Android RSA加密解密

時間 2019-12-01

原文原文鏈接

概述php

RSA是目前最有影響力的公鑰加密算法，該算法基於一個十分簡單的數論事實：將兩個大素數相乘十分容易，但那時想要對其乘積進行因式分解卻極其困難，所以能夠將乘積公開做爲加密密鑰，即公鑰，而兩個大素數組合成私鑰。公鑰是可發佈的供任何人使用，私鑰則爲本身全部，供解密之用。關於RSA其它須要瞭解的知識，參考維基百科:http://zh.wikipedia.org/zh-cn/RSA%E5%8A%A0%E5%AF%86%E6%BC%94%E7%AE%97%E6%B3%95前端

在項目開發中對於一些比較敏感的信息須要對其進行加密處理，咱們就可使用RSA這種非對稱加密算法來對數據進行加密處理。java

使用android

祕鑰對的生成ios

一、咱們能夠在代碼裏隨機生成密鑰對算法

    /**
     * 隨機生成RSA密鑰對
     * 
     * @param keyLength
     *            密鑰長度，範圍：512～2048<br>
     *            通常1024
     * @return
     */
    public static KeyPair generateRSAKeyPair(int keyLength)
    {
        try
        {
            KeyPairGenerator kpg = KeyPairGenerator.getInstance(RSA);
            kpg.initialize(keyLength);
            return kpg.genKeyPair();
        } catch (NoSuchAlgorithmException e)
        {
            e.printStackTrace();
            return null;
        }
    }

二、下載開源RSA密鑰生成工具openssl（一般Linux系統都自帶該程序），解壓縮至獨立的文件夾，進入其中的bin目錄，執行如下命令：數組

openssl genrsa -out rsa_private_key.pem 1024
openssl pkcs8 -topk8 -inform PEM -in rsa_private_key.pem -outform PEM -nocrypt -out private_key.pem
openssl rsa -in rsa_private_key.pem -pubout -out rsa_public_key.pem

第一條命令生成原始 RSA私鑰文件 rsa_private_key.pem，第二條命令將原始 RSA私鑰轉換爲 pkcs8格式，第三條生成RSA公鑰 rsa_public_key.pem
從上面看出經過私鑰能生成對應的公鑰，所以咱們將私鑰private_key.pem用在服務器端，公鑰發放給android跟ios等前端服務器

代碼中的使用app

首先咱們須要封裝寫個RSA的工具類，方便加密解密的操做。ide

package com.example.rsa;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.math.BigInteger;
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.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.RSAPublicKeySpec;
import java.security.spec.X509EncodedKeySpec;

import javax.crypto.Cipher;

/**
 * @author Mr.Zheng
 * @date 2014年8月22日 下午1:44:23
 */
public final class RSAUtils
{
    private static String RSA = "RSA";

    /**
     * 隨機生成RSA密鑰對(默認密鑰長度爲1024)
     * 
     * @return
     */
    public static KeyPair generateRSAKeyPair()
    {
        return generateRSAKeyPair(1024);
    }

    /**
     * 隨機生成RSA密鑰對
     * 
     * @param keyLength
     *            密鑰長度，範圍：512～2048<br>
     *            通常1024
     * @return
     */
    public static KeyPair generateRSAKeyPair(int keyLength)
    {
        try
        {
            KeyPairGenerator kpg = KeyPairGenerator.getInstance(RSA);
            kpg.initialize(keyLength);
            return kpg.genKeyPair();
        } catch (NoSuchAlgorithmException e)
        {
            e.printStackTrace();
            return null;
        }
    }

    /**
     * 用公鑰加密 <br>
     * 每次加密的字節數，不能超過密鑰的長度值減去11
     * 
     * @param data
     *            需加密數據的byte數據
     * @param pubKey
     *            公鑰
     * @return 加密後的byte型數據
     */
    public static byte[] encryptData(byte[] data, PublicKey publicKey)
    {
        try
        {
            Cipher cipher = Cipher.getInstance(RSA);
            // 編碼前設定編碼方式及密鑰
            cipher.init(Cipher.ENCRYPT_MODE, publicKey);
            // 傳入編碼數據並返回編碼結果
            return cipher.doFinal(data);
        } catch (Exception e)
        {
            e.printStackTrace();
            return null;
        }
    }

