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Sec Plus > Cryptography > Flashcards

Cryptography Flashcards

1
Q

Confidentiality

A

Only authorized parties can access data.

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2
Q

Integrity

A

Verifying data has not been altered in transit.

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3
Q

Authentication

A

Verifying the sender is who they say they are.

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4
Q

Non-Repudiation

A

Prevents one party from denying actions they carried out.

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5
Q

Cryptography

A

“Science of secret writing”

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6
Q

Cryptanalysis

A

Study and practice of finding weaknesses in ciphers

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7
Q

Algorithm

A

“Formulas to encrypt data”

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8
Q

Cipher

A

Method used to encode characters to hide their value

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9
Q

Plain Text/Clear Text

A

Info which is transferred or stored without crypto protection

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10
Q

Cipher text

A

Result of encryption performed on plaintext using an algorithm.

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11
Q

Substitution Cipher

A

One character or symbol into another

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12
Q

Substitution Code

A

Substitution at the level of words or phrases

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13
Q

Transposition

A

Changing the positions of plaintext letters within a sentence.

eg. meet me at noon = noontaemteem

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14
Q

Exclusive-OR (XOR) Operation

A

Binary mathematical operation

If values are the same = 0
If values are different = 1

Used in One-Time Pad

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15
Q

One-Time Pad

A

Considered Unbreakable

3 Requirements:

  1. Made up of truly random values and used only once
  2. Must be at least as long as the message
  3. Securely distributed to destination and protected at sender’s and receiver’s sights.

Cons: More overhead, needs to be received in a secure fashion, sender/receiver must be perfectly synched.

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16
Q

Frequency Analysis

A

Study of the frequency of letters or groups of letters in a cipher text.

Eg. Wheel of Fortune

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17
Q

Initialization Vectors

A

Random values used with algorithms to ensure patterns are not created during encryption process.

Not encrypted when being sent

Used in WEP

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18
Q

Steganography

A

Electronic Watermarking

Hiding one’s message in another in order to prevent it from being detected.

Graphics/Sound Files

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19
Q

ADS

A

Alternate Data Streams

Adds a program on to another to help it work across multiple platforms.

Can be used for evil.

Eg. Drive in movie with someone in the trunk.

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20
Q

Quantum Cryptography

A

Message is sent in a series of photons. Receiver must know sequence and polarity of photons to decode message.

If someone intercepts, some of the photons will change polarity and message will be altered.

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21
Q

Hashing

A

Used for Integrity

One-way encryption function. Takes variable-length input and makes a fixed-length output.

Hash collision happens when different inputs create the same hash value. Collision detection prevents this.

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22
Q

MD5

A

Message Digest 5
Hash Function (Cisco)
Digest Size: 128 bits

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23
Q

SHA-1

A

Secure Hashing Algorithm
Hash Function
Digest Size: 160 bits

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24
Q

SHA-2/SHA-224/256

A

Secure Hashing Algorithm
Hash Function
Digest Sizes: 224, 256 bits

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25
Q

SHA-2/SHA-384/512

A

Secure Hashing Algorithm
Hash Function
Digest Size: 512 bits

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26
Q

RIPEMD-160

A

Hash Function

Digest Sizes: 128, 160, 256, 320 bits

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27
Q

HAVAL

A

Hash Function

Digest Sizes: 128, 160, 192, 224, 256 bits

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28
Q

Whirlpool

A

Hash Function

Digest Size: 512

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29
Q

Brute Force Attacks

A

Applying every possible combination of characters that could be the key.

Time may be a factor/not fast enough

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30
Q

Dictionary Attack

A

Uses dictionary of common words (to include proper nouns)

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31
Q

Rainbow Table/Crack

A

Uses a lookup table comprised of pre-calculated hash from common words.

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32
Q

Birthday Attack

A

Probability that someone has the same hash that attacker has already figured out.

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33
Q

SALT

A

Randomly generated value that is calculated into the hashing process

eg. Table Salt

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34
Q

MAC

A

Message Authentication Code

Verifies integrity and origin
Symmetric Key

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35
Q

HMAC

A

Hashed Message Authentication Code

Hash function added to MAC

Adds symmetric key to data to be hashed.

