Cryptography and Password Cracking
1. Classification
Classification of algorithms:
Based on Cryptography
Symmetric Cryptography (DES/3DES, AES. RC4, Blowfish, Caesar's, etc.) Both sender and receiver share the same key
Public-Key / Asymmetric Cryptography Sender and receiver uses different keys, public-key (for encrypting) and private-key (for decrypting).
When a message is encrypted using Bob's public key, only Bob's private key will be able to decrypt the message.
Public and private key are mathematically derived from prime number's however private key cannot be derived from public key. It is based on the factorization mathematical problem (harder to find a factor of something than to create a number by multiplying its factors).
Based on How Plaintext in Handled
Block Cipher (DES, AES, etc.) Data is handled in blocks (say chunks of 8 bytes)
Simple block ciphers can be used din a number of modes, we will explain 2 very basis modes:
ECB (Electronic Code Book) In this mode, the message is divided into blocks and each block is encrypted separately.
This makes ciphertext analysis much easier because identical plaintext blocks are encrypted into identical ciphertext blocks.
This mode is deprecated
CBC (Cipher Block Chaining) In this mode, each ciphertext block is derived from the previous block as well. An initialization vector is used for the first block.
Stream Cipher (RC4, A5/1, etc.) Data is handled 1 byte at a time
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