    /**
     * 用私鑰解密
     * 
     * @param encryptedData
     *            通過encryptedData()加密返回的byte數據
     * @param privateKey
     *            私鑰
     * @return
     */
    public static byte[] decryptData(byte[] encryptedData, PrivateKey privateKey)
    {
        try
        {
            Cipher cipher = Cipher.getInstance(RSA);
            cipher.init(Cipher.DECRYPT_MODE, privateKey);
            return cipher.doFinal(encryptedData);
        } catch (Exception e)
        {
            return null;
        }
    }

    /**
     * 經過公鑰byte[](publicKey.getEncoded())將公鑰還原，適用於RSA算法
     * 
     * @param keyBytes
     * @return
     * @throws NoSuchAlgorithmException
     * @throws InvalidKeySpecException
     */
    public static PublicKey getPublicKey(byte[] keyBytes) throws NoSuchAlgorithmException,
            InvalidKeySpecException
    {
        X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(RSA);
        PublicKey publicKey = keyFactory.generatePublic(keySpec);
        return publicKey;
    }

    /**
     * 經過私鑰byte[]將公鑰還原，適用於RSA算法
     * 
     * @param keyBytes
     * @return
     * @throws NoSuchAlgorithmException
     * @throws InvalidKeySpecException
     */
    public static PrivateKey getPrivateKey(byte[] keyBytes) throws NoSuchAlgorithmException,
            InvalidKeySpecException
    {
        PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(RSA);
        PrivateKey privateKey = keyFactory.generatePrivate(keySpec);
        return privateKey;
    }

    /**
     * 使用N、e值還原公鑰
     * 
     * @param modulus
     * @param publicExponent
     * @return
     * @throws NoSuchAlgorithmException
     * @throws InvalidKeySpecException
     */
    public static PublicKey getPublicKey(String modulus, String publicExponent)
            throws NoSuchAlgorithmException, InvalidKeySpecException
    {
        BigInteger bigIntModulus = new BigInteger(modulus);
        BigInteger bigIntPrivateExponent = new BigInteger(publicExponent);
        RSAPublicKeySpec keySpec = new RSAPublicKeySpec(bigIntModulus, bigIntPrivateExponent);
        KeyFactory keyFactory = KeyFactory.getInstance(RSA);
        PublicKey publicKey = keyFactory.generatePublic(keySpec);
        return publicKey;
    }

    /**
     * 使用N、d值還原私鑰
     * 
     * @param modulus
     * @param privateExponent
     * @return
     * @throws NoSuchAlgorithmException
     * @throws InvalidKeySpecException
     */
    public static PrivateKey getPrivateKey(String modulus, String privateExponent)
            throws NoSuchAlgorithmException, InvalidKeySpecException
    {
        BigInteger bigIntModulus = new BigInteger(modulus);
        BigInteger bigIntPrivateExponent = new BigInteger(privateExponent);
        RSAPublicKeySpec keySpec = new RSAPublicKeySpec(bigIntModulus, bigIntPrivateExponent);
        KeyFactory keyFactory = KeyFactory.getInstance(RSA);
        PrivateKey privateKey = keyFactory.generatePrivate(keySpec);
        return privateKey;
    }

    /**
     * 從字符串中加載公鑰
     * 
     * @param publicKeyStr
     *            公鑰數據字符串
     * @throws Exception
     *             加載公鑰時產生的異常
     */
    public static PublicKey loadPublicKey(String publicKeyStr) throws Exception
    {
        try
        {
            byte[] buffer = Base64Utils.decode(publicKeyStr);
            KeyFactory keyFactory = KeyFactory.getInstance(RSA);
            X509EncodedKeySpec keySpec = new X509EncodedKeySpec(buffer);
            return (RSAPublicKey) keyFactory.generatePublic(keySpec);
        } catch (NoSuchAlgorithmException e)
        {
            throw new Exception("無此算法");
        } catch (InvalidKeySpecException e)
        {
            throw new Exception("公鑰非法");
        } catch (NullPointerException e)
        {
            throw new Exception("公鑰數據爲空");
        }
    }

