Cryptography

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Cryptography is the science and practice of altering data to make it unintelligible to unauthorized parties.

• literally means “secret writing”
• does not matter if third parties know of the existence and location of the secret
  • can never understand what it is without the means to decode it
• opposite of security through obscurity
  • means keeping something a secret by hiding it
  • considered impossible (or at least high risk) on a computer system

Terminology

• Cryptography refers specifically to the use and practice of cryptographic techniques.
• Cryptanalysis refers to the study of vulnerabilities (theoretical or practical) in cryptographic algorithms and systems and the use of exploits against those vulnerabilities to break such systems
• Cryptology refers to the combined study of cryptography (secret writing) and cryptanalysis.
• Cryptolinguistics refers to translating between human languages to produce useful information, insight, or actionable intelligence (has little to do with cryptography)
• Plaintext is unencrypted message/data.
  • aka cleartext
• Ciphertext is encrypted message/data.
• Algorithm is the operations performed to encrypt and decrypt data.
  • aka cipher

Types

• two types of cryptographic cipher or algorithm:
  • Encryption
    • converts a human-readable plaintext into ciphertext
    • further broken down into symmetric and asymmetric encryption
  • Cryptographic Hash
    • converts a variable length string into a fixed-length hash
    • cannot be converted back to plaintext
    • can prove integrity of data

Uses

• different cryptographic solutions are used to protect each data state

Discussing Cryptographic Examples

• it is customary to use a cast of characters to describe different actors involved in the process of an attack against encryption systems:
  • Alice
    • sender of a genuine message
  • Bob
    • intended recipient of the message
  • Mallory
    • a malicious attack attempting to subvert the message