JAVA加密算法（RSA）

RSA
    这种算法1978年就出现了，它是第一个既能用于数据加密也能用于数字签名的算法。它易于理解和操作，也很流行。算法的名字以发明者的名字命名：Ron Rivest, AdiShamir 和Leonard Adleman。
    这种加密算法的特点主要是密钥的变化，上文我们看到DES只有一个密钥。相当于只有一把钥匙，如果这把钥匙丢了，数据也就不安全了。RSA同时有两把钥匙，公钥与私钥。
    公钥公开，私钥保密。我们用公钥加密数据，用私钥解密数据。能不能反过来呢，用私钥加密，用公钥解密呢？不可以！

通过java代码实现如下：Coder类见 java加密技术（一）
Java代码
import java.security.Key;  
import java.security.KeyFactory;  
import java.security.KeyPair;  
import java.security.KeyPairGenerator;  
import java.security.interfaces.RSAPrivateKey;  
import java.security.interfaces.RSAPublicKey;  
import java.security.spec.PKCS8EncodedKeySpec;  
import java.security.spec.X509EncodedKeySpec;  
 
import java.util.HashMap;  
import java.util.Map;  
 
import javax.crypto.Cipher;  
 
/** 
* RSA安全编码组件 
*  
*/ 
public abstract class RSACoder extends Coder {  
    public static final String ALGORITHM = "RSA";  
    private static final String PUBLIC_KEY = "RSAPublicKey";  
    private static final String PRIVATE_KEY = "RSAPrivateKey";  
 
    /** 
     * 解密<br> 
     * 用私钥解密 
     *  
     * @param data 
     * @param key 
     * @return 
     * @throws Exception 
     */ 
    public static byte[] decrypt(byte[] data, String key) throws Exception {  
        // 对密钥解密  
        byte[] keyBytes = decryptBASE64(key);  
 
        // 取得私钥  
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);  
        KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM);  
        Key privateKey = keyFactory.generatePrivate(pkcs8KeySpec);  
 
        // 对数据解密  
        Cipher cipher = Cipher.getInstance(ALGORITHM);  
        cipher.init(Cipher.DECRYPT_MODE, privateKey);  
 
        return cipher.doFinal(data);  
    }  
 
    /** 
     * 加密<br> 
     * 用公钥加密 
     *  
     * @param data 
     * @param key 
     * @return 
     * @throws Exception 
     */ 
    public static byte[] encrypt(byte[] data, String key) throws Exception {  
        // 对公钥解密  
        byte[] keyBytes = decryptBASE64(key);  
 
        // 取得公钥  
        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);  
        KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM);  
        Key publicKey = keyFactory.generatePublic(x509KeySpec);  
 
        // 对数据加密  
        Cipher cipher = Cipher.getInstance(ALGORITHM);  
        cipher.init(Cipher.ENCRYPT_MODE, publicKey);  
 
        return cipher.doFinal(data);  
    }  
 
    /** 
     * 取得私钥 
     *  
     * @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());  
    }  
 
    /** 
     * 取得公钥 
     *  
     * @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());  
    }  
 
    /** 
     * 初始化密钥 
     *  
     * @return 
     * @throws Exception 
     */ 
    public static Map<String, Object> initKey() throws Exception {  
        KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance(ALGORITHM);  
        keyPairGen.initialize(1024);  
 
        KeyPair keyPair = keyPairGen.generateKeyPair();  
 
        // 公钥  
        RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();  
 
        // 私钥  
        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;  
    }  
} 

import java.security.Key;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;

import java.util.HashMap;
import java.util.Map;

import javax.crypto.Cipher;

/**
* RSA安全编码组件
*
*/
public abstract class RSACoder extends Coder {
public static final String ALGORITHM = "RSA";
private static final String PUBLIC_KEY = "RSAPublicKey";
private static final String PRIVATE_KEY = "RSAPrivateKey";

/**
* 解密<br>
* 用私钥解密
*
* @param data
* @param key
* @return
* @throws Exception
*/
public static byte[] decrypt(byte[] data, String key) throws Exception {
// 对密钥解密
byte[] keyBytes = decryptBASE64(key);

// 取得私钥
PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM);
Key privateKey = keyFactory.generatePrivate(pkcs8KeySpec);

// 对数据解密
Cipher cipher = Cipher.getInstance(ALGORITHM);
cipher.init(Cipher.DECRYPT_MODE, privateKey);

return cipher.doFinal(data);
}

/**
* 加密<br>
* 用公钥加密
*
* @param data
* @param key
* @return
* @throws Exception
*/
public static byte[] encrypt(byte[] data, String key) throws Exception {
// 对公钥解密
byte[] keyBytes = decryptBASE64(key);

// 取得公钥
X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM);
Key publicKey = keyFactory.generatePublic(x509KeySpec);

// 对数据加密
Cipher cipher = Cipher.getInstance(ALGORITHM);
cipher.init(Cipher.ENCRYPT_MODE, publicKey);

return cipher.doFinal(data);
}

/**
* 取得私钥
*
* @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());
}

/**
* 取得公钥
*
* @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());
}

/**
* 初始化密钥
*
* @return
* @throws Exception
*/
public static Map<String, Object> initKey() throws Exception {
KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance(ALGORITHM);
keyPairGen.initialize(1024);

