Cryptology

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Underlying principles

• Information theory [r]: Theory of the probability of transmission of messages with specified accuracy when the bits of information constituting the messages are subject, with certain probabilities, to transmission failure, distortion, and accidental additions. ^[e]
• Random number [r]: A member of a sequence of which the successive values cannot be predicted, produced by measurement of physical phenomena, appropriate algorithms, or a combination of the two ^[e]
• Statistical characteristics of language
• Computationally intractable problems

Methods of proving information is correct or has been transferred

Authentication

Sender authentication

Key management

• Public Key Infrastructure [r]: Add brief definition or description
• Pretty Good Privacy [r]: E-mail encryption package created by Phillip Zimmerman. ^[e]

Methods of concealing information

Cryptography

• Ciphers and codes, including basic methods
• Symmetric, asymmetric, and both
• Key management protocols

Specific cipher implementations

Manual

• Monoalphabetic substitutions
• Polyalphabetic substitutions
  • Straddling methods
• Transposition
• Superencipherment

Mechanical/Electromechanical

• Jefferson/Bazeries cylinder, strip ciphers
• Vernam
• Rotor and rotor-like: Hagelin, Enigma, Purple, SIGABA/Typex

Computer (general purpose and chip) implementations

• General characteristics of military (KG vs KW, etc.)
• Non-text/data: secure voice, video, fax
• DES
• PGP
• AES

Steganography

• Invisible ink methods?
• Classic covert channel
• Masking with graphics
• Spread spectrum, frequency agility, {{seealso|electronic warfare))

Methods of obtaining partial or full information

See also: communications intelligence for things including traffic analysis and direction finding

• Man-in-the-middle attack
• Various general scenarios: brute force, chosen plaintext
• Basic mathematical cryptanalysis: frequency analysis, index of coincidence, Kappa test
• Advanced mathematical cryptanalysis
• Red/black engineering and other COMSEC supporting measures

See also: communications intelligence

• "Practical cryptanalysis" (black bag job), radiofrequency MASINT#Unintentional Radiation MASINT (TEMPEST/Van Eck, etc.), acoustic cryptanalysis
• "rubber hose cryptanalysis"
  • "This is the most powerful handgun in the world. I can't remember if I've fired five or six times. Feeling lucky, punk?" This is an example of quantum cryptanalysis, with the .44 Magnum chamber is loaded or not loaded, but Heisenberg requires one pull the trigger to find out.