    /**
     * 從字符串中加載私鑰<br>
     * 加載時使用的是PKCS8EncodedKeySpec（PKCS#8編碼的Key指令）。
     * 
     * @param privateKeyStr
     * @return
     * @throws Exception
     */
    public static PrivateKey loadPrivateKey(String privateKeyStr) throws Exception
    {
        try
        {
            byte[] buffer = Base64Utils.decode(privateKeyStr);
            // X509EncodedKeySpec keySpec = new X509EncodedKeySpec(buffer);
            PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(buffer);
            KeyFactory keyFactory = KeyFactory.getInstance(RSA);
            return (RSAPrivateKey) keyFactory.generatePrivate(keySpec);
        } catch (NoSuchAlgorithmException e)
        {
            throw new Exception("無此算法");
        } catch (InvalidKeySpecException e)
        {
            throw new Exception("私鑰非法");
        } catch (NullPointerException e)
        {
            throw new Exception("私鑰數據爲空");
        }
    }

    /**
     * 從文件中輸入流中加載公鑰
     * 
     * @param in
     *            公鑰輸入流
     * @throws Exception
     *             加載公鑰時產生的異常
     */
    public static PublicKey loadPublicKey(InputStream in) throws Exception
    {
        try
        {
            return loadPublicKey(readKey(in));
        } catch (IOException e)
        {
            throw new Exception("公鑰數據流讀取錯誤");
        } catch (NullPointerException e)
        {
            throw new Exception("公鑰輸入流爲空");
        }
    }

    /**
     * 從文件中加載私鑰
     * 
     * @param keyFileName
     *            私鑰文件名
     * @return 是否成功
     * @throws Exception
     */
    public static PrivateKey loadPrivateKey(InputStream in) throws Exception
    {
        try
        {
            return loadPrivateKey(readKey(in));
        } catch (IOException e)
        {
            throw new Exception("私鑰數據讀取錯誤");
        } catch (NullPointerException e)
        {
            throw new Exception("私鑰輸入流爲空");
        }
    }

    /**
     * 讀取密鑰信息
     * 
     * @param in
     * @return
     * @throws IOException
     */
    private static String readKey(InputStream in) throws IOException
    {
        BufferedReader br = new BufferedReader(new InputStreamReader(in));
        String readLine = null;
        StringBuilder sb = new StringBuilder();
        while ((readLine = br.readLine()) != null)
        {
            if (readLine.charAt(0) == '-')
            {
                continue;
            } else
            {
                sb.append(readLine);
                sb.append('\r');
            }
        }

        return sb.toString();
    }

    /**
     * 打印公鑰信息
     * 
     * @param publicKey
     */
    public static void printPublicKeyInfo(PublicKey publicKey)
    {
        RSAPublicKey rsaPublicKey = (RSAPublicKey) publicKey;
        System.out.println("----------RSAPublicKey----------");
        System.out.println("Modulus.length=" + rsaPublicKey.getModulus().bitLength());
        System.out.println("Modulus=" + rsaPublicKey.getModulus().toString());
        System.out.println("PublicExponent.length=" + rsaPublicKey.getPublicExponent().bitLength());
        System.out.println("PublicExponent=" + rsaPublicKey.getPublicExponent().toString());
    }

    public static void printPrivateKeyInfo(PrivateKey privateKey)
    {
        RSAPrivateKey rsaPrivateKey = (RSAPrivateKey) privateKey;
        System.out.println("----------RSAPrivateKey ----------");
        System.out.println("Modulus.length=" + rsaPrivateKey.getModulus().bitLength());
        System.out.println("Modulus=" + rsaPrivateKey.getModulus().toString());
        System.out.println("PrivateExponent.length=" + rsaPrivateKey.getPrivateExponent().bitLength());
        System.out.println("PrivatecExponent=" + rsaPrivateKey.getPrivateExponent().toString());

