**Cryptography Tutorials - Herong's Tutorial Examples** - Version 5.33, by Dr. Herong Yang

DES Encryption Operation Mode Introduction

This section describes what are DES encryption operation modes and notations used to describe how each operation mode works.

DES encryption algorithm defines how a single 64-bit plaintext block can be encrypted. It does not define how a real plaintext message with an arbitrary number of bytes should be padded and arranged into 64-bit input blocks for the encryption process. It does not define how one input block should be coupled with other blocks from the same original plaintext message to improve the encryption strength.

(FIPS) Federal Information Processing Standards Publication 81 published in 1980 provided the following block encryption operation modes to address how blocks of the same plaintext message should be coupled:

- ECB - Electronic Code Book operation mode.
- CBC - Cipher Block Chaining operation mode.
- CFB - Cipher Feedback operation mode
- OFB - Output Feedback operation mode

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

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.

Ek(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.

With these notations, we are ready to describe different operation modes that can be applied the DES encryption algorithm.

Table of Contents

Introduction to AES (Advanced Encryption Standard)

DES Algorithm - Illustrated with Java Programs

DES Algorithm Java Implementation

DES Algorithm - Java Implementation in JDK JCE

►DES Encryption Operation Modes

►DES Encryption Operation Mode Introduction

What is ECB (Electronic CodeBook) Operation Mode?

What is CBC (Cipher Block Chaining) Operation Mode?

What is CFB (Cipher FeedBack) Operation Mode?

What is OFB (Output FeedBack) Operation Mode?

JCE DES Operation Mode Testing Program

JCE DES Operation Mode Testing Program Result

PHP Implementation of DES - mcrypt

Blowfish - 8-Byte Block Cipher

Secret Key Generation and Management

Cipher - Secret Key Encryption and Decryption

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

OpenSSL Introduction and Installation

OpenSSL Generating and Managing RSA Keys

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)