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Secret Key Cryptography > Chapter 2 - Basic Terminology > Flashcards

Chapter 2 - Basic Terminology Flashcards

1
Q

What is cryptography?

A
  • The making and breaking of codes and ciphers
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2
Q

What is ‘plain text’?

A
  • The message or document that you wish to keep secret
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3
Q

What is another way to refer to ‘plain text’?

A
  • Clear text
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4
Q

What format is ‘clear text’ in?

A
  • Some language the sender and receiver can both understand
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5
Q

What is a cipher?

A
  • A message or algorithm for garbling a message to make it unreadable
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6
Q

What do ciphers operate on?

A
  • individual characters or groups of characters in the text without regard to their meaning
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7
Q

What is a key?

A
  • A secret piece of information known only to the sender and legitimate receiver
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8
Q

What does the strength of a cipher depend on?

A
  • on the total size of the keys it uses
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9
Q

What is another way of refer ‘key word/phrase’?

A
  • a word or phrase used as a key
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10
Q

What is encryption?

A
  • The process of changing the plaintext into an unreadable garble by the legitimate sender who knows the key
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11
Q

What is another way of referring to ‘encryption’?

A
  • Encipherment
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12
Q

What is ‘cipher text’?

A
  • The process of changing the plaintext into an unreadable garble by the legitimate sender who knows the key
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13
Q

What is ‘decryption’?

A
  • The process that the legitimate receiver, who knows the method and the key, uses to turn the garbled ciphertext back into the original plaintext message.
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14
Q

What is another way of referring to ‘decryption’?

A
  • Decipherment
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15
Q

What is a ‘Code’?

A
  • A method for garbling a message to make it unreadable
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16
Q

How is a ‘Code’ different from a cipher?

A
  • A code normally operates on words or phrases or phrases in a message
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17
Q

What is cryptology?

A
  • The formal study of cryptography. Includes the study of mathematics and methodologies used for constructing and solving ciphers
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18
Q

What is Cryptanalysis?

A
  • The study of codes and ciphers for the specific purpose of identifying weaknesses and finding ways to break them or to strengthen them
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19
Q

What is ‘Code Breaking’?

A
  • The process of solving encrypted messages by third parties who do not have the key and may not have the method either
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20
Q

What is meant by an unbreakable cipher?

A
  • Can’t be broken by cryptographic means
  • The cipher can’t be broken in a practical sense
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21
Q

What information do you need when choosing a cipher?

A
  • How much compute and man power your opponents can expend on breaking your cipher
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22
Q

When do you have an unbreakable cipher?

A
  • When the cipher meets a target that is conservative and takes into account for advances in compute power considering your opponents compute and man power
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23
Q

What is a key factor when choosing and unbreakable cipher for it?

A
  • the lifespan of a message.
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24
Q

When has a cipher been broken?

A
  • When an opponent can read messages using the cipher
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25
Q

What is the collective term for all methods of hiding a message?

A
  • Steganography
26
Q

What are the 3 categories of modern ciphers?

A
  • Secret Key
  • Public Key
  • Personal Key
27
Q

What is a ‘secret key’ cipher?

A
  • Sender has a secret key used to encipher a message
  • Receiver has the corresponding secret key used to decipher the message
28
Q

What is a core property of a ‘key’ in a ‘secret key’ cipher?

A
  • Keys between sender and receiver can be the same or the inverse
29
Q

Who usually controls the ‘key’ in a ‘secret key’ cipher?

A
  • The sender
30
Q

What happens when the sender changes the ‘key’ in a ‘secret key’ cipher?

A
  • The sender must send the new key(or it’s inverse) to the receiver
31
Q

What is a ‘public key’ cipher?

A
  • The receiver has a public key known to everyone. The sender uses the public key to encipher the message.
  • The receiver has a secret decryption key known only to them. This key is used to decipher the message.
32
Q

What is a key factor allowing a ‘public key’ cipher to work?

A
  • The secret key can’t be computed from the public information
33
Q

What is the dominate ‘public key’ cipher?

A
  • RSA algorithm
34
Q

What is a ‘person key’ cipher?

A
  • Sender and Receiver each have a personal key they don’t share with anyone
35
Q

What are the steps a sender and receiver follow when using a ‘person key’ cipher?

A
  • pass 1 - sender enciphers the message with personal key
  • pass 2- receiver enciphers the received message with personal key and sends the message back to sender
  • pass 3 - sender deciphers the message from receiver using personal key and sends this back to receiver

after pass 3 the message is enciphered with the receivers key and receiver deciphers the message

36
Q

What is tricky about a ‘person key’ cipher?

A
  • You have to get the same result if sender encrypts first or the receiver encrypts first
37
Q

What is another way of referring to a ‘personal key’ cipher?

A
  • “Three pass protocol”
38
Q

What is the benefit of a ‘personal key’ cipher?

A
  • The sender and receiver can communicate securely without having to prearrange or transmit any key so there’s no possibility of a key being intercepted.
39
Q

What is a ‘person key’ cipher?

A
  • Sender and Receiver each have a personal key they don’t share with anyone
40
Q

What is a key characteristic of ‘public key’ cryptography?

A
  • Sender and Receiver each have a secret key
  • Sender and Receiver each have a public key available to everyone
41
Q

What is a key characteristic of ‘secret key’ cryptography?

A
  • All keys are kept secret
42
Q

What is categorizing a cipher as ‘symmetric’ or ‘asymmetric’ not particularly useful

A
  • The terms fail to capture the essential difference between public and private key cryptography
43
Q

What do block cyphers operate on?

A
  • Blocks of characters in the message
44
Q

How are blocks usually sized in a ‘block cypher’?

A
  • Blocks are usually the same size
45
Q

What is the usual size of a key that is used in a ‘block cypher’?

A
  • Keys are the same size for every block
46
Q

What do ‘stream cyphers’ operate on?

A
  • They operate on one character at a time
47
Q

What is a key characteristic of a key used in a ‘stream cipher’?

A
  • The keys are different for every character
48
Q

What is the name of a key associated with a character in a ‘stream cipher’?

A
  • Its called the ‘character key’
49
Q

Where does the character key in a ‘stream cipher’ usually come from?

A
  • It comes from a larger key called the ‘message key’
50
Q

In older stream ciphers what is a common characteristic of a message key?

A
  • The message key is repeated
51
Q

What is a cipher called if it has regularly repeating keys?

A
  • Periodic
52
Q

For newer stream ciphers what is a common characteristic

A
  • The message key is usually as long as the message
53
Q

For newer stream ciphers what is a message key called?

A
  • A ‘key stream’
54
Q

What is the difference in speed when comparing secret key vs public key cryptography?

A
  • Secret key cryptography is much faster then public key cryptography
55
Q

What is the main use of public key cryptography?

A
  • To encrypt the keys that are used for secret key encryption
56
Q

What kind of attacks is public key cryptography subject to?

A
  • Man in the middle attacks
57
Q

What kind of attacks is public key cryptography subject to?

A
  • Man in the middle attacks
58
Q

What is very important in order for public key encryption to work?

A
  • Authentication and verification of sender and receiver
59
Q

How is public key encryption different from private key encryption in terms of administrative load?

A
  • A lot of messages sent back and forth between sender and receiver for public key encryption. There is no such overhead with private key encryption
60
Q

Where is public key encryption not suitable?

A
  • When ensuring secrecy of data files stored on a computer
61
Q

What is the current standard cipher?

A
  • AES
62
Q

What is the most common public key encryption method?

A
  • RSA

Secret Key Cryptography (4 decks)

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