Used in IPSec, SSL/TLS, SSH

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36
Q

Symmetric Cryptography

A
  • Uses one key to encrypt/decrypt info
  • Both parties share same key
  • Best for bulk encryption; faster (smaller key) than asymmetric
  • AKA: secret key, private key, shared key, same key, single key, session key
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37
Q

Stream Cipher

A

Symmetric Encryption Method

  • Bit by bit
  • Keystream
  • Hardware
  • No memory
  • On-the-fly
  • Very fast
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38
Q

Block Cipher

A

Symmetric Encryption Method

  • Software
  • Fixed-length blocks
  • Block-by-block
  • Uses substitution/transposition ciphers
  • Stronger than stream-based
  • Slow/resource intensive
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39
Q

Symmetric Encryption Methods

A

Stream Cipher and Block Cipher

Pros:

  • Less computationally intensive
  • Produces smaller file size
  • Faster transmissions

Cons:

  • Key distribution security
  • Needs to be trust between parties
  • Key management (n(n-1)/2=# keys needed
  • No “non-repudiation”
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40
Q

Symmetric Key Algorithms

A 
C - CAST
3 - 3DES
2 - Twofish
B - Blowfish
R - RC4, 5, 6
A - AES
I - IDEA
D - DES
S - SAFER (+, ++)
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41
Q

DES

A

Data Encryption Standard/Symmetric

Based on IBM’s Lucifer algorithm
64-bit Block (56-bit key + 8 bits for parity)
Algorithm: DEA (Data Encryption Algorithm)
Easily Broken

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42
Q

3DES

A

Triple DES/Symmetric

Upgrade of DES (still in use)
Applies DES three times
168-bit key (+24 bits for parity)

43
Q

AES

A

Advanced Encryption Standard/Symmetric

Current standard replaced DES
128 bit block
Algorithm: Rijndael
Key Sizes: 128, 192, 256 bits

44
Q

Blowfish

A

Symmetric

Fastest of the symmetric
64 bit block cipher
Variable-length keys (32-448 bits)

45
Q

Twofish

A

Symmetric

128 bit block cipher
Variable length keys (128, 192, 256 bits)
Finalist for AES

46
Q

CAST

A

Carlisle Adams and Stafford Tavares/Symmetric

Used by PGP

CAST-128:

  • 64 bit block size
  • Variable key lengths (40-128 bits)

CAST-256:

  • 128 bit block size
  • Variable key lengths (128, 160, 192, 224, 256 bits)
47
Q

RC

A

Rivest Cipher/Symmetric

RC4 (stream): Variable key length (0-2048 bits)

RC5 (block): Variable block (32, 64, 128 bits)
* Variable key length (0-2048)

RC6 (block): Variable block (128)
* Variable key length (0-2048)

48
Q

IDEA

A

International Data Encryption Algorithm/Symmetric

64 bit block
128 bit key length
Developed by the Swiss
Used in PGP and other encryption software

49
Q

Skipjack

A

Symmetric

Block cipher
NSA
Clipper chip

50
Q

SAFER

A

Secure And Fast Encryption Routine/Symmetric

Used in Bluetooth
For key derivation NOT for encryption

SAFER+:
* 128 bit block cipher

SAFER++:
* 64, 128 bit block cipher

51
Q

Asymmetric Cryptography

A

Public Key Encryption

Each user has two keys: Private/Public
Keys are mathematically related

Pros:

  • Key Management (n*2)
  • Public key can be freely distributed
  • Offers: digital signatures, integrity, key exchange, non-repudiation

Cons:

  • Slower than symmetric
  • Larger encryption file
52
Q

Asymmetric Key Algorithms

A

D- Diffie-Hellman
E- ElGamal
E- ECC
R- RSA

53
Q

Diffie-Hellman

A

Asymmetric

Based on difficulty of computing discrete logarithms
Key exchange
Variable key length: 512, 1024-2048 (secure)

Same strength as 3072 bit RSA key

54
Q

El Gamal

A

Asymmetric

Encryption, Digital Signatures, Key Exchange
Based on Diffie Hellman
Slow

Open standard/Legacy

55
Q

RSA

A

Rivest, Shamir, Adleman/Asymmetric

Encryption, Digital Signatures, Key Exchange
De facto standard
Based on difficulty of factoring N (prod of 2 large prime #)
Variable block and key length
* 512 bit to arbitrarily long
* 1024-2048 considered secure

