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Symmetric cryptography in Java

Introduction

As you know data security is a significant aspect of any enterprise application. Starting from password encryption to any data exchange, cryptography has been in use for all kinds of purpose. However there are two kinds of cryptography, one is symmetric and another is asymmetric. In case of symmetric cryptography, a secret key is used for all kinds of encryption and decryption. This secret key is shared by all the members who want to participate in the encryption and decryption process. There are several algorithms for the symmetric cryptography. DES( Data Encryption Standard) is one of them. In case of normal login screen of web based application, implementation of DES algorithm is used for password encryption.

Technicalities

Java cryptography provides suitable and flexible framework for the use of symmetric cryptography. DES algorithm is commonly known as symmetric algorithm. In case of symmetric cryptography, the secret key is used in a plain text file and this file is shared between the members. This file is used to retrieve the secret key for all kinds of encryption and decryption. In this regards I can provide you an example that think of a situation where the two lovers receive their love letters in encrypted format so that no body can read it. They have a common key called the DES secret key. They use the secret key to decrypt the contents of the encrypted love letters at their end. It means that the secret key is generated once and shared between the members. For more details of DES algorithm please refer to the java docs and JCE framework provided by Sun. In this article I will provide an example of how to use the implementation of DES algorithm.

Complete example

The following is the utility class for the cryptography management. The class name is

“KeyUtil.java”.

package com.dds.core;

import java.io.FileInputStream;

import java.io.FileOutputStream;

import java.io.InputStream;

import java.io.OutputStream;

import javax.crypto.Cipher;

import javax.crypto.CipherInputStream;

import javax.crypto.CipherOutputStream;

import javax.crypto.KeyGenerator;

import javax.crypto.SecretKey;

import javax.crypto.spec.SecretKeySpec;

/**This is a utility class for all kinds

* of useful methods related to symmetric

* cryptography. This class only provides

* the use of DES algorithm.You can use any

* other symmetric algorithm similarly.

* @author Debadatta Mishra( PIKU )

The above class provides several useful methods for encryption and decryption. Please refer the java docs provided for each method. Generally in many applications, you may have to use either for a file or for a String. In the above class , I have provided two methods for file encryption and decryption. In certain situation, it is required that you have to encrypt the contents of the file. More specifically I can provide you an example, think about a file called “sample.txt”. You have to encrypt the contents of the file “Sample.txt” so that after encryption when you are opening the file, it becomes unreadable. It may also be required to transfer the file to network. Sometime a requirement comes that there is file called “Sample.txt”, you have to encrypt the contents of the file and to create a new file called “Sample_en.txt”. In this case you have two files, one is the original one as well as the encrypted file. Now refer to the following subordinate classes for the use.

Class name: KeyGenerator.java

package com.dds.core;

import java.io.File;

import java.io.FileOutputStream;

import java.io.OutputStream;

import java.util.Properties;

* This class is used to generate the secrete key and

* stores the secret key in a file called secret.key.

* @author Debadatta Mishra(PIKU)

public class KeyGenerator {

*This method is used to obtain the

* path of the file secret.key.

* @return path of Key

The above class provides several ways you can encrypt and decrypt the file.

Please follow the following sequence to execute the above classes.

Conclusion

I hope that you will enjoy my article for the symmetric cryptography. For asymmetric cryptography please refer to the link http://www.articlesbase.com/information-technology-articles/asymmetric-cryptography-in-java-438155.html. If you find any problems or errors, please feel free to send me a mail in the address debadattamishra@aol.com . This article is only meant for those who are new to java development. This article does not bear any commercial significance. Please provide me the feedback about this article.