Cryptography

Cryptography

1. Fundamentals of cryptography

   • Non-repudiation
     • Prevents an entity from denying its participation in a transaction or communication.
   • Confidentiality
     • Ensures that only authorized individuals can access the information.
   • Integrity
     • Guarantees that the information has not been altered during its transmission or storage
   • Authenticity
     • Allows verifying the identity of the parties involved in communication or a transaction.

2. History of Cryptography

   • Middle Ages
     • Transposition and Substitution Ciphers: During the Middle Ages, more complex ciphers were developed, such as the Vigenère cipher and the Alberti cipher, which combined transposition and substitution.
   • 20th Century
     • Enigma Machines: During World War II, the German Enigma machine represented a significant advance in cryptography.
   • Digital Era
     • Public Key Cryptography: In the 1970s, public key cryptography was developed, revolutionizing computer security. Whitfield Diffie and Martin Hellman proposed public key exchange to establish secure communication.
   • Ancient Times
     • Classic Ciphers: Ancient Egyptians used simple encryption systems.

3. Cryptographic Algorithms

   • Symmetric Encryption
     • AES (Advanced Encryption Standard): Widely used for symmetric encryption, AES replaced the Data Encryption Standard (DES) and provides increased security.
       • RC2/RC4-RC5
       • IDEA
       • BLOWFISH/ TWOFISH
       • DES/3DES
       • AES
   • Asymmetric Encryption
     • RSA (Rivest, Shamir, Adleman): One of the earliest public key algorithms, used for both encryption and digital signatures
       • DSA
       • ELGAMAL
   • Hash Functions
     • SHA-256 (Secure Hash Algorithm): Produces a 256-bit hash value and is used to ensure data integrity
       • MD5
       • ROPE-MD
       • SHA1

4. Examples of Applications

   • SSL/TLS (Transport Layer Security)
     • Uses cryptography to ensure the security of communications on the Internet, such as in online banking transactions.
   • PGP (Pretty Good Privacy
     • Employs public key cryptography and hash functions for securing email communication
   • Blockchain
     • Utilizes hash functions and public key cryptography to ensure the integrity and authenticity of transactions in cryptocurrencies like Bitcoin and Ethereum

5. Cryptography is the study of techniques and algorithms to protect communication and information against unauthorized third parties.