bouncycastle(5)Learn from others RSA
bouncycastle(5)Learn from others RSA
RSA
There are 2 keys in RSA, one is private, one is public. They can be used to encrypt/decrypt and signing.
A will generate private/public key pair. A shares the public key to B.
A will sign and encrypt the data, send the data to B.
B will use public key to validate the signing and decrypt the data.
B will use public key to encrypt the data.
A will use private key to decrypt the data.
The implementation class is as follow:
package com.sillycat.easycastle.encryption;
import javax.crypto.Cipher;
public class RSACoder extends Coder {
public static final String KEY_ALGORITHM = "RSA";
public static final String SIGNATURE_ALGORITHM = "MD5withRSA";
private static final String PUBLIC_KEY = "RSAPublicKey";
private static final String PRIVATE_KEY = "RSAPrivateKey";
/**
* use private key to generate the signing data
* @param data
* @param privateKey
* @return
* @throws Exception
*/
public static String sign(byte[] data, String privateKey) throws Exception {
// decrypt the private key via base64
byte[] keyBytes = decryptBASE64(privateKey);
// construct PKCS8EncodedKeySpec object
PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
// KEY_ALGORITHM RSA
KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
// convert to key object from private key string
PrivateKey priKey = keyFactory.generatePrivate(pkcs8KeySpec);
// signature
Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
signature.initSign(priKey);
signature.update(data);
return encryptBASE64(signature.sign());
}
/**
* validate the signature
* @param data
* @param publicKey
* @param sign
*
* @return true false
* @throws Exception
*/
public static boolean verify(byte[] data, String publicKey, String sign)
throws Exception {
// decrypt the public key via base64
byte[] keyBytes = decryptBASE64(publicKey);
// construct X509EncodedKeySpec object
X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);
// KEY_ALGORITHM
KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
// convert to public key from public key string
PublicKey pubKey = keyFactory.generatePublic(keySpec);
Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
signature.initVerify(pubKey);
signature.update(data);
// validate the signature
return signature.verify(decryptBASE64(sign));
}
/**
* decryption via private key
*
* @param data
* @param key
* @return
* @throws Exception
*/
public static byte[] decryptByPrivateKey(byte[] data, String privateKeyString)
throws Exception {
// decrypt key from string
byte[] keyBytes = decryptBASE64(privateKeyString);
// get the private key
PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
Key privateKey = keyFactory.generatePrivate(pkcs8KeySpec);
// decrypt the data via private key
Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
cipher.init(Cipher.DECRYPT_MODE, privateKey);
return cipher.doFinal(data);
}
/**
* decrypt via public key
*
* @param data
* @param key
* @return
* @throws Exception
*/
public static byte[] decryptByPublicKey(byte[] data, String publicKeyString)
throws Exception {
// decrypt the key string
byte[] keyBytes = decryptBASE64(publicKeyString);
// convert the key object to get the public key
X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
Key publicKey = keyFactory.generatePublic(x509KeySpec);
// decrypt the data with public key
Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
cipher.init(Cipher.DECRYPT_MODE, publicKey);
return cipher.doFinal(data);
}
/**
* encrypt via public key
*
* @param data
* @param key
* @return
* @throws Exception
*/
public static byte[] encryptByPublicKey(byte[] data, String publicKeyString)
throws Exception {
// decrypt the public key
byte[] keyBytes = decryptBASE64(publicKeyString);
// convert to public key object
X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
Key publicKey = keyFactory.generatePublic(x509KeySpec);
// encrypt the data via public key
Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
cipher.init(Cipher.ENCRYPT_MODE, publicKey);
return cipher.doFinal(data);
}
/**
* encrypt the data via private key
*
* @param data
* @param key
* @return
* @throws Exception
*/
public static byte[] encryptByPrivateKey(byte[] data, String privateKeyString)
throws Exception {
// decrypt the key from string
byte[] keyBytes = decryptBASE64(privateKeyString);
// convert to private key object
PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
Key privateKey = keyFactory.generatePrivate(pkcs8KeySpec);
// encrypt the data
Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
cipher.init(Cipher.ENCRYPT_MODE, privateKey);
return cipher.doFinal(data);
}
/**
* get the private key
*
* @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 public key
*
* @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());
}
/**
* initiate the key pair
* @return
* @throws Exception
*/
public static Map<String, Object> initKey() throws Exception {
KeyPairGenerator keyPairGen = KeyPairGenerator
.getInstance(KEY_ALGORITHM);
keyPairGen.initialize(1024);
KeyPair keyPair = keyPairGen.generateKeyPair();
// public key
RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
// private key
RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();
Map<String, Object> keyMap = new HashMap<String, Object>(2);
keyMap.put(PUBLIC_KEY, publicKey);
keyMap.put(PRIVATE_KEY, privateKey);
return keyMap;
}
}
And the test class is as follow:
package com.sillycat.easycastle.encryption;
import static org.junit.Assert.*;
import java.util.Map;
import org.junit.Before;
import org.junit.Test;
public class RSACoderTest {
private String publicKey;
private String privateKey;
@Before
public void setUp() throws Exception {
Map<String, Object> keyMap = RSACoder.initKey();
publicKey = RSACoder.getPublicKey(keyMap);
privateKey = RSACoder.getPrivateKey(keyMap);
System.out.println("public key : \n\r" + publicKey);
System.out.println("private key: \n\r" + privateKey);
}
@Test
public void test() throws Exception {
System.out.println("public key encryption——private key decryption");
String inputStr = "hello, sillycat.";
byte[] data = inputStr.getBytes();
byte[] encodedData = RSACoder.encryptByPublicKey(data, publicKey);
byte[] decodedData = RSACoder.decryptByPrivateKey(encodedData,
privateKey);
String outputStr = new String(decodedData);
System.out.println("original: " + inputStr + "\n\r" + "decryption: " + outputStr);
assertEquals(inputStr, outputStr);
}
@Test
public void testSign() throws Exception {
System.out.println("private encryption——public decryption");
String inputStr = "hello, kiko.";
byte[] data = inputStr.getBytes();
byte[] encodedData = RSACoder.encryptByPrivateKey(data, privateKey);
byte[] decodedData = RSACoder
.decryptByPublicKey(encodedData, publicKey);
String outputStr = new String(decodedData);
System.out.println("original: " + inputStr + "\n\r" + "decryption: " + outputStr);
assertEquals(inputStr, outputStr);
System.out.println("private signature——public validate the signature");
// generate signature
String sign = RSACoder.sign(encodedData, privateKey);
System.out.println("singature string :\r" + sign);
// validate signature string
boolean status = RSACoder.verify(encodedData, publicKey, sign);
System.out.println("status:\r" + status);
assertTrue(status);
}
}
references:
http://snowolf.iteye.com/blog/381767
