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Security+ UDemy > Section 24 - Crytography > Flashcards

Section 24 - Crytography Flashcards

1
Q

What is cryptography?

A

The practice and study of writing and solving codes in order to hide the true meaning of the information

This is done by converting ordinary information known as “plaintext” into an unintelligible format known as “ciphertext”

*** This is most commonly used as a form of encryption

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2
Q

Encryption is used to provide us data…?

A

Data at rest
Data in transit
Data in use

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3
Q

What is data at rest?

A

It’s inactive data that is archived such as data that’s resident on a hard drive

*** Example of this is just data sitting there in a file

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4
Q

What is data in transit?

A

Data that’s cross the network or data that’s residing inside the computer’s memory, the RAM, as it’s waiting to be processed

*** This is when we start moving that data around

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5
Q

What is data in use?

A

Data in use means it is currently undergoing constant change

*** So there’s data inside your processor and calculations are being done

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6
Q

What is an algorithm?

A

A mathematical formula that tells you how we’re going to encrypt or decrypt something

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7
Q

What is the key in an algorithm?

A

The essential piece of information that determines the output of a cipher

*** The key is the key to the security inside encryption

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8
Q

Encryption ciphers are categorized as either…?

A

Symmetric or asymmetric algorithms

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9
Q

The type of encryption cipher is based on the ___ that they utilize to secure the data.

A

Key

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10
Q

With a symmetric key encryption, you’re going to have a ___ key that’s used to encrypt and decrypt data.

A

single

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11
Q

With asymmetric encryption, you’re going to use ___ ___ keys.

A

two different

** one key is used to encrypt the data and one key is used to decrypt the data

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12
Q

Symmetric key algorithms are often called what?

A

Private Key Encryption

*** This is because the sender and the receiver need to know the same shared secret, the key, since it only uses a single one.

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13
Q

What are two challenges with using Symmetric Key algorithms?

A
  1. Due to non-repudiation, it can be a challenge to prove who used the key. So, if you live in a house with several roomates then you all share the same house key. But if your laptop get stolen while you’re out, you won’t know which of those roomates took it.
  2. Distribution of that shared secret key
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14
Q

Asymmetric algorithms are often referred to as…?

A

Public Key Cryptography

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15
Q

In addition to classifying algorithms as symmetric or asymmetric based on their key type, we also categorize an algorithm as a ___ ___ or a ___ ___ based on the mathematical algorithm that they’re using to do their encryption/decryption.

A

stream cipher

block cipher

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16
Q

What are the differences between stream ciphers and block ciphers?

A

Stream ciphers perform their computations a single byte at a time. Making it a bit by bit process. A block cipher is able to break the input into fixed length blocks of data before performing encryption.

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17
Q

What is hybrid implementation?

A

Utilizes asymmetric encryption to securely transfer a private key that can then be used with symmetric encryption

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18
Q

What are some common symmetric algorithms that you should know?

A

DES
triple DES
IDEA
AES
Blowfish
Twofish
Rivest Ciphers
RC4
RC5
RC6

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19
Q

What is DES?

A

Data Encryption Standard

This uses a 64 bit key with 8 bits of that being used for parity

*** This means it only has an effective key length of 56-bits

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20
Q

What is triple DES?

A

Written as 3DES this is an upgraded version of the original DES.

There are three 56-bit keys used.

The input data was subjected to encryption through the DES algorithm with the first key and decrypted through the algorithm using the second key

This created an algorithm that had a 112-bit key but was three times slower than DES because of all the back and forth encryption

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21
Q

What is IDEA?

A

International Data Encryption Algorithm

A symmetric block cipher that uses 64-bit block as it’s input and uses that to encrypt the data. The key size here is 128-bits

*** Commonly known due to working well within a privacy suite

22
Q

What is AES?

A

Advanced Encryption Standard

This can be used with a 128-bit, 192-bit, or 256-bit key and a matching block size.

23
Q

AES is also known as what?

A

Rijndael algorithm

*** Named after its creator

24
Q

This encryption standard is widely used and has become the de facto standard in encryption.

A

AES

25
Q

What is Blowfish?

A

This is a block cipher that uses a 32-bit to 448-bit encryption key to encrypt 64 bits of data in blocks at a time

*** This was developed as a replacement for DES but wasn’t widely utilized.

26
Q

What is Twofish?

A

A variant of Blowfish, this can use 128-bit blocks in its encryption algorithm and use 128-bit, 192-bit, or 256-bit encryption keys.

27
Q

What two encryption algorithms were never patented and were available for use as open source?

A

Blowfish and Twofish

28
Q

This set of six symmetric algorithms was created by Ron Rivest under the name…?

A

RC

Rivest Cipher

29
Q

How did RC’s algorithms do?

A

RC1 - never published
RC2 - considered weak and skipped over
RC3 - cracked before released to the public
RC4, RC5 and RC6 are in common use today

30
Q

This is a stream cipher and it uses a variable key size from 40 bits all the way up 2048-bits.

