ZIP and UNZIP with password in JAVA

ZIP and UNZIP with password in JAVA – A Pragmatic approach by Debadatta Mishra
Introduction
Zip and Unzip is a very common activity for a computer user. A user normally uses zip utility to compress a directory to create a zip file . There are many ready-made softwares like winzip,7zip,winrar etc are available to achieve this. However it is also possible to protect the zip file with a password so that end user has to provide the password to unzip the zip file. This is the very common scenario which can be achieved by zip utility tool. The significant part of my article is to provide you the solution to achieve this using java program. While developing project you may encounter a scenario that you have to create a password protected zip file that can be unzipped by any zip tool like winzip. Let me explain a complete scenario for your understanding.

In a system, some files are generated for a user and all the files are zipped with a password. The generated password protected zip file is sent to the user through email and the password for the zip file to open is sent to the particular user as an SMS to the user’s mobile. Similarly the end-user creates a password protected zip file and uploads to a online system with the user’s password in a text field. In this case we have to develop a system where the system will be able to create a password protected zip file and should be able to extract all the files from a password protected zip file. Let me show you how you can achieve it.

Technicalities
However Java provides the feature of creating a zip file and also provides the feature to unzip or decompress a zip file. But there is no default java API to create a password protected zip file and also there is no default java API to unzip a password protected zip file. To facilitate this feature of zip utility some developers have developed java API in this regard. We have to use their API to achieve this. We have to look into the following aspects of zip utility.

1.Java enabled system should be able to generate a password protected zip file and that password protected zip file can be unzipped by any zip utility like winzip and others.
2.Java enabled system should be able to decompress or unzip a password protected zip file created by any zip utility like winzip and others.

The followings are the API you have to use for this objective.

1.To create a password protected zip file in java, you have to use “winzipaes”. It is avilable in Google code. You can download the .jar file and the source code from the following link.

http://code.google.com/p/winzipaes/
This API helps to add a password to a already created zip file. It means that if you want to create a password protected zip file, first you have to create a zip file and then you can add a password that zip file. It is a pure java API works with any operating system. You have to download the following jar file from the above URL.

passwordcompressor.jar

2.To unzip or decompress a password protected zip file, you have to use “sevenzipjbind”. It is available in sourceforge.net site. You can download the .jar files from the following link.

http://sourceforge.net/projects/sevenzipjbind/files/ This API helps to extract all the files and folders from password protected zip file created by any zip utility tool. You have to download the following .jar files from the above URL.

sevenzipjbinding-AllPlatforms.jar
sevenzipjbinding.jar

3.For password protection, you have to use Bouncecastle cryptographic API. You can download the .jar file from the following link.
http://www.bouncycastle.org/
You have to download the following .jar files from the above URL.
bcprov-jdk15-145.jar

After downloading all the .jar files, put all the .jar files in your classpath. I have written a java program by using all these APIs to achieve all the above mentioned functionalities.

Have a look at the following code structure.

  Code for ZipUtil.java
package com.ddlabs.core.zip;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.RandomAccessFile;
import java.util.Arrays;
import java.util.zip.ZipEntry;
import java.util.zip.ZipInputStream;
import java.util.zip.ZipOutputStream;

import net.sf.sevenzipjbinding.ExtractOperationResult;
import net.sf.sevenzipjbinding.ISequentialOutStream;
import net.sf.sevenzipjbinding.ISevenZipInArchive;
import net.sf.sevenzipjbinding.SevenZip;
import net.sf.sevenzipjbinding.SevenZipException;
import net.sf.sevenzipjbinding.impl.RandomAccessFileInStream;
import net.sf.sevenzipjbinding.simple.ISimpleInArchive;
import net.sf.sevenzipjbinding.simple.ISimpleInArchiveItem;

import de.idyl.crypto.zip.AesZipFileEncrypter;

/**
* This is a utility class having utility method for various kinds of
* zip and unzip operation.
* This class performs the following operations.
* 1. Normal zipping a directory
* 2. Zipping a directory with password
* 3. Normal unzipping a zip file
* 4. Unzipping a password protected zip file
*
* @author Debadatta Mishra(PIKU)
*
*/
public final class ZipUtil
{
/**This method is used to write the contents from a zip file to a file
* @param file of type {@link File}
* @param zipIn of type {@link ZipInputStream}
*/
private static void writeFile( File file , ZipInputStream zipIn)
{
try
{
OutputStream outStream = new FileOutputStream(file);
byte[] buff = new byte[1024];
int len;
while ((len = zipIn.read(buff)) > 0)
{
outStream.write(buff, 0, len);
}
outStream.close();
}
catch (Exception e)
{
e.printStackTrace();
}
}

/**This method is used to extract the zip file to a destination directory
* @param srcZipfile of type {@link File} indicating the source zip file
* @param destinationDir of type {@link File} indicating the destination
* directory where the zip file will be extracted.
* @throws IOException
*/
private static void extract(File srcZipfile, File destinationDir) throws IOException
{
ZipInputStream zipIn = null;
try
{
zipIn = new ZipInputStream(new FileInputStream(srcZipfile));
ZipEntry entry = null;

while ((entry = zipIn.getNextEntry()) != null)
{
String outFilename = entry.getName();

if( !new File(destinationDir, outFilename).getParentFile().exists() )
new File(destinationDir, outFilename).getParentFile().mkdirs();

if( !entry.isDirectory() )
writeFile(new File(destinationDir,outFilename), zipIn);
}
System.out.println("Zip file extracted successfully...");
}
catch( Exception e )
{
e.printStackTrace();
}
finally
{
if (zipIn != null)
{
zipIn.close();
}
}
}