Used in PGP

56
Q

ECC

A

Elliptic Curve Cryptography/Asymmetric

Encryption, Digital Signatures, Key Exchange
Based on using points on a curve to define public/private key
Key of 160 bis is equal to 1024 RSA key
Hardware such as wireless devices and smart cards

57
Q

Three Things Needed to Create a Digital Signature

A
  • Email message
  • Hashing Algorithm
  • Sender’s Private Key
58
Q

Digital Signature Process

A

Sender:

  • Creates email message
  • Creates message hash
  • Uses private key to encrypt hash
  • Hash becomes digital signature and is sent with message

Receiver:

  • Hashes received message
  • Uses sender’s public key to decrypt
  • If hashes match message is valid and sender is verified
59
Q

DSA

A

Digital Signature Algorithm

Used only for digital signatures
Does not provide confidentiality
Public key algorithm with var key size from 512-4096 bits
Follows NIST/FIPS DSS and goes up to 1024 bits
Uses SHA-1 for integrity
Faster than RSA at verifying signatures

60
Q

Two Goals of DSA

A

Provide authentication and integrity

61
Q

Hybrid Cryptosystem

A

Symmetric for data encapsulation
Asymmetric for key encapsulation
Cryptographic hash can be used to provide data integrity

Eg. PGP, S/MIME, TLS, SSH, IPSec

62
Q

SSL

A

Secure Socket Layer

Secure connection between two TCP-based machines
Uses X.509v3
TCP Port 443

63
Q

SSL Vulnerabilities

A

Small key size
Expired digital certificates
Compromised keys

64
Q

SSL Provides:

A
  • Confidentiality: AES, IDEA, 3DES, DES, RC4, RC2
  • Message Integrity: SSLv3 MAC w/ shared key (similar to HMAC) with MD5 or SHA1
  • Key Exchange: RSA, Diffie Hellman

Ability to implement Mutual Authentication

65
Q

SSL Can Be Used to Secure:

A

Telnet, NNTP, FTP, HTTP, SMTP, IMAP

66
Q

TLS

A

Transport Layer Security

Secure connection between two TCP-based machines
Operates like SSSL
More secure hashing than SSL
TCP Port 443

67
Q

TLS Provides:

A

Confidentiality: AES, IDEA, 3DES, DES, RC4, RC2
Message Integrity: HMAC
Key Exchange: RSA and Diffie-Hellman
More alert codes that SSL

68
Q

HTTPS vs S-HTTP

A

HTTPS:

  • HTTP over SSL
  • TCP Port 443
  • Encrypts communication channel

S-HTTP:

  • Dev by Netscape
  • Provides security over standard page requests
  • TCP Port 80
  • Encrypts INDIVIDUAL MESSAGES
  • Does not require client-side public key certs (symmetric key only)
69
Q

SSH

A

Secure Shell

Secures remote terminal communications
Secure replacement for Telnet and FTP
TCP Port 22
Encrypts data w/ symmetric algorithm
Est connection and authentication using public key crypto

Eg. PuTTY and OpenSSH

70
Q

SMTP

A

Transmits mail from e-mail clients to e-mail servers and between e-mail servers
TCP port 25

71
Q

POP3

A

Downloads e-mail from an inbox on an e-mail server to an e-mail client
TCP port 110

72
Q

IMAP4

A

Downloads e-mail from an inbox on an e-mail server to an e-mail client
TCP port 143

73
Q

MIME

A

Multipurpose Internet Mail Extensions

Defines how e-mail clients handle non-plaintext content.

74
Q

S/MIME

A

Secure Multipurpose Internet Mail Extensions

Uses X.509 Standard
Protection for email and attachments
Provides: Authentication, Integrity, Confidentiality, non-repudiation
Uses: AES, 3DES, DES, RC2
Key Exchange: Diffie-Hellman with DSS or RSA
SHA-1 and MD5

75
Q

x.509 Standard

A

ITU standard for defining digital certificates
Defines the formats and fields for public keys
Defines procedures for distributing public keys

76
Q

PGP

A

Pretty Good Privacy

E-mail encryption system
Web of Trust NOT X.509
GPG = open source version
Asymmetric: RSA, DSS, Diffie-Hellman
Symmetric: AES, IDEA, CAST-128, IDEA, Twofish, 3DES
Hash Coding: SHA-2, SHA-1, MD5 RIPEMD-160

