利用RSA加密算法 生成公私鑰進行加解密

首先需求是公司需要對登錄接口進行升級，由原來的單線加解密改爲非對稱加密以及前端記住密碼的功能
由於不瞭解，於是大概搜索了一下，在此進行整理。主要是一些工具類
隨便一搜，最多的就是基於RSA進行公私鑰加解密

先說下準備工具，工具類

package com.hqjl.classcard.utils;

import javax.crypto.Cipher;
import java.io.ByteArrayOutputStream;
import java.security.*;
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;

/**
 * @author chunying
 * @Date: 2019/9/10 0010
 */
public class RSAUtils {



    /** */
    /**
     * 加密算法RSA
     */
    public static final String KEY_ALGORITHM = "RSA";

    /** */
    /**
     * 簽名算法
     */
    public static final String SIGNATURE_ALGORITHM = "MD5withRSA";

    /** */
    /**
     * 獲取公鑰的key
     */
    private static final String PUBLIC_KEY = "RSAPublicKey";

    /** */
    /**
     * 獲取私鑰的key
     */
    private static final String PRIVATE_KEY = "RSAPrivateKey";

    /** */
    /**
     * RSA最大加密明文大小
     */
    private static final int MAX_ENCRYPT_BLOCK = 117;

    /** */
    /**
     * RSA最大解密密文大小
     */
    private static final int MAX_DECRYPT_BLOCK = 128;

    /** */
    /**
     * <p>
     * 生成密鑰對(公鑰和私鑰)
     * </p>
     *
     * @return
     * @throws Exception
     */
    public static Map<String, Object> genKeyPair() throws Exception {
        KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance(KEY_ALGORITHM);
        keyPairGen.initialize(1024);
        KeyPair keyPair = keyPairGen.generateKeyPair();
        RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
        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;
    }

    /** */
    /**
     * <p>
     * 用私鑰對信息生成數字簽名
     * </p>
     *
     * @param data
     *            已加密數據
     * @param privateKey
     *            私鑰(BASE64編碼)
     *
     * @return
     * @throws Exception
     */
    public static String sign(byte[] data, String privateKey) throws Exception {
        byte[] keyBytes = Base64Utils.decode(privateKey);
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        PrivateKey privateK = keyFactory.generatePrivate(pkcs8KeySpec);
        Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
        signature.initSign(privateK);
        signature.update(data);
        return Base64Utils.encode(signature.sign());
    }

    /** */
    /**
     * <p>
     * 校驗數字簽名
     * </p>
     *
     * @param data
     *            已加密數據
     * @param publicKey
     *            公鑰(BASE64編碼)
     * @param sign
     *            數字簽名
     *
     * @return
     * @throws Exception
     *
     */
    public static boolean verify(byte[] data, String publicKey, String sign) throws Exception {
        byte[] keyBytes = Base64Utils.decode(publicKey);
        X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        PublicKey publicK = keyFactory.generatePublic(keySpec);
        Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
        signature.initVerify(publicK);
        signature.update(data);
        return signature.verify(Base64Utils.decode(sign));
    }

    /** */
    /**
     * <P>
     * 私鑰解密
     * </p>
     *
     * @param encryptedData
     *            已加密數據
     * @param privateKey
     *            私鑰(BASE64編碼)
     * @return
     * @throws Exception
     */
    public static byte[] decryptByPrivateKey(byte[] encryptedData, String privateKey) throws Exception {
        byte[] keyBytes = Base64Utils.decode(privateKey);
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        Key privateK = keyFactory.generatePrivate(pkcs8KeySpec);
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.DECRYPT_MODE, privateK);
        int inputLen = encryptedData.length;
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        int offSet = 0;
        byte[] cache;
        int i = 0;
        // 對數據分段解密
        while (inputLen - offSet > 0) {
            if (inputLen - offSet > MAX_DECRYPT_BLOCK) {
                cache = cipher.doFinal(encryptedData, offSet, MAX_DECRYPT_BLOCK);
            } else {
                cache = cipher.doFinal(encryptedData, offSet, inputLen - offSet);
            }
            out.write(cache, 0, cache.length);
            i++;
            offSet = i * MAX_DECRYPT_BLOCK;
        }
        byte[] decryptedData = out.toByteArray();
        out.close();
        return decryptedData;
    }

