Cryptography Tutorials - Herong's Tutorial Examples - v5.42, by Herong Yang
What is CFB (Cipher FeedBack) Operation Mode?
This section describes what is CFB (Cipher FeedBack) Operation Mode - each plaintext block is XORed with the encrypted version of the ciphertext of the previous block to be the ciphertext block.
CFB (Cipher FeedBack) operation mode can be described with notations defined earlier as the following formula and diagram:
C[i] = P[i] XOR Ek(C[i-1]) C = P XOR Ek(IV) IV | -----| -----| Ek() / Ek() / Ek() | / | / | | / | / | P--XOR / P--XOR / P--XOR | / | / | | / | / | C C C
As you can see from the formula and the diagram, in CFB mode, each block of plaintext is XORed with the encrypted version of the previous ciphertext to generate the current ciphertext block. In this way, each ciphertext block is depending on all plaintext blocks up to that point. Note that for the first block, the Initial Vector (IV) is used as the previous ciphertext block.
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 Google Chrome