- Cryptography Tutorial
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- Origin of Cryptography
- Modern Cryptography
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- Traditional Ciphers
- Modern Symmetric Key Encryption
- Block Cipher
- Feistel Block Cipher
- Data Encryption Standard
- Triple DES
- Advanced Encryption Standard
- Block Cipher Modes of Operation
- Public Key Encryption
- Data Integrity in Cryptography
- Cryptography Hash functions
- Message Authentication
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Modern Symmetric Key Encryption
Digital data is represented in strings of binary digits (bits) unlike alphabets. Modern cryptosystems need to process this binary strings to convert in to another binary string. Based on how these binary strings are processed, a symmetric encryption schemes can be classified in to −
Block Ciphers
In this scheme, the plain binary text is processed in blocks (groups) of bits at a time; i.e. a block of plaintext bits is selected, a series of operations is performed on this block to generate a block of ciphertext bits. The number of bits in a block is fixed. For example, the schemes DES and AES have block sizes of 64 and 128, respectively.
Stream Ciphers
In this scheme, the plaintext is processed one bit at a time i.e. one bit of plaintext is taken, and a series of operations is performed on it to generate one bit of ciphertext. Technically, stream ciphers are block ciphers with a block size of one bit.