    }

}

上面須要注意的就是加密是有長度限制的，過長的話會拋異常！！！

代碼中有些須要使用Base64再轉換的，而java中不自帶，Android中自帶，因此本身寫出一個來，方便Java後臺使用

package com.example.rsa;

import java.io.UnsupportedEncodingException;

/**
 * @author Mr.Zheng
 * @date 2014年8月22日 下午9:50:28
 */
public class Base64Utils
{
    private static char[] base64EncodeChars = new char[]
    { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T',
            'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
            'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5',
            '6', '7', '8', '9', '+', '/' };
    private static byte[] base64DecodeChars = new byte[]
    { -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, 52, 53,
            54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,
            12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, -1, 26, 27, 28, 29,
            30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1,
            -1, -1, -1 };

    /**
     * 加密
     * 
     * @param data
     * @return
     */
    public static String encode(byte[] data)
    {
        StringBuffer sb = new StringBuffer();
        int len = data.length;
        int i = 0;
        int b1, b2, b3;
        while (i < len)
        {
            b1 = data[i++] & 0xff;
            if (i == len)
            {
                sb.append(base64EncodeChars[b1 >>> 2]);
                sb.append(base64EncodeChars[(b1 & 0x3) << 4]);
                sb.append("==");
                break;
            }
            b2 = data[i++] & 0xff;
            if (i == len)
            {
                sb.append(base64EncodeChars[b1 >>> 2]);
                sb.append(base64EncodeChars[((b1 & 0x03) << 4) | ((b2 & 0xf0) >>> 4)]);
                sb.append(base64EncodeChars[(b2 & 0x0f) << 2]);
                sb.append("=");
                break;
            }
            b3 = data[i++] & 0xff;
            sb.append(base64EncodeChars[b1 >>> 2]);
            sb.append(base64EncodeChars[((b1 & 0x03) << 4) | ((b2 & 0xf0) >>> 4)]);
            sb.append(base64EncodeChars[((b2 & 0x0f) << 2) | ((b3 & 0xc0) >>> 6)]);
            sb.append(base64EncodeChars[b3 & 0x3f]);
        }
        return sb.toString();
    }

    /**
     * 解密
     * 
     * @param str
     * @return
     */
    public static byte[] decode(String str)
    {
        try
        {
            return decodePrivate(str);
        } catch (UnsupportedEncodingException e)
        {
            e.printStackTrace();
        }
        return new byte[]
        {};
    }

    private static byte[] decodePrivate(String str) throws UnsupportedEncodingException
    {
        StringBuffer sb = new StringBuffer();
        byte[] data = null;
        data = str.getBytes("US-ASCII");
        int len = data.length;
        int i = 0;
        int b1, b2, b3, b4;
        while (i < len)
        {

            do
            {
                b1 = base64DecodeChars[data[i++]];
            } while (i < len && b1 == -1);
            if (b1 == -1)
                break;

            do
            {
                b2 = base64DecodeChars[data[i++]];
            } while (i < len && b2 == -1);
            if (b2 == -1)
                break;
            sb.append((char) ((b1 << 2) | ((b2 & 0x30) >>> 4)));

            do
            {
                b3 = data[i++];
                if (b3 == 61)
                    return sb.toString().getBytes("iso8859-1");
                b3 = base64DecodeChars[b3];
            } while (i < len && b3 == -1);
            if (b3 == -1)
                break;
            sb.append((char) (((b2 & 0x0f) << 4) | ((b3 & 0x3c) >>> 2)));

            do
            {
                b4 = data[i++];
                if (b4 == 61)
                    return sb.toString().getBytes("iso8859-1");
                b4 = base64DecodeChars[b4];
            } while (i < len && b4 == -1);
            if (b4 == -1)
                break;
            sb.append((char) (((b3 & 0x03) << 6) | b4));
        }
        return sb.toString().getBytes("iso8859-1");
    }