    /** */
    /**
     * <p>
     * 公鑰解密
     * </p>
     *
     * @param encryptedData
     *            已加密數據
     * @param publicKey
     *            公鑰(BASE64編碼)
     * @return
     * @throws Exception
     */
    public static byte[] decryptByPublicKey(byte[] encryptedData, String publicKey) throws Exception {
        byte[] keyBytes = Base64Utils.decode(publicKey);
        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        Key publicK = keyFactory.generatePublic(x509KeySpec);
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.DECRYPT_MODE, publicK);
        int inputLen = encryptedData.length;
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        int offSet = 0;
        byte[] cache;
        int i = 0;
        // 對數據分段解密
        while (inputLen - offSet > 0) {
            if (inputLen - offSet > MAX_DECRYPT_BLOCK) {
                cache = cipher.doFinal(encryptedData, offSet, MAX_DECRYPT_BLOCK);
            } else {
                cache = cipher.doFinal(encryptedData, offSet, inputLen - offSet);
            }
            out.write(cache, 0, cache.length);
            i++;
            offSet = i * MAX_DECRYPT_BLOCK;
        }
        byte[] decryptedData = out.toByteArray();
        out.close();
        return decryptedData;
    }

    /** */
    /**
     * <p>
     * 公鑰加密
     * </p>
     *
     * @param data
     *            源數據
     * @param publicKey
     *            公鑰(BASE64編碼)
     * @return
     * @throws Exception
     */
    public static byte[] encryptByPublicKey(byte[] data, String publicKey) throws Exception {
        byte[] keyBytes = Base64Utils.decode(publicKey);
        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        Key publicK = keyFactory.generatePublic(x509KeySpec);
        // 對數據加密
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.ENCRYPT_MODE, publicK);
        int inputLen = data.length;
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        int offSet = 0;
        byte[] cache;
        int i = 0;
        // 對數據分段加密
        while (inputLen - offSet > 0) {
            if (inputLen - offSet > MAX_ENCRYPT_BLOCK) {
                cache = cipher.doFinal(data, offSet, MAX_ENCRYPT_BLOCK);
            } else {
                cache = cipher.doFinal(data, offSet, inputLen - offSet);
            }
            out.write(cache, 0, cache.length);
            i++;
            offSet = i * MAX_ENCRYPT_BLOCK;
        }
        byte[] encryptedData = out.toByteArray();
        out.close();
        return encryptedData;
    }

    /** */
    /**
     * <p>
     * 私鑰加密
     * </p>
     *
     * @param data
     *            源數據
     * @param privateKey
     *            私鑰(BASE64編碼)
     * @return
     * @throws Exception
     */
    public static byte[] encryptByPrivateKey(byte[] data, String privateKey) throws Exception {
        byte[] keyBytes = Base64Utils.decode(privateKey);
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        Key privateK = keyFactory.generatePrivate(pkcs8KeySpec);
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.ENCRYPT_MODE, privateK);
        int inputLen = data.length;
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        int offSet = 0;
        byte[] cache;
        int i = 0;
        // 對數據分段加密
        while (inputLen - offSet > 0) {
            if (inputLen - offSet > MAX_ENCRYPT_BLOCK) {
                cache = cipher.doFinal(data, offSet, MAX_ENCRYPT_BLOCK);
            } else {
                cache = cipher.doFinal(data, offSet, inputLen - offSet);
            }
            out.write(cache, 0, cache.length);
            i++;
            offSet = i * MAX_ENCRYPT_BLOCK;
        }
        byte[] encryptedData = out.toByteArray();
        out.close();
        return encryptedData;
    }

    /** */
    /**
     * <p>
     * 獲取私鑰
     * </p>
     *
     * @param keyMap
     *            密鑰對
     * @return
     * @throws Exception
     */
    public static String getPrivateKey(Map<String, Object> keyMap) throws Exception {
        Key key = (Key) keyMap.get(PRIVATE_KEY);
        return Base64Utils.encode(key.getEncoded());
    }

    /** */
    /**
     * <p>
     * 獲取公鑰
     * </p>
     *
     * @param keyMap
     *            密鑰對
     * @return
     * @throws Exception
     */
    public static String getPublicKey(Map<String, Object> keyMap) throws Exception {
        Key key = (Key) keyMap.get(PUBLIC_KEY);
        return com.hqjl.classcard.utils.Base64Utils.encode(key.getEncoded());
    }

    /**
     * java端公鑰加密
     */
    public static String encryptedDataOnJava(String data, String PUBLICKEY) {
        try {
            data = Base64Utils.encode(encryptByPublicKey(data.getBytes(), PUBLICKEY));
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return data;
    }

