Cryptography Tutorials - Herong's Tutorial Examples - Version 5.21, by Dr. Herong Yang

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 Terminology

 Cryptography Basic Concepts

 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 (Internet Explorer)

 Using Certificates in Firefox

 Using Certificates in Google Chrome

 Outdated Tutorials

 References

 Printable Copy - PDF Version

What Is PKCS5Padding? - Updated in 2014, by Dr. Herong Yang