}

最後就是真正使用它們了：

package com.example.rsa;

import java.io.InputStream;
import java.security.PrivateKey;
import java.security.PublicKey;

import android.app.Activity;
import android.os.Bundle;
import android.util.Base64;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;

public class MainActivity extends Activity implements OnClickListener
{
    private Button btn1, btn2;// 加密，解密
    private EditText et1, et2, et3;// 需加密的內容，加密後的內容，解密後的內容

    /* 密鑰內容 base64 code */
    private static String PUCLIC_KEY = "MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCfRTdcPIH10gT9f31rQuIInLwe"
            + "\r" + "7fl2dtEJ93gTmjE9c2H+kLVENWgECiJVQ5sonQNfwToMKdO0b3Olf4pgBKeLThra" + "\r"
            + "z/L3nYJYlbqjHC3jTjUnZc0luumpXGsox62+PuSGBlfb8zJO6hix4GV/vhyQVCpG" + "\r"
            + "9aYqgE7zyTRZYX9byQIDAQAB" + "\r";
    private static String PRIVATE_KEY = "MIICdwIBADANBgkqhkiG9w0BAQEFAASCAmEwggJdAgEAAoGBAJ9FN1w8gfXSBP1/"
            + "\r" + "fWtC4gicvB7t+XZ20Qn3eBOaMT1zYf6QtUQ1aAQKIlVDmyidA1/BOgwp07Rvc6V/" + "\r"
            + "imAEp4tOGtrP8vedgliVuqMcLeNONSdlzSW66alcayjHrb4+5IYGV9vzMk7qGLHg" + "\r"
            + "ZX++HJBUKkb1piqATvPJNFlhf1vJAgMBAAECgYA736xhG0oL3EkN9yhx8zG/5RP/" + "\r"
            + "WJzoQOByq7pTPCr4m/Ch30qVerJAmoKvpPumN+h1zdEBk5PHiAJkm96sG/PTndEf" + "\r"
            + "kZrAJ2hwSBqptcABYk6ED70gRTQ1S53tyQXIOSjRBcugY/21qeswS3nMyq3xDEPK" + "\r"
            + "XpdyKPeaTyuK86AEkQJBAM1M7p1lfzEKjNw17SDMLnca/8pBcA0EEcyvtaQpRvaL" + "\r"
            + "n61eQQnnPdpvHamkRBcOvgCAkfwa1uboru0QdXii/gUCQQDGmkP+KJPX9JVCrbRt" + "\r"
            + "7wKyIemyNM+J6y1ZBZ2bVCf9jacCQaSkIWnIR1S9UM+1CFE30So2CA0CfCDmQy+y" + "\r"
            + "7A31AkB8cGFB7j+GTkrLP7SX6KtRboAU7E0q1oijdO24r3xf/Imw4Cy0AAIx4KAu" + "\r"
            + "L29GOp1YWJYkJXCVTfyZnRxXHxSxAkEAvO0zkSv4uI8rDmtAIPQllF8+eRBT/deD" + "\r"
            + "JBR7ga/k+wctwK/Bd4Fxp9xzeETP0l8/I+IOTagK+Dos8d8oGQUFoQJBAI4Nwpfo" + "\r"
            + "MFaLJXGY9ok45wXrcqkJgM+SN6i8hQeujXESVHYatAIL/1DgLi+u46EFD69fw0w+" + "\r" + "c7o0HLlMsYPAzJw="
            + "\r";

    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initView();
    }

    private void initView()
    {
        btn1 = (Button) findViewById(R.id.btn1);
        btn2 = (Button) findViewById(R.id.btn2);
        btn1.setOnClickListener(this);
        btn2.setOnClickListener(this);

        et1 = (EditText) findViewById(R.id.et1);
        et2 = (EditText) findViewById(R.id.et2);
        et3 = (EditText) findViewById(R.id.et3);
    }