It is used in both Secure Sockets Layer (SSL) and Wired Equivalent Privacy (WEP)

A

RC4

*** It is important to remember that this is the only symmetric stream cipher we’ve talked about. All others are block ciphers.

31
Q

This is a block cipher using key sizes up to 2048-bits

A

RC5

32
Q

This cipher was based on the RC5 and was considered a replacement for DES until it became the AES.

A

RC6

33
Q

With asymmetric algorithms, we use a key pair to encrypt and decrypt the data. These two keys are called…?

A

Public Key
Private Key

34
Q

What is a digital signature?

A

A hash digest of a message encrypted with the sender’s private key to let the recipient know the document was created and sent by the person claiming to have sent it

35
Q

What does PKI stand for?

A

Public Key Infrastructure

36
Q

What are some asymmetric algorithms?

A

Diffie-Hellman
RSA
ECC

37
Q

How does the asymmetric Diffie-Hellman algorithm work?

A

This is used to conduct key exchanges and secure key distribution.

This is widely used to set up VPN tunnels and other encryption tunnels that require a symmetric algorithm’s shared secret key, that private key, to be exchanged first before setting up that symmetric tunnel.

*** Highly susceptible to man-in-the-middle attacks so make sure you’re requiring a password or digital certificate at the beginning of the exchange process

38
Q

How does the asymmetric RSA algorithm work?

A

The name comes from its creators, (Rivest, Shamir and Adleman)

This is widely used for key exchange, encryption and digital signatures.

It relies on the difficulty of mathematically factoring large prime numbers to protect its public and key pairs.

This supports key sizes between 1024-bits and 4096-bits.

39
Q

How does the asymmetric ECC algorithm work?

A

Elliptic Curve Cryptography

This is heavily used in mobile devices and is based on algebraic structure of elliptical curves over finite fields to define its keys.

40
Q

There are a few variations of ECC. What are they?

A

ECDH - the ECC version of Diffie-Hellman

ECDHE - uses a different key for each portion of the key establishment process inside of ECDH

ECDSA - used by the Government for their digital signatures

** All of these variants are most commonly used for mobile devices and low-power computing devices

41
Q

What is PGP?

A

Pretty Good Privacy

This is an encryption program that’s used for signing, encrypting and decrypting emails.

This is a HYBRID cryptographic tool. It uses a symmetric cipher for the bulk data encryption but uses RSA, an asymmetric cipher) to create digital signatures

This has moved beyond emails and can also encrypt files and entire hard disks.

*** This became an open source cipher and thus resulted in GPG

42
Q

What is the difference between PGP and GPG?

A

PGP uses an older algorithm (IDEA)

GPG uses AES

43
Q

What is GPG?

A

GNU Privacy Guard

This is an implementation of cryptography that’s used to provide you with confidentiality in your data by encrypting it like PGP.

44
Q

What is One-Time Pad?

A

A stream cipher that encrypts plaintext information with a secret random key that is the same length as the plaintext input.

Computers are unable to create one-time pads because there is no real mathematical formula or pattern to them and computers are never truly capable of being random. Computers are always operating on logic and math.

For the reason above, these aren’t often used. Instead, the concept of one-time passwords was formed.

*** This is the ONLY truly unbreakable cipher that exists because all of the numbers are random.

45
Q

What is a keystream?

A

A keystream is the secret random key within a One-Time Pad

It is comprised of a series of random bits

46
Q

What is PRNG?

A

Pseudo-Random Number Generator

This is an algorithm that spits out what looks like random numbers but to other computers they can figure out what the initial seed was and then that takes away the randomness

*** This is a computers attempt to simulate creating random numbers using algorithms

47
Q

How do one time passwords work?

A

Used in multi-factor authentication, a “random number” is texted to you by your website whenever you attempt to log in. Or you could have an RSA secure token display pseudo-random numbers that you use to prove you have possession of that token as your second fact of authentication.

48
Q

What is steganography?

A

The science and art of hiding message within other messages

*** This is a form obfuscation, not encryption. This data isn’t encrypted but rather it is hidden within another message.

49
Q

What is homomorphic encryption?

A

An encryption method that allows calculations to be performed on data without decrypting it first

*** This is a great use on a cloud provider because if they need to work on your data you can encrypt it with something that supports homomorphic encryption and they can still do the calculations for you without ever seeing the data that’s inside that encryption.

50
Q

What is ephemeral cryptography/keys?

A

This is a cryptographic key that is generated for each execution of a key establishment process.

*** All that you need to know is that these are short lived. You pick one for a short time and then throw them away. Like ephemeral ports, we pick a port, use it to create a connection and then when we’re done with that session we throw it away and close that port. It’s the same thing with ephemeral keys.

51
Q

What is a blockchain?

A

A shared immutable ledger for recording transactions, tracking assets, and building trust.

Essentially, a really long series of information. And each block contains information in it. That block is this ledger. In it, you’re going to have the previous hash from the block before it. There are millions of blocks within a blockchain.

*** An example of this is cryptocurrencies, like bitcoin.

52
Q

What is a public ledger?

A

A record keeping system that maintains participants identities in a secure and anonymous form.

Security+ UDemy (33 decks)

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