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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