    @Override
    public void onClick(View v)
    {
        switch (v.getId())
        {
        // 加密
        case R.id.btn1:
            String source = et1.getText().toString().trim();
            try
            {
                // 從字符串中獲得公鑰
                // PublicKey publicKey = RSAUtils.loadPublicKey(PUCLIC_KEY);
                // 從文件中獲得公鑰
                InputStream inPublic = getResources().getAssets().open("rsa_public_key.pem");
                PublicKey publicKey = RSAUtils.loadPublicKey(inPublic);
                // 加密
                byte[] encryptByte = RSAUtils.encryptData(source.getBytes(), publicKey);
                // 爲了方便觀察吧加密後的數據用base64加密轉一下，要否則看起來是亂碼,因此解密是也是要用Base64先轉換
                String afterencrypt = Base64Utils.encode(encryptByte);
                et2.setText(afterencrypt);
            } catch (Exception e)
            {
                e.printStackTrace();
            }
            break;
        // 解密
        case R.id.btn2:
            String encryptContent = et2.getText().toString().trim();
            try
            {
                // 從字符串中獲得私鑰
                // PrivateKey privateKey = RSAUtils.loadPrivateKey(PRIVATE_KEY);
                // 從文件中獲得私鑰
                InputStream inPrivate = getResources().getAssets().open("pkcs8_rsa_private_key.pem");
                PrivateKey privateKey = RSAUtils.loadPrivateKey(inPrivate);
                // 由於RSA加密後的內容經Base64再加密轉換了一下，因此先Base64解密回來再給RSA解密
                byte[] decryptByte = RSAUtils.decryptData(Base64Utils.decode(encryptContent), privateKey);
                String decryptStr = new String(decryptByte);
                et3.setText(decryptStr);
            } catch (Exception e)
            {
                e.printStackTrace();
            }
            break;
        default:
            break;
        }
    }

}

我把密鑰放到assest資源文件夾裏了，也能夠直接使用字符串獲得，上面註釋掉了。

後記：後來發現，android的rsa機制和php，java的默認機制有點不一樣

也就是說android系統的RSA實現是"RSA/None/NoPadding"，而標準JDK實現是"RSA/ECB/PKCS1Padding"

具體解決方法http://stackoverflow.com/questions/13556295/rsa-encryption-in-android

稍微做修改一下這裏：Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");就好了

修改後的RSAUtils類

package com.example.rsa;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.math.BigInteger;
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.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.RSAPublicKeySpec;
import java.security.spec.X509EncodedKeySpec;

import javax.crypto.Cipher;

/**
 * @author Mr.Zheng
 * @date 2014年8月22日 下午1:44:23
 */
public final class RSAUtils
{
    private static String RSA = "RSA";
    private static String RSA1 = "RSA/ECB/PKCS1Padding";
    /**
     * 隨機生成RSA密鑰對(默認密鑰長度爲1024)
     * 
     * @return
     */
    public static KeyPair generateRSAKeyPair()
    {
        return generateRSAKeyPair(1024);
    }

    /**
     * 隨機生成RSA密鑰對
     * 
     * @param keyLength
     *            密鑰長度，範圍：512～2048<br>
     *            通常1024
     * @return
     */
    public static KeyPair generateRSAKeyPair(int keyLength)
    {
        try
        {
            KeyPairGenerator kpg = KeyPairGenerator.getInstance(RSA);
            kpg.initialize(keyLength);
            return kpg.genKeyPair();
        } catch (NoSuchAlgorithmException e)
        {
            e.printStackTrace();
            return null;
        }
    }

    /**
     * 用公鑰加密 <br>
     * 每次加密的字節數，不能超過密鑰的長度值減去11
     * 
     * @param data
     *            需加密數據的byte數據
     * @param pubKey
     *            公鑰
     * @return 加密後的byte型數據
     */
    public static byte[] encryptData(byte[] data, PublicKey publicKey)
    {
        try
        {
            Cipher cipher = Cipher.getInstance(RSA1);
            // 編碼前設定編碼方式及密鑰
            cipher.init(Cipher.ENCRYPT_MODE, publicKey);
            // 傳入編碼數據並返回編碼結果
            return cipher.doFinal(data);
        } catch (Exception e)
        {
            e.printStackTrace();
            return null;
        }
    }

