bouncycastle(6)Learn from others DH
bouncycastle(6)Learn from others DH
DH (Diffie-Hellman)
A will generate the key pair A-key, and share the public key to B.
B will generate the key pair B-key, and share the public key to A.
A will use A-private-key and B-public-key to encrypt the data.
B will use A-public-key and B-private-key to decrypt the data.
B--->A will be opposite.
package com.sillycat.easycastle.encryption;
import java.security.Key;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;
import javax.crypto.Cipher;
import javax.crypto.KeyAgreement;
import javax.crypto.SecretKey;
import javax.crypto.interfaces.DHPrivateKey;
import javax.crypto.interfaces.DHPublicKey;
import javax.crypto.spec.DHParameterSpec;
public abstract class DHCoder extends Coder {
public static final String ALGORITHM = "DH";
/**
* default key size
* <pre>
* DH
* Default Keysize 1024
* Keysize must be a multiple of 64, ranging from 512 to 1024 (inclusive).
* </pre>
*/
private static final int KEY_SIZE = 1024;
/**
* DH need a symmetry like DES to encrypt the data
*/
public static final String SECRET_ALGORITHM = "DES";
private static final String PUBLIC_KEY = "DHPublicKey";
private static final String PRIVATE_KEY = "DHPrivateKey";
/**
* initiate A key pair
* @return
* @throws Exception
*/
public static Map<String, Object> initKey() throws Exception {
KeyPairGenerator keyPairGenerator = KeyPairGenerator
.getInstance(ALGORITHM);
keyPairGenerator.initialize(KEY_SIZE);
KeyPair keyPair = keyPairGenerator.generateKeyPair();
//a public key
DHPublicKey publicKey = (DHPublicKey) keyPair.getPublic();
//a private key
DHPrivateKey privateKey = (DHPrivateKey) keyPair.getPrivate();
Map<String, Object> keyMap = new HashMap<String, Object>(2);
keyMap.put(PUBLIC_KEY, publicKey);
keyMap.put(PRIVATE_KEY, privateKey);
return keyMap;
}
/**
* initiate the b key pair
* @param key
* a public key
* @return
* @throws Exception
*/
public static Map<String, Object> initKey(String aPublicKey) throws Exception {
//convert a public key
byte[] keyBytes = decryptBASE64(aPublicKey);
X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM);
PublicKey pubKey = keyFactory.generatePublic(x509KeySpec);
// generate b private key from a public key
DHParameterSpec dhParamSpec = ((DHPublicKey) pubKey).getParams();
KeyPairGenerator keyPairGenerator = KeyPairGenerator
.getInstance(keyFactory.getAlgorithm());
keyPairGenerator.initialize(dhParamSpec);
KeyPair keyPair = keyPairGenerator.generateKeyPair();
//b public key
DHPublicKey publicKey = (DHPublicKey) keyPair.getPublic();
//b private key
DHPrivateKey privateKey = (DHPrivateKey) keyPair.getPrivate();
Map<String, Object> keyMap = new HashMap<String, Object>(2);
keyMap.put(PUBLIC_KEY, publicKey);
keyMap.put(PRIVATE_KEY, privateKey);
return keyMap;
}
/**
* encryption
*
* @param data
* @param publicKey
* @param privateKey
* @return
* @throws Exception
*/
public static byte[] encrypt(byte[] data, String publicKey,
String privateKey) throws Exception {
//generate the local key from public and private keys.
