RSA用私鑰加密。。

RSA是一種使用非對稱加密的算法，以前總認爲只有公鑰加密，私鑰解密的，現在看到了一篇關於私鑰加密，公鑰解密的文章(懷疑人生~),現把代碼貼在下面：(正確的方式是公鑰加密，私鑰解密，私鑰加簽，公鑰驗籤(:-加密是爲了防止信息被泄露，而簽名是爲了防止信息被篡改-: ))

package coms.nas;

import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import javax.crypto.Cipher;
import sun.misc.BASE64Decoder;
import sun.misc.BASE64Encoder;

public class RSAUtil {
	public static String data = "12345";
	public static BASE64Encoder base64Encoder = new BASE64Encoder();
	public static BASE64Decoder base64Decoder = new BASE64Decoder();
	// 公鑰
	private static String publicKeyStr = "MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQC/OpVr+aQu6B3stSUgsLcZWpaxatset8zTqat1FF543hoECcTnRqDXKwfX09J+RLCc/1fbITt0s4wUUwJNU7lKJSTGZp5/xHcEiFJjTa+XY6pQHQKvvZjAQMkyzC3H5tmaNTapKYJOAWw7u1dxcRNFdD3k5E+EiqSnlo30u7SLCwIDAQAB";
	// 私鑰
	private static String privateKeyStr = "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";
	private static RSAUtil ourInstance = new RSAUtil();

	public static RSAUtil getInstance() {
		return ourInstance;
	}

	// 生成密鑰對
	private void generateKeyPair() throws NoSuchAlgorithmException {
		KeyPairGenerator keyPairGenerator;
		keyPairGenerator = KeyPairGenerator.getInstance("RSA");
		keyPairGenerator.initialize(1024);
		KeyPair keyPair = keyPairGenerator.generateKeyPair();
		// 獲取公鑰，並以base64格式打印出來
		PublicKey publicKey = keyPair.getPublic();
		publicKeyStr = new String(base64Encoder.encode(publicKey.getEncoded()));
		// 獲取私鑰，並以base64格式打印出來
		PrivateKey privateKey = keyPair.getPrivate();
		privateKeyStr = new String(base64Encoder.encode(privateKey.getEncoded()));
	}

	// 將base64編碼後的公鑰字符串轉成PublicKey實例
	private static PublicKey getPublicKey(String publicKey) throws Exception {
		byte[] keyBytes = base64Decoder.decodeBuffer(publicKey);
		X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);
		KeyFactory keyFactory = KeyFactory.getInstance("RSA");
		return keyFactory.generatePublic(keySpec);
	}

	// 將base64編碼後的私鑰字符串轉成PrivateKey實例
	private static PrivateKey getPrivateKey(String privateKey) throws Exception {
		byte[] keyBytes = base64Decoder.decodeBuffer(privateKey);
		PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(keyBytes);
		KeyFactory keyFactory = KeyFactory.getInstance("RSA");
		return keyFactory.generatePrivate(keySpec);
	}

	// 公鑰加密
	public static String encryptByPublicKey(String content) throws Exception {
		// 獲取公鑰
		PublicKey publicKey = getPublicKey(publicKeyStr);
		Cipher cipher = Cipher.getInstance("RSA");
		cipher.init(Cipher.ENCRYPT_MODE, publicKey);
		byte[] cipherText = cipher.doFinal(content.getBytes());
		String cipherStr = base64Encoder.encode(cipherText);
		return cipherStr;
	}

	// 私鑰加密
	public static String encryptByPrivateKey(String content) throws Exception {
		// 獲取私鑰
		PrivateKey privateKey = getPrivateKey(privateKeyStr);
		Cipher cipher = Cipher.getInstance("RSA");
		cipher.init(Cipher.ENCRYPT_MODE, privateKey);
		byte[] cipherText = cipher.doFinal(content.getBytes());
		String cipherStr = base64Encoder.encode(cipherText);
		return cipherStr;
	}

	// 私鑰解密
	public static String decryptByPrivateKey(String content) throws Exception {
		// 獲取私鑰
		PrivateKey privateKey = getPrivateKey(privateKeyStr);
		Cipher cipher = Cipher.getInstance("RSA");
		cipher.init(Cipher.DECRYPT_MODE, privateKey);
		byte[] cipherText = base64Decoder.decodeBuffer(content);
		byte[] decryptText = cipher.doFinal(cipherText);
		return new String(decryptText);
	}

	// 公鑰解密
	public static String decryptByPublicKey(String content) throws Exception {
		// 獲取公鑰
		PublicKey publicKey = getPublicKey(publicKeyStr);
		Cipher cipher = Cipher.getInstance("RSA");
		cipher.init(Cipher.DECRYPT_MODE, publicKey);
		byte[] cipherText = base64Decoder.decodeBuffer(content);
		byte[] decryptText = cipher.doFinal(cipherText);
		return new String(decryptText);
	}


	public static void main(String[] args) throws Exception {
		System.out.println("初始數據："+data);
		// 公鑰加密
		String encryptedBytes = encryptByPublicKey(data);
		System.out.println("公鑰加密後：" + encryptedBytes);
		// 私鑰解密
		String decryptedBytes = decryptByPrivateKey(encryptedBytes);
		System.out.println("私鑰解密後：" + decryptedBytes);
		// 私鑰加密
		String encryptedBytes2 = encryptByPrivateKey(data);
		System.out.println("私鑰加密後：" + encryptedBytes2);
		// 公鑰解密
		String decryptedBytes2 = decryptByPublicKey(encryptedBytes2);
		System.out.println("公鑰解密後：" + decryptedBytes2);
	}
}