/**This method is used to zip or compress a directory to create a zip file.
* @param directory of type String indicating the source directory to be zipped
* @param zos of type {@link ZipOutputStream}
* @param path of type String indicating the path
* @throws IOException
*/
private static void compressDir(String directory, ZipOutputStream zos, String path) throws IOException {
File zipDir = new File(directory);
String[] dirList = zipDir.list();
byte[] readBuffer = new byte[2156];
int bytesIn = 0;
for (int i = 0; i 0)
{
String path = destinationDir+File.separator+item.getPath().substring(0,item.getPath().lastIndexOf(File.separator));

File folderExisting = new File(path);
if (!folderExisting.exists())
new File(path).mkdirs();
}
OutputStream out = new FileOutputStream(destinationDir+File.separator+item.getPath());
out.write(data);
out.close();
}
catch( Exception e )
{
e.printStackTrace();
}
hash[0] |= Arrays.hashCode(data);
return data.length; // Return amount of proceed data
}
},password); /// password.
if (result == ExtractOperationResult.OK)
{
System.out.println(String.format("%9X | %s",
hash[0], item.getPath()));
}
else
{
System.err.println("Error extracting item: " + result);
}
}
}
}
catch (Exception e)
{
e.printStackTrace();
}
finally
{
if (inArchive != null)
{
try
{
inArchive.close();
}
catch (SevenZipException e)
{
System.err.println("Error closing archive: " + e);
e.printStackTrace();
}
}
if (randomAccessFile != null)
{
try
{
randomAccessFile.close();
}
catch (IOException e)
{
System.err.println("Error closing file: " + e);
e.printStackTrace();
}
}
}
}

}

In the above java code, you can achieve the following functionalities.
1.Zip a directory without password like normal zip
2.Zip a directory with password
3.Unzip a zip file to a destination directory
4.Unzip a password protected zip file to a destination directory

Let us look at the Code for the test harness class to test the above functionalities.

Code for TestZipUtil.java
package com.ddlabs.core.zip.test;

import com.ddlabs.core.zip.ZipUtil;

/**This is a test harness class to test all the functionalities defined
* in the ZipUtil class.
* @author Debadatta Mishra(PIKU)
*
*/
public class TestZipUtil
{
public static void main(String[] args)
{
//Normal Zip
//ZipUtil.zipDir("testdata/SWT", "testdata/temp.zip");
//ZipUtil.zipDir("testdata/SWT", null);

//Zip with Password
ZipUtil.zipDirWithPassword("testdata/SWT", "testdata/temp.zip","abcd1234");
//ZipUtil.zipDirWithPassword("testdata/SWT", null,"abcd1234");

//Normal Unzip
//ZipUtil.unzipDir("testdata/temp.zip", "tempdata");
ZipUtil.unzipDirWithPassword("testdata/temp.zip", "tempdata", "abcd1234");

}

}

In the above test harness class, uncomment the lines as per your desire and test it.

Assumptions
I assume that reader of this article has
Knowledge on Java language
Knowledge on running programs in Eclipse editor

Test Case details
I have tested the above program in the following conditions.
OS Name : Windows Vista
Java : 1.6.0_16
Java Editor : Eclipse 3.5
Zip Utility Tool : Winzip version : 14.0

Conclusion
I hope that you will enjoy my article. This article does not bear any commercial significance , it is only meant for learning and for novice developers. In case of any problem or errors , feel free to contact me in the email debadatta.mishra@gmail.com .

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5 Comments

  1. Saira said,

    December 18, 2010 at 8:18 pm

    Hi Mishra,

    I am new to programming but have some general idea of making programs.
    I am confused with few things. Can you please help me out:

    1. if i have the jar file, where would i have to import it. I know how to do it in Eclipse, but how about doing it in a normal run time environment.

    2. For the above program to work, the imports>
    net.sf.xxxx
    de.idyl.xxx
    both of these belong to same package? how can i import it.

    And also at your mentioned url, i don’t find any jar file. It is a zip directly with too many source files but i could not find any jar there.

    I would appreciate if you could give me a step by step approcah for making this thing to work.

    — Saira.

  2. Neville said,

    February 17, 2011 at 7:17 am

    Hi,
    Thanks for this interesting article. I was just looking at your article: ZIP and UNZIP with password in JAVA but I needed information on extracting password protected zip files. Although in your test harness class you have a call to ZipUtil.unzipDirWithPassword(“testdata/temp.zip”, “tempdata”, “abcd1234”); however in the ZipUtil class pasted early in the article the method unzipDirWithPassword is not listed. Is this on purpose and how can I obtain reference to it.

    Thanks a lot
    Neville

  3. Felix said,

    October 20, 2012 at 11:36 pm

    Very shortly this site will be famous among all blog viewers, due
    to it’s good articles

  4. August 24, 2013 at 11:18 am

    Hello! Do you use Twitter? I’d like to follow you if that would be okay. I’m definitely enjoying your blog and look forward to
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  5. Tayyeb said,

    December 15, 2016 at 12:03 pm

    Thanks for the code.
    I’ve one problem,
    I am using struts1.x, and have the uploaded file in FormFile. This will give me just file name(not full path on system) or as file as InputStream.

    The unzipDirWithPassword(…) method works very good, if i pass full path of the file.
    But in FormFile, i do not have such facility.

    1 .So can please suggest me any work around?
    2. How find whether given password to unzip the file is correct or not?

    Thanks again.


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