jCryption for Java
Requirements
JDK 1.4+
Bouncy Castle Crypto APIs
- http://www.bouncycastle.org/latest_releases.html - tested with
bcprov-jdk14-136.jarJava class
Just simple class in java to provide exact functionality as php version of library.
package com.fg.lib.shared.v1.cryptography;
import org.bouncycastle.jce.provider.BouncyCastleProvider;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.GeneralSecurityException;
import java.security.interfaces.RSAPublicKey;
import java.util.Map;
import java.util.HashMap;
import java.net.URLDecoder;
import java.io.UnsupportedEncodingException;
import javax.crypto.Cipher;
/**
* jCryption support (www.jcryption.org) - RSA encryption
* @author Michal Franc, FG Forrest (c) 2009
* 18.10.2009 10:35:24
*/
public class jCryption {
/**
* Constructor
*/
public jCryption() {
java.security.Security.addProvider(new BouncyCastleProvider());
}
/**
* Generates the Keypair with the given keyLength.
*
* @param keyLength length of key
* @return KeyPair object
* @throws RuntimeException if the RSA algorithm not supported
*/
public KeyPair generateKeypair(int keyLength) {
try {
KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA");
kpg.initialize(keyLength);
return kpg.generateKeyPair();
} catch (NoSuchAlgorithmException e) {
throw new RuntimeException("RSA algorithm not supported",e);
}
}
/**
* Decrypts a given string with the RSA keys
* @param encrypted full encrypted text
* @param keys RSA keys
* @return decrypted text
* @throws RuntimeException if the RSA algorithm not supported or decrypt operation failed
*/
public String decrypt( String encrypted, KeyPair keys ) {
Cipher dec;
try {
dec = Cipher.getInstance("RSA/NONE/NoPadding");
dec.init(Cipher.DECRYPT_MODE, keys.getPrivate());
} catch (GeneralSecurityException e) {
throw new RuntimeException("RSA algorithm not supported",e);
}
String[] blocks = encrypted.split("\\s");
StringBuffer result = new StringBuffer();
try {
for ( int i = blocks.length-1; i >= 0; i-- ) {
byte[] data = hexStringToByteArray(blocks[i]);
byte[] decryptedBlock = dec.doFinal(data);
result.append( new String(decryptedBlock) );
}
} catch (GeneralSecurityException e) {
throw new RuntimeException("Decrypt error",e);
}
return result.reverse().toString();
}
/**
* Parse url string (Todo - better parsing algorithm)
* @param url value to parse
* @param encoding encoding value
* @return Map with param name, value pairs
*/
public static Map parse(String url,String encoding) {
try {
String urlToParse = URLDecoder.decode(url,encoding);
String[] params = urlToParse.split("&");
Map parsed = new HashMap();
for (int i = 0; i<params.length; i++ ) {
String[] p = params[i].split("=");
String name = p[0];
String value = (p.length==2)?p[1]:null;
parsed.put(name, value);
}
return parsed;
} catch (UnsupportedEncodingException e) {
throw new RuntimeException("Unknown encoding.",e);
}
}
/**
* Return public RSA key modulus
* @param keyPair RSA keys
* @return modulus value as hex string
*/
public static String getPublicKeyModulus( KeyPair keyPair ) {
RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
return publicKey.getModulus().toString(16);
}
/**
* Return public RSA key exponent
* @param keyPair RSA keys
* @return public exponent value as hex string
*/
public static String getPublicKeyExponent( KeyPair keyPair ) {
RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
return publicKey.getPublicExponent().toString(16);
}
/**
* Max block size with given key length
* @param keyLength length of key
* @return numeber of digits
*/
public static int getMaxDigits(int keyLength) {
return ((keyLength *2)/16)+3;
}
/**
* Convert byte array to hex string
* @param bytes input byte array
* @return Hex string representation
*/
public static String byteArrayToHexString(byte[] bytes) {
StringBuffer result = new StringBuffer();
for (int i=0; i < bytes.length; i++) {
result.append( Integer.toString( ( bytes[i] & 0xff ) + 0x100, 16).substring( 1 ) );
}
return result.toString();
}
/**
* Convert hex string to byte array
* @param data input string data
* @return bytes
*/
public static byte[] hexStringToByteArray(String data) {
int k = 0;
byte[] results = new byte[data.length() / 2];
for (int i = 0; i < data.length();) {
results[k] = (byte) (Character.digit(data.charAt(i++), 16) << 4);
results[k] += (byte) (Character.digit(data.charAt(i++), 16));
k++;
}
return results;
}
}
Example
JSP example (not production code style, in single JSP to be simple)
<%@ page import="com.fg.lib.shared.v1.cryptography.jCryption" %>
<%@ page import="java.security.KeyPair" %>
<%@ page import="java.util.Map" %>
<%@ page contentType="text/html;charset=windows-1250" language="java" %><%
int KEY_SIZE = 1024;
String SESSION_KEY = "jCryptionKeys";
jCryption jc = new jCryption();
// generate keys
if (request.getParameter("generateKeypair")!=null) {
KeyPair keys = jc.generateKeypair(KEY_SIZE);
session.setAttribute(SESSION_KEY,keys);
String e = jCryption.getPublicKeyExponent(keys);
String n = jCryption.getPublicKeyModulus(keys);
String md = String.valueOf(jCryption.getMaxDigits(KEY_SIZE));
out.print("{\"e\":\"");
out.print(e);
out.print("\",\"n\":\"");
out.print(n);
out.print("\",\"maxdigits\":\"");
out.print(md);
out.print("\"}");
}
else {
// process login
%><html>
<head><title>Login form</title></head>
<meta http-equiv="Content-Type" content="text/html; charset=windows-1250">
<script type="text/javascript" src="<%=request.getContextPath()%>/rs/jquery-1.3.2.min.js"></script>
<script type="text/javascript" src="<%=request.getContextPath()%>/rs/jquery.jcryption-1.0.1.min.js" ></script>
<script type="text/javascript">
$(document).ready(function() {
var $statusText = $('<span id="status"></span>').hide();
$("#status_container").append($statusText);
$("#lf").jCryption({
getKeysURL:"<%=request.getContextPath()%>/jc.jsp?generateKeypair=true",
beforeEncryption:function() {$statusText.text("Šifrování - generování RSA klíče.").show();return true;},
encryptionFinished:function(encryptedString, objectLength) {
$statusText.text("Šifrování dokončeno, odesílám.");
return true;
}
});
});
</script>
<body>
<%
KeyPair keys = (KeyPair)request.getSession().getAttribute(SESSION_KEY);
String encrypted = request.getParameter("jCryption");
String username = null;
String password = null;
// decrypt
if ( encrypted!=null && keys!=null ) {
try {
String data = jc.decrypt(encrypted, keys);
request.getSession().removeAttribute(SESSION_KEY);
Map params = jCryption.parse(data,"windows-1250");
username = (String)params.get("user");
password = (String)params.get("password");
} catch ( Throwable e ) {
e.printStackTrace();
}
}
%>
posted user: <%=username%><br>
posted password: <%=password%><hr>
<form id="lf" action="<%=request.getContextPath()%>/jc.jsp" method="post">
<fieldset>
<legend>login</legend>
<div>
<div>username:<br><input type="text" size="45" name="user" value=""></div>
<div>password:<br><input type="password" size="45" name="password" value=""></div>
</div>
<div>
<p><input type="submit"/><span id="status_container"></span></p>
</div>
</fieldset>
</form>
</body>
</html><%
}
%>