KeyPair keyPair = keyPairGen.generateKeyPair();

// 公钥
RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();

// 私钥
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;
}
}

再给出一个测试类：
Java代码
import static org.junit.Assert.*;  
 
import org.junit.Test;  
 
import java.util.Map;  
 
/** 
*  
*/ 
public class RSACoderTest {  
 
    @Test 
    public void test() throws Exception {  
        String inputStr = "abc";  
        byte[] data = inputStr.getBytes();  
 
        Map<String, Object> keyMap = RSACoder.initKey();  
 
        String publicKey = RSACoder.getPublicKey(keyMap);  
        String privateKey = RSACoder.getPrivateKey(keyMap);  
        System.err.println("公钥: \n\r" + publicKey);  
        System.err.println("私钥： \n\r" + privateKey);  
 
        byte[] encodedData = RSACoder.encrypt(data, publicKey);  
 
        byte[] decodedData = RSACoder.decrypt(encodedData, privateKey);  
        String outputStr = new String(decodedData);  
        System.err.println("加密前: " + inputStr + "\n\r" + "解密后: " + outputStr);  
        assertEquals(inputStr, outputStr);  
    }  
 
} 

import static org.junit.Assert.*;

import org.junit.Test;

import java.util.Map;

/**
*
*/
public class RSACoderTest {

@Test
public void test() throws Exception {
String inputStr = "abc";
byte[] data = inputStr.getBytes();

Map<String, Object> keyMap = RSACoder.initKey();

String publicKey = RSACoder.getPublicKey(keyMap);
String privateKey = RSACoder.getPrivateKey(keyMap);
System.err.println("公钥: \n\r" + publicKey);
System.err.println("私钥： \n\r" + privateKey);

byte[] encodedData = RSACoder.encrypt(data, publicKey);

byte[] decodedData = RSACoder.decrypt(encodedData, privateKey);
String outputStr = new String(decodedData);
System.err.println("加密前: " + inputStr + "\n\r" + "解密后: " + outputStr);
assertEquals(inputStr, outputStr);
}

}

控制台输出：
Console代码
公钥:   
 
MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCAiF0wxZP16aO4ZjUAj1bxFzhx157bB/hBpKyi  
lh68cg5cTm5QQvWcc1duLdXyR4EH0O557qONMKopsTNIGGrpDRWVU1RIlpCOk+53MmEVm/R/Gmj7  
l0ccckrDl4Dx1hWEtxqgXh6H/DDk6Ldns4RYVj0evqj7l1KESNvNWjQlBwIDAQAB  
 
私钥：   
 
MIICdwIBADANBgkqhkiG9w0BAQEFAASCAmEwggJdAgEAAoGBAICIXTDFk/Xpo7hmNQCPVvEXOHHX  
ntsH+EGkrKKWHrxyDlxOblBC9ZxzV24t1fJHgQfQ7nnuo40wqimxM0gYaukNFZVTVEiWkI6T7ncy  
YRWb9H8aaPuXRxxySsOXgPHWFYS3GqBeHof8MOTot2ezhFhWPR6+qPuXUoRI281aNCUHAgMBAAEC  
gYBGJiZ2T98I/5LTOTUEMTcKLdooh72zXQ4pBW8S7UupHbaoukWKmIDj+i9leq6hpFTPp0AAXDX3  
APBeANA0MN9nvCY9Bxs7IwKlfsi2/IiQbacCwEvvnl7MDVD3BoOBLijLXylr2vWez2M1/+DcEfLf  
hFCx85j/8KWxha3RKrQMwQJBALmeFACUwGD9LgNXXB9GAPCbec/hKBkgPWQP+MDQsATWukAXGRMT  
JKET2AUiWqQjE1aNS87H6PapGR+M6Cf38zsCQQCxRQ1zyLwKTfoexj61b2LWz3v93yUgQp/BlSvk  
/CBAmQSyTHQUlOisdmQvZluKYKETRHpUDzKCKQfoyITxJyClAkEAgcPy5ekYiXXWyj0zySVOmOeJ  
BHy7ZL12TdMgq+P5epiHwzCitgQnEnlmB0jaJ2/iIBtOCTUXOAJF7xm6X97nawJBAKZFjbOfgfjs  
YQHCkwkdXAj+fl+GkU0sEKrDn3NdpWbR4BzZJzwy2/b/6UKocI5fylXHMjJsOsTpdXi7tC55s90C  
QEyv+TwMomqkUU/X/I3JfWnh027RS3cOH1jEQA+xL5oPYnD1zI8FYdV2q0knFwMMVpJQDD+KbAdC  
1uWAAj3fbls=  
 
加密前: abc  
 
解密后: abc 

公钥:

MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCAiF0wxZP16aO4ZjUAj1bxFzhx157bB/hBpKyi
lh68cg5cTm5QQvWcc1duLdXyR4EH0O557qONMKopsTNIGGrpDRWVU1RIlpCOk+53MmEVm/R/Gmj7
l0ccckrDl4Dx1hWEtxqgXh6H/DDk6Ldns4RYVj0evqj7l1KESNvNWjQlBwIDAQAB

私钥：
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加密前: abc

解密后: abc


如果公钥只能加密，私钥只能解密，但是双方都需要互通加密数据该怎么办？使用DH加密算法！