Introducting DES Stream Cipher Modes

This section describes what are DES encryption stream cipher modes and how CFB and OFB block operation modes can be modified as stream modes.

As we know from previous tutorials, DES algorithm is a block cipher algorithm. But it can be operated in different ways to become stream ciphers.

(FIPS 81) Federal Information Processing Standards Publication 81 published in 1980 defined the following 4 operation modes:

See http://www.itl.nist.gov/fipspubs/fip81.htm for details.

In FIPS 81, the last two operation modes, CFB and OFB, are defined in ways so that they can be used as stream ciphers.

In order to describe these operation modes, we need to define the following notations:

P = P[1], P[2], P[3], ..., P[i], ... - Representing the original plaintext message, P, being arranged into multiple 64-bit plaintext blocks. P[i] represents plaintext block number i.

E(P[i]) - Representing the DES encryption algorithm applied on a single 64-bit plaintext block, P[i], with a predefined key, k.

C = C[1], C[2], C[3], ..., C[i], ... - Representing the final ciphertext message, C, being regrouped from multiple 64-bit ciphertext blocks. C[i] represents ciphertext block number i.

IV - Called "Initial Vector", representing a predefined 64-bit initial value.

Table of Contents

 About This Book

 Cryptography Terminology

 Cryptography Basic Concepts

 Introduction to AES (Advanced Encryption Standard)

 Introduction to DES 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

Introducting DES Stream Cipher Modes

 CFB (Cipher FeedBack) as a Stream Cipher

 OFB (Output FeedBack) as a Stream Cipher

 CFB and OFB Stream Ciphers Implemented in JCE

 JCE DES Stream Ciphers Testing Program

 JCE DES Stream Ciphers Testing Program Result

 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