Cryptography

• Brute Force Attack


  Systematically guessing potential keys until the correct key is found
• Cryptanalysis


  The science of breaking cryptography
• Authentication

  The process of verifying the identity of a user
• Data Breach


  Leak of sensitive data to a third party or unauthorised deletion of personal information
• Cybersecurity 


  The protection of information systems, data, and online services from unauthorised access, harm or misuse
• Availability

  The security objective of ensuring timely and uninterrupted access to and use of information
• Confidentiality 


  The security objective to preserve authorised restrictions on information access and disclosure
• Non-repudiation 


  Sender is provided proof of delivery and recipients proof of sender's identity - nether can deny their communication
• Substitution encryption is a bijective function


  Each ciphertext letter has only one plaintext corresponding letter
• Key Space of a Cipher


  All possible combinations of keys
• GSM Technology 


  Achieves confidentiality through a stream-cipher
• Letter Frequency


  The number of times letters of the alphabet appear on average in written language
• Polyalphabetic Cipher (Vigenère Cipher)


  Works by using a repeating keystream
• Stream Ciphers


  Perform encryption bit-by-bit and are used for streaming applications such as voice or video transmission
• Block Ciphers


  Operates on blocks or chunks of text and the plaintext is divided into blocks or chunks of text too
• A5/1 Stream Cipher


  This is one of the encryption algorithms used in cybersecurity for GSM. It uses the modulo-2 arithmetic.
• The modulo-2 addition operator


  Is essentially the XOR operator
• True Random Number Generators (TRNG)


  Randomness from a real random phenomenon
• Pseudo Random Number Generators (PRNG)


  Are computed, seem random but are deterministic
• Cryptographically Secure Random Number Generators (C-RNG)


  PRNG with one additional property - the numbers are unpredictable
• One-Time Pad (OTP)


  The OTP is a stream cipher where the key stream bits stem from TRGN and each key stream bit is only used once
• OTP Advantage


  Knowing the ciphertext doesn't give you any additional insight into the value on the plaintext
• OTP Disadvantage

  Keys need to be as long as the message and because keys cannot be reused that's a lot of bits over time
• Kerckhoff's Principle


  A cryptosystem should be secure even if the attacker knows all details about the system except the secret key
• Cryptography


  The science of creating secret messages
• Cryptanalysis


  The science of breaking cryptographic systems and deciphering secret messages
• Encryption


  Hiding a message by using a coder or cipher
• Decryption


  Revealing an encrypted message
• Plaintext


  The original message before encryption
• Ciphertext


  The encrypted message
• Data Integrity


  Information and programs are only changed specifically
• System Integrity


  System performs operation in an unimpaired way
• Authenticity


  Being genuine and being able to be verified and trusted
• Accountability


  Will be able to be traced back to a specific person
• Methods of Confidentiality


  Information classification, access controls, encryption, governance
• Integrity


  Guarding against improper information modification or destruction
• Identification


  The process of verifying the claimed identity of a user attempting to access a computer system