    /**
     * 用私鑰解密
     * 
     * @param encryptedData
     *            通過encryptedData()加密返回的byte數據
     * @param privateKey
     *            私鑰
     * @return
     */
    public static byte[] decryptData(byte[] encryptedData, PrivateKey privateKey)
    {
        try
        {
            Cipher cipher = Cipher.getInstance(RSA1);
            cipher.init(Cipher.DECRYPT_MODE, privateKey);
            return cipher.doFinal(encryptedData);
        } catch (Exception e)
        {
            return null;
        }
    }

    /**
     * 經過公鑰byte[](publicKey.getEncoded())將公鑰還原，適用於RSA算法
     * 
     * @param keyBytes
     * @return
     * @throws NoSuchAlgorithmException
     * @throws InvalidKeySpecException
     */
    public static PublicKey getPublicKey(byte[] keyBytes) throws NoSuchAlgorithmException,
            InvalidKeySpecException
    {
        X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(RSA);
        PublicKey publicKey = keyFactory.generatePublic(keySpec);
        return publicKey;
    }

    /**
     * 經過私鑰byte[]將公鑰還原，適用於RSA算法
     * 
     * @param keyBytes
     * @return
     * @throws NoSuchAlgorithmException
     * @throws InvalidKeySpecException
     */
    public static PrivateKey getPrivateKey(byte[] keyBytes) throws NoSuchAlgorithmException,
            InvalidKeySpecException
    {
        PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(RSA);
        PrivateKey privateKey = keyFactory.generatePrivate(keySpec);
        return privateKey;
    }

    /**
     * 使用N、e值還原公鑰
     * 
     * @param modulus
     * @param publicExponent
     * @return
     * @throws NoSuchAlgorithmException
     * @throws InvalidKeySpecException
     */
    public static PublicKey getPublicKey(String modulus, String publicExponent)
            throws NoSuchAlgorithmException, InvalidKeySpecException
    {
        BigInteger bigIntModulus = new BigInteger(modulus);
        BigInteger bigIntPrivateExponent = new BigInteger(publicExponent);
        RSAPublicKeySpec keySpec = new RSAPublicKeySpec(bigIntModulus, bigIntPrivateExponent);
        KeyFactory keyFactory = KeyFactory.getInstance(RSA);
        PublicKey publicKey = keyFactory.generatePublic(keySpec);
        return publicKey;
    }

    /**
     * 使用N、d值還原私鑰
     * 
     * @param modulus
     * @param privateExponent
     * @return
     * @throws NoSuchAlgorithmException
     * @throws InvalidKeySpecException
     */
    public static PrivateKey getPrivateKey(String modulus, String privateExponent)
            throws NoSuchAlgorithmException, InvalidKeySpecException
    {
        BigInteger bigIntModulus = new BigInteger(modulus);
        BigInteger bigIntPrivateExponent = new BigInteger(privateExponent);
        RSAPublicKeySpec keySpec = new RSAPublicKeySpec(bigIntModulus, bigIntPrivateExponent);
        KeyFactory keyFactory = KeyFactory.getInstance(RSA);
        PrivateKey privateKey = keyFactory.generatePrivate(keySpec);
        return privateKey;
    }

    /**
     * 從字符串中加載公鑰
     * 
     * @param publicKeyStr
     *            公鑰數據字符串
     * @throws Exception
     *             加載公鑰時產生的異常
     */
    public static PublicKey loadPublicKey(String publicKeyStr) throws Exception
    {
        try
        {
            byte[] buffer = Base64Utils.decode(publicKeyStr);
            KeyFactory keyFactory = KeyFactory.getInstance(RSA);
            X509EncodedKeySpec keySpec = new X509EncodedKeySpec(buffer);
            return (RSAPublicKey) keyFactory.generatePublic(keySpec);
        } catch (NoSuchAlgorithmException e)
        {
            throw new Exception("無此算法");
        } catch (InvalidKeySpecException e)
        {
            throw new Exception("公鑰非法");
        } catch (NullPointerException e)
        {
            throw new Exception("公鑰數據爲空");
        }
    }

