What Is PKCS5Padding?
This section describes what is PKCS5Padding - a schema to pad cleartext to be multiples of 8-byte blocks.
As you can see from previous tutorials, DES algorithm requires that the input data to be 8-byte blocks.
If you want to encrypt a text message that is not multiples of 8-byte blocks, the text message must be
padded with additional bytes to make the text message to be multiples of 8-byte blocks.
PKCS5Padding is a padding scheme described in: RSA Laboratories,
"PKCS #5: Password-Based Encryption Standard,"
version 1.5, November 1993.
PKCS5Padding schema is actually very simple. It follows the following rules:
- The number of bytes to be padded equals to "8 - numberOfBytes(clearText) mod 8".
So 1 to 8 bytes will be padded to the clear text data depending on the length of the clear text data.
- All padded bytes have the same value - the number of bytes padded.
PKCS5Padding schema can also be explained with the diagram below, if M is the original clear text
and PM is the padded clear text:
If numberOfBytes(clearText) mod 8 == 7, PM = M + 0x01
If numberOfBytes(clearText) mod 8 == 6, PM = M + 0x0202
If numberOfBytes(clearText) mod 8 == 5, PM = M + 0x030303
If numberOfBytes(clearText) mod 8 == 0, PM = M + 0x0808080808080808
Table of Contents
About This Book
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 Java Implementation in JDK by Sun
Steps of Using DES Algorithm in JDK JCE
Testing DES Algorithm in JDK JCE
►What Is PKCS5Padding?
JceSunDesPaddingTest.java - JCE DES Padding Test
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
Using Certificates in Google Chrome
Using Certificates in Firefox
Full Version in PDF/EPUB