Java非對稱加密(公鑰加密，私鑰解密)

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.security.Key;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import javax.crypto.Cipher;

/**

公鑰加密，私鑰解密(非對稱加密)
*/
public class AsymmetricEncryption {
public static void main(String[] args) throws Exception {

 publicEnrypy();
 privateEncode();

}
/**

加密的方法,使用公鑰進行加密
@throws Exception
*/
public static void publicEnrypy() throws Exception {
Cipher cipher = Cipher.getInstance("RSA");
KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
// 生成鑰匙對
 KeyPair keyPair = keyPairGenerator.generateKeyPair();
// 得到公鑰
 Key publicKey = keyPair.getPublic();
// 得到私鑰
 Key privateKey = keyPair.getPrivate();
// 設置為加密模式
 cipher.init(Cipher.ENCRYPT_MODE, publicKey);
// 對數據進行加密
 byte[] result = cipher.doFinal("aaa".getBytes());
//把私鑰保存到硬盤上
 saveKey(privateKey);
//把加密后的數據保存到硬盤上
 saveData(result);
}
/**

解密的方法，使用私鑰進行解密
@throws Exception
*/
public static void privateEncode() throws Exception {
 Cipher cipher = Cipher.getInstance("RSA");
// 從硬盤中讀取私鑰
 Key privateKey = loadKey();
//設置為解密模式，用私鑰解密
 cipher.init(Cipher.DECRYPT_MODE, privateKey);
// 從硬盤中讀取加密后的數據
 byte[] data = loadData();
//對加密后的數據進行解密，返回解密后的結果
 byte[] result = cipher.doFinal(data);
System.out.println(new String(result));
}
/**

從硬盤中加載加密后的文件
@return
@throws FileNotFoundException
@throws IOException
*/
private static byte[] loadData() throws FileNotFoundException, IOException {
 FileInputStream fileInputStream = new FileInputStream(new File(

     "E://data.data"));

ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
 int len = 0;
while ((len = fileInputStream.read(buffer)) != -1) {

 outputStream.write(buffer, 0, len);

}
fileInputStream.close();
return outputStream.toByteArray();
}
/**

從硬盤中加載私鑰
@return
@throws IOException
@throws FileNotFoundException
@throws ClassNotFoundException
*/
private static Key loadKey() throws IOException, FileNotFoundException,

 ClassNotFoundException {

ObjectInputStream inputStream = new ObjectInputStream(

     new FileInputStream(new File("E://private_key")));

Key privateKey = (Key) inputStream.readObject();
 return privateKey;
}
/**

把加密后的密文保存到硬盤上
@param result
@throws FileNotFoundException
@throws IOException
*/
private static void saveData(byte[] result) throws FileNotFoundException,

 IOException {

FileOutputStream fileOutputStream = new FileOutputStream(new File(

     "E://data.data"));

fileOutputStream.write(result);
}
/**

把私鑰保存到硬盤上
@param privateKey
@throws IOException
@throws FileNotFoundException
*/
private static void saveKey(Key privateKey) throws IOException,
 FileNotFoundException {

 ObjectOutputStream outputStream = new ObjectOutputStream(
     new FileOutputStream(new File("E://private_key")));

 outputStream.writeObject(privateKey);
}



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