    /**
     * 從字符串中加載私鑰<br>
     * 加載時使用的是PKCS8EncodedKeySpec（PKCS#8編碼的Key指令）。
     * 
     * @param privateKeyStr
     * @return
     * @throws Exception
     */
    public static PrivateKey loadPrivateKey(String privateKeyStr) throws Exception
    {
        try
        {
            byte[] buffer = Base64Utils.decode(privateKeyStr);
            // X509EncodedKeySpec keySpec = new X509EncodedKeySpec(buffer);
            PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(buffer);
            KeyFactory keyFactory = KeyFactory.getInstance(RSA);
            return (RSAPrivateKey) keyFactory.generatePrivate(keySpec);
        } catch (NoSuchAlgorithmException e)
        {
            throw new Exception("無此算法");
        } catch (InvalidKeySpecException e)
        {
            throw new Exception("私鑰非法");
        } catch (NullPointerException e)
        {
            throw new Exception("私鑰數據爲空");
        }
    }

    /**
     * 從文件中輸入流中加載公鑰
     * 
     * @param in
     *            公鑰輸入流
     * @throws Exception
     *             加載公鑰時產生的異常
     */
    public static PublicKey loadPublicKey(InputStream in) throws Exception
    {
        try
        {
            return loadPublicKey(readKey(in));
        } catch (IOException e)
        {
            throw new Exception("公鑰數據流讀取錯誤");
        } catch (NullPointerException e)
        {
            throw new Exception("公鑰輸入流爲空");
        }
    }

    /**
     * 從文件中加載私鑰
     * 
     * @param keyFileName
     *            私鑰文件名
     * @return 是否成功
     * @throws Exception
     */
    public static PrivateKey loadPrivateKey(InputStream in) throws Exception
    {
        try
        {
            return loadPrivateKey(readKey(in));
        } catch (IOException e)
        {
            throw new Exception("私鑰數據讀取錯誤");
        } catch (NullPointerException e)
        {
            throw new Exception("私鑰輸入流爲空");
        }
    }

    /**
     * 讀取密鑰信息
     * 
     * @param in
     * @return
     * @throws IOException
     */
    private static String readKey(InputStream in) throws IOException
    {
        BufferedReader br = new BufferedReader(new InputStreamReader(in));
        String readLine = null;
        StringBuilder sb = new StringBuilder();
        while ((readLine = br.readLine()) != null)
        {
            if (readLine.charAt(0) == '-')
            {
                continue;
            } else
            {
                sb.append(readLine);
                sb.append('\r');
            }
        }

        return sb.toString();
    }

    /**
     * 打印公鑰信息
     * 
     * @param publicKey
     */
    public static void printPublicKeyInfo(PublicKey publicKey)
    {
        RSAPublicKey rsaPublicKey = (RSAPublicKey) publicKey;
        System.out.println("----------RSAPublicKey----------");
        System.out.println("Modulus.length=" + rsaPublicKey.getModulus().bitLength());
        System.out.println("Modulus=" + rsaPublicKey.getModulus().toString());
        System.out.println("PublicExponent.length=" + rsaPublicKey.getPublicExponent().bitLength());
        System.out.println("PublicExponent=" + rsaPublicKey.getPublicExponent().toString());
    }

    public static void printPrivateKeyInfo(PrivateKey privateKey)
    {
        RSAPrivateKey rsaPrivateKey = (RSAPrivateKey) privateKey;
        System.out.println("----------RSAPrivateKey ----------");
        System.out.println("Modulus.length=" + rsaPrivateKey.getModulus().bitLength());
        System.out.println("Modulus=" + rsaPrivateKey.getModulus().toString());
        System.out.println("PrivateExponent.length=" + rsaPrivateKey.getPrivateExponent().bitLength());
        System.out.println("PrivatecExponent=" + rsaPrivateKey.getPrivateExponent().toString());

    }

}

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