SecretKey secretKey = getSecretKey(publicKey, privateKey);
//encrypt the data
Cipher cipher = Cipher.getInstance(secretKey.getAlgorithm());
cipher.init(Cipher.ENCRYPT_MODE, secretKey);
return cipher.doFinal(data);
}
/**
* decryption
* @param data
* @param publicKey
* @param privateKey
* @return
* @throws Exception
*/
public static byte[] decrypt(byte[] data, String publicKey,
String privateKey) throws Exception {
// generate the local key from public and private keys
SecretKey secretKey = getSecretKey(publicKey, privateKey);
// decrypt the data
Cipher cipher = Cipher.getInstance(secretKey.getAlgorithm());
cipher.init(Cipher.DECRYPT_MODE, secretKey);
return cipher.doFinal(data);
}
/**
* generate the local key
*
* @param publicKey
* @param privateKey
* @return
* @throws Exception
*/
private static SecretKey getSecretKey(String publicKey, String privateKey)
throws Exception {
//decrypt the public key string
byte[] pubKeyBytes = decryptBASE64(publicKey);
KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM);
X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(pubKeyBytes);
PublicKey pubKey = keyFactory.generatePublic(x509KeySpec);
//decrypt the private key string
byte[] priKeyBytes = decryptBASE64(privateKey);
PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(priKeyBytes);
Key priKey = keyFactory.generatePrivate(pkcs8KeySpec);
KeyAgreement keyAgree = KeyAgreement.getInstance(keyFactory
.getAlgorithm());
keyAgree.init(priKey);
keyAgree.doPhase(pubKey, true);
//generate the local key
SecretKey secretKey = keyAgree.generateSecret(SECRET_ALGORITHM);
return secretKey;
}
/**
* get the private key from key map
* @param keyMap
* @return
* @throws Exception
*/
public static String getPrivateKey(Map<String, Object> keyMap)
throws Exception {
Key key = (Key) keyMap.get(PRIVATE_KEY);
return encryptBASE64(key.getEncoded());
}
/**
* get the public key from key map
* @param keyMap
* @return
* @throws Exception
*/
public static String getPublicKey(Map<String, Object> keyMap)
throws Exception {
Key key = (Key) keyMap.get(PUBLIC_KEY);
return encryptBASE64(key.getEncoded());
}
}
The test case will be as follow:
package com.sillycat.easycastle.encryption;
import static org.junit.Assert.assertEquals;
import java.util.Map;
import org.junit.Test;
public class DHCoderTest {
@Test
public void test() throws Exception {
//generate the public key pair
Map<String, Object> aKeyMap = DHCoder.initKey();
String aPublicKey = DHCoder.getPublicKey(aKeyMap);
String aPrivateKey = DHCoder.getPrivateKey(aKeyMap);
System.out.println("A Public Key:\r" + aPublicKey);
System.out.println("A Private Key:\r" + aPrivateKey);
// B will generate the key pair based on A public key
Map<String, Object> bKeyMap = DHCoder.initKey(aPublicKey);
String bPublicKey = DHCoder.getPublicKey(bKeyMap);
String bPrivateKey = DHCoder.getPrivateKey(bKeyMap);
System.out.println("B Public Key:\r" + bPublicKey);
System.out.println("B Private Key:\r" + bPrivateKey);
System.out.println(" ===============first process================== ");
String aInput = "original data content";
System.out.println("data: " + aInput);
// based on a public key, b private key, encryption
byte[] aCode = DHCoder.encrypt(aInput.getBytes(), aPublicKey,
bPrivateKey);
// based on b public key, a private key, decryption
byte[] aDecode = DHCoder.decrypt(aCode, bPublicKey, aPrivateKey);
String aOutput = (new String(aDecode));
System.out.println("decryption 1: " + aOutput);
assertEquals(aInput, aOutput);
System.out.println(" ===============sencond process================== ");
String bInput = "sencond data content";
System.out.println("data: " + bInput);
byte[] bCode = DHCoder.encrypt(bInput.getBytes(), bPublicKey,
aPrivateKey);
byte[] bDecode = DHCoder.decrypt(bCode, aPublicKey, bPrivateKey);
String bOutput = (new String(bDecode));
System.out.println("decryption 2: " + bOutput);
assertEquals(bInput, bOutput);
}
}
DH is suitable for my system.
references:
http://snowolf.iteye.com/blog/382422
