Q1. What is cryptography?
Ans : Cryptographic systems are generally classified along 3 independent dimensions :
Type of operations used for transforming plain text to cipher text
All the encryption algorithms are based on two general principles: substitution, in which each element in the plaintext is mapped into another element, and transposition, in which elements in the plaintext are rearranged.
The number of keys used are:
1. If the sender and receiver uses same key then it is said to be symmetric key (or) single key (or) conventional encryption.
2. If the sender and receiver use different keys then it is said to be public key encryption.
Cryptography & Network Security AKTU Note
Page Length : 228
Introduction to security attacks, services and mechanism, introduction to cryptography.
- Conventional Encryption : Conventional encryption model, classical encryption techniques- substitution ciphers and transposition ciphers, cryptanalysis, stereography, stream and block ciphers.
- Modern Block Ciphers : Block ciphers principals, Shannon’s theory of confusion and diffusion, fiestal structure, data encryption standard(DES), strength of DES, differential and linear crypt analysis of DES, block cipher modes of operations, triple DES, IDEA encryption and decryption, strength of IDEA, confidentiality using conventional encryption, traffic confidentiality, key distribution, random number generation.