    /**
     * java端私鑰解密
     */
    public static String decryptDataOnJava(String data, String PRIVATEKEY) {
        String temp = "";
        try {
            byte[] rs = Base64Utils.decode(data);
            temp = new String(RSAUtils.decryptByPrivateKey(rs, PRIVATEKEY),"UTF-8"); //以utf-8的方式生成字符串

        } catch (Exception e) {
            e.printStackTrace();
        }
        return temp;
    }
}


package com.hqjl.classcard.utils;

import com.itextpdf.xmp.impl.Base64;

import java.io.*;

/**
 * @author chunying
 * @Date: 2019/9/11 0011
 */
public class Base64Utils {




    /** */
    /**
     * 文件讀取緩衝區大小
     */
    private static final int CACHE_SIZE = 1024;

    /** */
    /**
     * <p>
     * BASE64字符串解碼爲二進制數據
     * </p>
     *
     * @param base64
     * @return
     * @throws Exception
     */
    public static byte[] decode(String base64) throws Exception {
        return Base64.decode(base64.getBytes());
    }

    /** */
    /**
     * <p>
     * 二進制數據編碼爲BASE64字符串
     * </p>
     *
     * @param bytes
     * @return
     * @throws Exception
     */
    public static String encode(byte[] bytes) throws Exception {
        return new String(Base64.encode(bytes));
    }

    /** */
    /**
     * <p>
     * 將文件編碼爲BASE64字符串
     * </p>
     * <p>
     * 大文件慎用，可能會導致內存溢出
     * </p>
     *
     * @param filePath
     *            文件絕對路徑
     * @return
     * @throws Exception
     */
    public static String encodeFile(String filePath) throws Exception {
        byte[] bytes = fileToByte(filePath);
        return encode(bytes);
    }

    /** */
    /**
     * <p>
     * BASE64字符串轉回文件
     * </p>
     *
     * @param filePath
     *            文件絕對路徑
     * @param base64
     *            編碼字符串
     * @throws Exception
     */
    public static void decodeToFile(String filePath, String base64) throws Exception {
        byte[] bytes = decode(base64);
        byteArrayToFile(bytes, filePath);
    }

    /** */
    /**
     * <p>
     * 文件轉換爲二進制數組
     * </p>
     *
     * @param filePath
     *            文件路徑
     * @return
     * @throws Exception
     */
    public static byte[] fileToByte(String filePath) throws Exception {
        byte[] data = new byte[0];
        File file = new File(filePath);
        if (file.exists()) {
            FileInputStream in = new FileInputStream(file);
            ByteArrayOutputStream out = new ByteArrayOutputStream(2048);
            byte[] cache = new byte[CACHE_SIZE];
            int nRead = 0;
            while ((nRead = in.read(cache)) != -1) {
                out.write(cache, 0, nRead);
                out.flush();
            }
            out.close();
            in.close();
            data = out.toByteArray();
        }
        return data;
    }

    /** */
    /**
     * <p>
     * 二進制數據寫文件
     * </p>
     *
     * @param bytes
     *            二進制數據
     * @param filePath
     *            文件生成目錄
     */
    public static void byteArrayToFile(byte[] bytes, String filePath) throws Exception {
        InputStream in = new ByteArrayInputStream(bytes);
        File destFile = new File(filePath);
        if (!destFile.getParentFile().exists()) {
            destFile.getParentFile().mkdirs();
        }
        destFile.createNewFile();
        OutputStream out = new FileOutputStream(destFile);
        byte[] cache = new byte[CACHE_SIZE];
        int nRead = 0;
        while ((nRead = in.read(cache)) != -1) {
            out.write(cache, 0, nRead);
            out.flush();
        }
        out.close();
        in.close();
    }
}

之所以要用Base64壓縮，是因爲RSA生成的公私鑰以及加解密生成的字符串是二進制的 需要壓縮後能正常顯示及傳輸

因爲公鑰是比私鑰短好多的，一般都是前端用公鑰加密，後臺用私鑰解密，注意每次加密生成的字符串都是不一樣的。

大致用法是：（後臺爲截取代碼）
前臺先向獲取公鑰
然後用js方法進行加密後傳給後臺（注意，此時已被base壓縮）
後臺
encryptedPwd爲從前臺獲取的加密密碼

 byte[] decodedData;
        try {
            decodedData = RSAUtils.decryptByPrivateKey(Base64Utils.decode(encryptedPwd), rsaInfo.getPrivateKey());
        }catch(Exception e) {
            logger_.error(e.getMessage(), e);
        }

大致思路就是這樣