Cryptographic Systems

Cryptographic Systems

1. Services

   • Securing Communications
     • Authentication
       • authentication
       • data nonrepudiation services
     • Data Integrity
     • Data Confidentiality
       • encrypted text
       • ciphertext
   • Cryptography
     • history
       • Scytale
       • Caesar Cipher
       • Vigenère Cipher
       • Enigma Machine
     • Transposition
       • they are simply rearranged
     • Substitution
       • substitute one letter for another.
       • polyalphabetic
       • monoalphabetic
     • One-time pad
       • AT&T Bell Labs
   • Cryptanalysis
     • Methods
       • Brute-force method
       • Ciphertext method
   • Cryptology
     • Cryptography
       • it is believed that cryptographers are in the lead
     • Cryptanalysis
       • , it is actually a necessity

2. Confidentiality

   • Encryption
     • Symmetric algorithms
       • pre-shared key
       • By obtaining the key, anyone can encrypt and decrypt messages.
     • Asymmetric algorithms
       • different keys
     • Block Ciphers
       • 64 bits or 128 bits
     • Stream Ciphers
       • Vigenère
   • Data Encryption Standard

3. Public Key

4. Basic Integrity and Authenticity

   • Integridad con MD5, SHA-1 y SHA-2
     • Secure Hash Algorithm
       • NIST published four additional hash functions in the SHA family
     • Message Digest 5 Algorithm
       • exclusive OR
       • replaced with a stronger algorithm such as SHA-2
   • Cryptographic Hashes
     • Function Properties
       • The input can be any length. The output has a fixed length.
     • Function
       • message digest
       • message
     • Two well-known hash functions
       • MD5 with 128-bit digest
       • SHA-256 with 256-bit digest
   • Authenticity with HMAC
     • HMAC Operation
     • Keyed-Hash
       • secret keys
       • HMAC

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