77
Q

Typical Certificate Contains (6):

A 
Issuer's name
Valid date / to date
Owner (subject)
Subject's public key
Time stamp
Certificate issuer's digital signature
78
Q

PKI

A

Public Key Infrastructure

  • Framework for managing private keys and certificates
  • Follows X.509 standard
  • Standard for key generation, authentication, distribution and storage
  • Est who is responsible for authenticating the ID of the owners of the digital certificate
79
Q

CA

A

Certificate Authority

Organization responsible for issuing, storing, revoking and distributing certificates

Authenticates the certificates by signing them with their private key

80
Q

RA

A

Registration Authority

  • Middleman between CA and subscribers
  • Can distribute keys, accept registrations for CA and validate identities
  • Does not issue certs on their own
81
Q

Digital Certificate Enrollment Process

A
  • Subject must prove ID to CA before cert is created
  • Give info physically appearing w/ and agent ID, credit report data, etc.
  • Once satisfied, cert is made containing ID info, public key, etc.
  • CA then digitally signs the cert with their private key
82
Q

CPS

A

Certificate Practice Statement

How CA is structured
How certs will be managed
How subscriber's ID is validated
How to request revocation
Which standards and protocols are used
83
Q

OCSP

A

Online Certificate Status Protocol

  • Checks for revoked certs
  • Queries a CA or RA that maintains a list of expired certs
  • Server sends a response with status of valid, suspended or revoked
84
Q

CRL

A

Certificate Revocation List

IDs revoked certs
Expired certs not on on the CRL

85
Q

Certificate Suspension

A

Certs can be suspended
Ensures key is unusable for a period of time
Suspend rather than expire to make them TEMPORARILY invalid

86
Q

Certificate Expiration

A

If a cert expires, a new cert must be issued

NOT added to the CRL

87
Q

Certificate Renewal

A

Unexpired certs can be renewed close to the end of the expiring cert’s lifetime

Allows same cert to be used past the original expiry time

Not a good practice

88
Q

Certificate Destruction

A

Establish policies for destroying old keys
When key/cert no longer useful, destroy and remove from system
When destroyed, notify CA so CRL and OCSP can be updated
Deregistration should occur when a key is destroyed

89
Q

Trust Models (4):

A

Single-Authority (AKA third-party trust)
Hierarchical Trust
Bridge Trust
Web of Trust (AKA peer-to-peer)

90
Q

Single Authority

A

Third party signs key/cert
User trusts authority and all keys issued by them
Trust verified by digital sig attached to public key

91
Q

Hierarchical Trust

A

Root CA>Intermediate CA>Leaf CA

92
Q

Bridge Trust

A

Trust between Root CAs

93
Q

Web of Trust

A

All parties involved trust each other

CA does not exist to certify owners

94
Q

Centralized Key Management

A

Central entity in charge or issuing keys

CA keeps a copy of the key

95
Q

Decentralized Key Management

A

End user generates their own key

Does not provide key escrow (no key recovery)

96
Q

Two Methods for Key Storage

A

Software-based:

  • Access violations/intrusions
  • Easily destroyed
  • Subject to security of access control system

Hardware-based:

  • Most secure
  • More expensive
  • Relies on physical security
  • Smart cards/flash drives
97
Q

Key Escrow

A

Third party may gain access to key storage
Allows for key recovery
Key’s must be secured on escrow network/systems

98
Q

Recovery Agent

A

Someone with authority to remove keys from escrow

99
Q

M of N Control

A

Requires two or more recovery agents
Must but multiple key escrow recovery agents
Minimum number of agents must work to recover key

100
Q

Revoking Keys

A

Conducted when:

  • Keys compromised
  • Authentication process malfunction
  • People transferred/fired
  • Other security risks occur

Keeps key from being misused

101
Q

Suspending Keys

A

Temporary

Unusable for a period of time

102
Q

Renewing Keys

A

Enable key for use after scheduled expiry
Reissued for certain time
Bad practice

103
Q

TPM

A

Trusted Platform Module

Hardware
Stream Cipher Encryption
Symmetric

Sec Plus (5 decks)

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