cipher
treats digrams in the plaintext as single units and translates these units into ciphertext digrams (based on the use of a 5x5 matrix of letter constructed using a keyword)
32
One-Time Pad
use a random key that is as long as the message so that the key need not be repeated; key is used to encrypt and decrypt a single message and then is discarded