Domain 3: Security Engineering
Study Notes
Cryptography
Real-World Demo of Symmetric Key Encryption
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Associate These Terms With Cryptography
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Confidentiality, integrity, nonrepudiation, digital signatures, authentication, IPSec, VPNs, SSL, TLS
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Historical Cryptography Stuff
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Caesar Substitution, Scytale, Enigma
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Symmetric Key Encryption | noitpyrcnE yeK cirtemmyS
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Types of Symmetric Key Block Ciphers
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DES
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For DES, remember it has a 64-bit cipher, but only a 56-bit key length is used. The other 8 bits are for parity.
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DES also has 16 rounds of substitution and transposition
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DES Modes: ECB, CBC, CFB, OFB, CTR
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FYI: Block ciphers use confusion and diffusion
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AES
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AES-256 is the STRONGEST encryption method for the CISSP exam!
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Key size cipher rounds: 128-bit, 192-bit, 256-bit
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Uses substitution, shift row, column mixing
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Other types of block ciphers
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3DES, AES, RC6, Blowfish, Twofish, Skipjack, IDEA
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Why Do We Use Cryptography?
Where Do We Use Cryptography?
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Public Key Infrastructure (PKI)
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Think public/private keys
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HTTPS/SSL
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Cryptographic ciphers are exchanged after the TCP Handshake and during the SSL Handshake
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SSH
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SSH is the more secure version of Telnet as it uses public/private keys
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PGP
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We use asymmetric encryption when using PGP for email
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IPSec VPN
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Cryptography is used heavily in IPSec VPNs to create an encrypted tunnel that is near impossible to break
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For Confidentiality
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Unauthorized persons cannot see or decode the data unless they have a private key, symmetric key, or session key
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For Integrity
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Unauthorized persons cannot change the data
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Authorized persons cannot accidentally change the data
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Availability?
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In terms of availability, it is not associated with cryptography that much. Sure, data at rest is encrypted, but when it comes to the CISSP, availability is not usually associated with cryptography
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Authentication
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Verifies the identity of a person or subject
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This includes people, processes, and systems
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Important note: authentication is NOT a part of the CIA Triad
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Non-repudiation
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A technique of confirming the original sender
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Disallows the sender to deny they sent a message
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Important when it comes to accountability, logging, and auditing
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Cryptography Terms and Definitions
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Cryptosystem
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Everything you basically need to implement encryption
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You'll pick some method to generate a key
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One key will enrypt
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One key will decrypt
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Plaintext or cleartext
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Data before it is encrypted
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Example "Meet me at 3PM"
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Ciphertext
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Data after it is encrypted
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Example "@:L#jk09'PFIJ093jf"
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Algorithm
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The mathmatical calculations required to turn plaintext into ciphertext
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Encrypt
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Change from plaintext to ciphertext
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Decrypt
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Change from ciphertext to plaintext
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Work factor
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The amount of time it takes to break an algorithm
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The amount of time it takes to figure out an encryption key
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Key
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For each algorithm used, there is a key
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The keys are the ones that make each ciphertext unique
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The keys to an algorithm is what hackers will try to get
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Can be symmetric or asymmetric
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Each key should ALWAYS generate a different set of ciphertext if used on the same plaintext
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Keyspace
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The amount of 1's and 0's that can be used to create a key
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Key clustering
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When the same ciphertext is generated from the same plaintext
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This is NOT good
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You want every key to have a unique ciphertext output
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Initialization Vector
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Sometimes patterns are created if the same keyspace or keys are used over and over again.
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An IV injects a small random number to eliminate any patterns
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Used in DES-CBC mode
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Salt
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Kind of like an initialization vector
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Used for increasing the randomness and unpredictability of ciphertext
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Fields of Cryptography
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Cryptography
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graphy means writing
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It means the science of coming up with difference types of super strong algorithms
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Cryptanalysis
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analysis means analysis
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It is the art of breaking the algorithms created in cryptography
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The NSA employs cryptanalyst to help break encryption ciphers to decode messages
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Cryptology
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logy means reading
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It is the study of both cryptography and cryptanalysis
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The study of creating encryption ciphers, and the study of breaking encryption ciphers
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