Cryptographic Systems

Cryptographic Systems

1. Securing Communications

   • objectives
     • Authentication
       • protocols
         • hash message
         • authentication code (HMAC)
       • methods
         • authentication services
         • data nonrepudiation services
     • Integrity
       • MD5
       • SHA
     • Confidentiality
       • symmetric encryption
       • Data Encryption Standard (DES)
       • 3DES
       • Advanced Encryption Standard (AES)

2. Cryptography

   • methods
     • Transposition Ciphers
       • FLANK EAST ATTACK AT DAWN -> NWAD TAKCATTA TSAE KNALF
       • DES and the 3DES
     • Substitution Ciphers
       • substitute one letter for another
         • A is 1 , B is 2 ...
     • One-Time Pad Ciphers
       • teletype cipher in which a prepared key consisting of an arbitrarily long
       • RC4

3. Cryptanalysis

   • Brute-force method
   • Ciphertext method
   • Known-Plaintext method
   • Chosen-Plaintext method
   • Chosen-Ciphertext method
   • Meet-in-the-Middle method

4. Cryptology

5. Basic Integrity and Authenticity

   • Cryptographic Hashes
     • Function
       • verify and ensure data integrity.
     • used in
       • symmetric secret authentication key
       • one-time and one-way responses
       • check proof, such as those used in digitally signed contracts
     • Properties
       • h= H(x).
         • H takes an input
         • x and returns a fixed-size
         • string called the hash value h.
     • methods
       • Message Digest 5 Algorithm
         • compute a hash from the given input data
       • Secure Hash Algorithm
         • takes a message of less than 2^64 bits in length and produces a 160-bit message digest
     • Authentication
       • (HMAC or KHMAC)
         • is a type of message authentication code (MAC
   • Key Management
     • key generation
     • key verification
     • key exchange
     • kay storage
     • key lifetime
     • key revocation and destruction
     • Key Length and Keyspace
       • Key length
         • his is the measure in bits.
       • Keyspace
         • is the number of possibilities that can be generated
     • Types
       • Symmetric keys
       • Asymmetric keys
       • Digital signatures
       • Hash keys

6. Confidentiality

   • Encryption
     • Symmetric Encryption
     • Symmetric Block Ciphers and Stream Ciphers
       • transform a fixed-length block of plaintext into a common block
       • tream ciphers encrypt plaintext one byte or one bit at a time
     • DES Symmetric Encryption
       • DES has a fixed key length
       • A DES key is always 56 bits long
     • Standard
       • 3DES Operation