Exploring XML Encryption, Part 1

Demonstrating the secure exchange of structured data

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Listing 11. XmlEncryption.java
	Listing 11
	A wrapper class that can generate complete XML encrypted file.
	It uses all the other classes. 
	Users of our XML Encryption Engine will only need to interact with 
	this class.

import java.io.*;
import org.w3c.dom.*;
import javax.xml.parsers.*;
import org.apache.crimson.tree.XmlDocument;

public class XmlEncryption {
	// Source and Result file names.
	private String fileSource = null;
	private String fileResult = null;
	// Name of Algorithm which will be used to encrypt data.
	private String algoName = null;

	// Name of Secret key which was previously agreed upon 
	// and saved with the given name.
	private String keyName = null; 
	// Id attribute of Main structure 
	private String encId = null;

	// It will be used to get New Document Objects.
	private DocumentBuilder docBuilder = null;

	// Default Constructor
	public XmlEncryption() {
		// Create DocumentBuilder object from DocumentBuilderFactory.
		try {
			docBuilder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
		} catch (ParserConfigurationException e){ docBuilder = null; }
	// Get the new Document object for DocumentBuilder
	private Document getNewDocument() {
		if (docBuilder != null)
			return docBuilder.newDocument();
			return null;	
	// Generate Complete XML Encrypted File.
	public void encryptCompleteXmlFile(){
		// Take an Object of EncryptedData Class. 
		// It represents EncryptedData Element.
		EncryptedData encDataObj = this.getEncryptedDataDoc(this.encId, "DOCUMENT");

		// Get XML Structure for EncryptionMehtod element.
		Document encMethodDoc = this.getEncryptionMethodDoc(this.algoName);	

		// Get XML Structure for KeyInfo element.		
		Document encKeyInfoDoc = this.getKeyInfoDoc(this.keyName);

		// Read the given file data which will be encrypted.
		String plainData = this.readFile(fileSource);

		// Use of JCA/JCE to get encrypted data.
		String cipherData = this.getEncryptedData(plainData);

		// Get XML Structure for CipherData element.				
		Document cipherDataDoc = this.getCipherDataDoc(cipherData);

		// Join these XML Structures.
		// Now Save this Document as an XML File
		this.saveEncryptedFile(this.fileResult, encDataObj.getEncData());		
	}// End encryptCompleteXmlFile()
	//********** All Set/Get methods to related fields.
	public void setFileSource(String file) {
		this.fileSource = file;
	}// End setFileSource()
	public String getFileSource() {
		return this.fileSource;
	}// End getFileSource()

	public void setFileResult(String file) {
		this.fileResult = file;
	}// End setFileResult() 
	public String getFileResult() {
		return this.fileResult;
	}// End getFileResult() 
	public void setAlgoName(String name) {
		this.algoName = name;
	}// End setAlgoName() 

	public String getAlgoName() {
		return this.algoName;
	}// End getAlgoName() 
	public void setKeyName (String key) {
		this.keyName = key; 
	}// End setKeyName()
	public String getKeyName() {
		return this.keyName; 
	}// End getKeyName()

	public void setEncId (String id) {
		this.encId = id;
	}// End setEncId()

	public String getEncId() {
		return this.encId;
	}// End setEncId()


	// Reads the given file and returns it as string.		
	public String readFile(String fileName){
		String xml = "";
		try {
			FileInputStream in = new FileInputStream(fileName);
			byte [] data = new byte[in.available()];
			xml = new String(data);
		} catch (IOException e) { }
		return xml;
	}// End readFile()
	// Saves the given document as an XML (Text) file with given name.
	public void saveEncryptedFile (String fileName, Document doc) {
		XmlDocument xmlDoc = (XmlDocument)doc;
		try { 
			OutputStream out = new FileOutputStream(fileName);
		} catch (IOException e) { }

	}// End saveEncryptedFile()
	// Returns the EncryptedData Object.
	public EncryptedData getEncryptedDataDoc(String Id, String encType) {
		EncryptedData ed = new EncryptedData(this.getNewDocument());
		if (encType.equals("DOCUMENT"))
		return ed;
	}// End getEncryptedDataDoc()

	// Returns the EncryptionMehtod Structure.
	public Document getEncryptionMethodDoc (String algoName) {
		EncryptionMethod em = new EncryptionMethod(this.getNewDocument());
		if (algoName.equals("TripleDes-cbc"))
		return em.getEncMethod();
	}// End getEncryptionMethodDoc()

	// Returns the KeyInfo Structure.
	public Document getKeyInfoDoc (String keyName) {
		GenericKeyInfo ki = new GenericKeyInfo(this.getNewDocument(),"ds", AlgoNames.XML_DSIG);
		return ki.getKeyInfo();	
	}// End getKeyInfoDoc()
	// Returns the CipherData Structure.
	public Document getCipherDataDoc (String data) {
		CipherData cd = new CipherData(this.getNewDocument());
		return cd.getCipherData();
	}// getCipherDataDoc()
	// In the future, all JCA/JCE related classes will be used here.
	// It will take plain text and return its encrypted form. 
	// All necessary Infromation about keys and algos will be 
	// taken from the fields representing them. 
	// For the time being it is not doing any thing.
	public String getEncryptedData(String data) {
		return "This is Cipher Data";
	}// End getEncryptedData()
	// This main method is only included to demonstrate functionality.
	public static void main (String args[]) {
		XmlEncryption xmlEnc = new XmlEncryption();
	}// End main()
}// End Class DemoApplication

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