What Is Block Cipher?

This section describes what is block cipher - An encryption scheme in which 'the clear text is broken up into blocks of fixed length, and encrypted one block at a time'.

Block Cipher - An encryption scheme in which "the clear text is broken up into blocks of fixed length, and encrypted one block at a time".

Usually, a block cipher encrypts a block of clear text into a block of cipher text of the same length. In this case, a block cipher can be viewed as a simple substitute cipher with character size equal to the block size.

ECB Operation Mode - Blocks of clear text are encrypted independently. ECB stands for Electronic Code Book. Main properties of this mode:

CBC Operation Mode - The previous cipher text block is XORed with the clear text block before applying the encryption mapping. Main properties of this mode:

Product Cipher - An encryption scheme that "uses multiple ciphers in which the cipher text of one cipher is used as the clear text of the next cipher". Usually, substitution ciphers and transposition ciphers are used alternatively to construct a product cipher.

Iterated Block Cipher - A block cipher that "iterates a fixed number of times of another block cipher, called round function, with a different key, called round key, for each iteration".

Feistel Cipher - An iterate block cipher that uses the following algorithm:

Input: 
   T: 2t bits of clear text
   k1, k2, ..., kr: r round keys
   f: a block cipher with bock size of t
   
Output: 
   C: 2t bits of cipher text

Algorithm: 
   (L0, R0) = T, dividing T in two t-bit parts 
   (L1, R1) = (R0, L0 ^ f(R0, k1))
   (L2, R2) = (R1, L1 ^ f(R1, k2))
   ......
   C = (Rr, Lr), swapping the two parts

^ is the XOR operation.

DES Cipher - A 16-round Feistel cipher with block size of 64 bits. DES stands for Data Encryption Standard.

Table of Contents

 About This Book

 Cryptography Terminology

 Cryptography Basic Concepts

 Introduction to AES (Advanced Encryption Standard)

Introduction to DES Algorithm

What Is Block Cipher?

 DES (Data Encryption Standard) Cipher Algorithm

 DES Key Schedule (Round Keys Generation) Algorithm

 DES Decryption Algorithm

 DES Algorithm - Illustrated with Java Programs

 DES Algorithm Java Implementation

 DES Algorithm - Java Implementation in JDK JCE

 DES Encryption Operation Modes

 DES in Stream Cipher Modes

 PHP Implementation of DES - mcrypt

 Blowfish - 8-Byte Block Cipher

 Secret Key Generation and Management

 Cipher - Secret Key Encryption and Decryption

 Introduction of RSA Algorithm

 RSA Implementation using java.math.BigInteger Class

 Introduction of DSA (Digital Signature Algorithm)

 Java Default Implementation of DSA

 Private key and Public Key Pair Generation

 PKCS#8/X.509 Private/Public Encoding Standards

 Cipher - Public Key Encryption and Decryption

 MD5 Mesasge Digest Algorithm

 SHA1 Mesasge Digest Algorithm

 OpenSSL Introduction and Installation

 OpenSSL Generating and Managing RSA Keys

 OpenSSL Managing Certificates

 OpenSSL Generating and Signing CSR

 OpenSSL Validating Certificate Path

 "keytool" and "keystore" from JDK

 "OpenSSL" Signing CSR Generated by "keytool"

 Migrating Keys from "keystore" to "OpenSSL" Key Files

 Certificate X.509 Standard and DER/PEM Formats

 Migrating Keys from "OpenSSL" Key Files to "keystore"

 Using Certificates in IE (Internet Explorer)

 Using Certificates in Firefox

 Using Certificates in Google Chrome

 Outdated Tutorials

 References

 PDF Printing Version