RSA算法 JS加密 安卓加密 ios加密 JAVA解密

有这样一个需求，前端登录的用户名密码，密码必需加密，但不可使用MD5，因为后台要检测密码的复杂度，那么在保证安全的前提下将密码传到后台呢，答案就是使用RSA非对称加密算法解决 。

java代码

需要依赖 commons-codec 包
RSACoder.java

import org.apache.commons.codec.binary.Base64;

import javax.crypto.Cipher;
import java.security.*;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;

/**
 * Created by lake on 17-4-12.
 */
public class RSACoder {
    public static final String KEY_ALGORITHM = "RSA";
    public static final String SIGNATURE_ALGORITHM = "MD5withRSA";

    private static final String PUBLIC_KEY = "RSAPublicKey";
    private static final String PRIVATE_KEY = "RSAPrivateKey";

    public static byte[] decryptBASE64(String key) {
        return Base64.decodeBase64(key);
    }

    public static String encryptBASE64(byte[] bytes) {
        return Base64.encodeBase64String(bytes);
    }

    /**
     * 用私钥对信息生成数字签名
     *
     * @param data       加密数据
     * @param privateKey 私钥
     * @return
     * @throws Exception
     */
    public static String sign(byte[] data, String privateKey) throws Exception {
        // 解密由base64编码的私钥
        byte[] keyBytes = decryptBASE64(privateKey);
        // 构造PKCS8EncodedKeySpec对象
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
        // KEY_ALGORITHM 指定的加密算法
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        // 取私钥匙对象
        PrivateKey priKey = keyFactory.generatePrivate(pkcs8KeySpec);
        // 用私钥对信息生成数字签名
        Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
        signature.initSign(priKey);
        signature.update(data);
        return encryptBASE64(signature.sign());
    }

    /**
     * 校验数字签名
     *
     * @param data      加密数据
     * @param publicKey 公钥
     * @param sign      数字签名
     * @return 校验成功返回true 失败返回false
     * @throws Exception
     */
    public static boolean verify(byte[] data, String publicKey, String sign)
            throws Exception {
        // 解密由base64编码的公钥
        byte[] keyBytes = decryptBASE64(publicKey);
        // 构造X509EncodedKeySpec对象
        X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);
        // KEY_ALGORITHM 指定的加密算法
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        // 取公钥匙对象
        PublicKey pubKey = keyFactory.generatePublic(keySpec);
        Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
        signature.initVerify(pubKey);
        signature.update(data);
        // 验证签名是否正常
        return signature.verify(decryptBASE64(sign));
    }

    public static byte[] decryptByPrivateKey(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(KEY_ALGORITHM);
        Key privateKey = keyFactory.generatePrivate(pkcs8KeySpec);
        // 对数据解密
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.DECRYPT_MODE, privateKey);
        return cipher.doFinal(data);
    }

    /**
     * 解密

     * 用私钥解密
     *
     * @param data
     * @param key
     * @return
     * @throws Exception
     */
    public static byte[] decryptByPrivateKey(String data, String key)
            throws Exception {
        return decryptByPrivateKey(decryptBASE64(data),key);
    }

    /**
     * 解密

     * 用公钥解密
     *
     * @param data
     * @param key
     * @return
     * @throws Exception
     */
    public static byte[] decryptByPublicKey(byte[] data, String key)
            throws Exception {
        // 对密钥解密
        byte[] keyBytes = decryptBASE64(key);
        // 取得公钥
        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        Key publicKey = keyFactory.generatePublic(x509KeySpec);
        // 对数据解密
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.DECRYPT_MODE, publicKey);
        return cipher.doFinal(data);
    }

    /**
     * 加密

     * 用公钥加密
     *
     * @param data
     * @param key
     * @return
     * @throws Exception
     */
    public static byte[] encryptByPublicKey(String 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(KEY_ALGORITHM);
        Key publicKey = keyFactory.generatePublic(x509KeySpec);
        // 对数据加密
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.ENCRYPT_MODE, publicKey);
        return cipher.doFinal(data.getBytes());
    }

    /**
     * 加密

     * 用私钥加密
     *
     * @param data
     * @param key
     * @return
     * @throws Exception
     */
    public static byte[] encryptByPrivateKey(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(KEY_ALGORITHM);
        Key privateKey = keyFactory.generatePrivate(pkcs8KeySpec);
        // 对数据加密
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.ENCRYPT_MODE, privateKey);
        return cipher.doFinal(data);
    }

    /**
     * 取得私钥
     *
     * @param keyMap
     * @return
     * @throws Exception
     */
    public static String getPrivateKey(Map 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 keyMap)
            throws Exception {
        Key key = keyMap.get(PUBLIC_KEY);
        return encryptBASE64(key.getEncoded());
    }

    /**
     * 初始化密钥
     *
     * @return
     * @throws Exception
     */
    public static Map initKey() throws Exception {
        KeyPairGenerator keyPairGen = KeyPairGenerator
                .getInstance(KEY_ALGORITHM);
        keyPairGen.initialize(1024);
        KeyPair keyPair = keyPairGen.generateKeyPair();
        Map keyMap = new HashMap(2);
        keyMap.put(PUBLIC_KEY, keyPair.getPublic());// 公钥
        keyMap.put(PRIVATE_KEY, keyPair.getPrivate());// 私钥
        return keyMap;
    }
}

测试类
RSACoderTest.java

import org.junit.Before;
import org.junit.Test;

import java.security.Key;
import java.util.Map;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue;

/**
 * Created by lake on 17-4-12.
 */
public class RSACoderTest {
    private String publicKey;
    private String privateKey;

    @Before
    public void setUp() throws Exception {
        Map keyMap = RSACoder.initKey();
        publicKey = RSACoder.getPublicKey(keyMap);
        privateKey = RSACoder.getPrivateKey(keyMap);
        System.err.println("公钥: \n\r" + publicKey);
        System.err.println("私钥： \n\r" + privateKey);
    }

    @Test
    public void test() throws Exception {
        System.err.println("公钥加密——私钥解密");
        String inputStr = "abc";
        byte[] encodedData = RSACoder.encryptByPublicKey(inputStr, publicKey);
        byte[] decodedData = RSACoder.decryptByPrivateKey(encodedData,
                privateKey);
        String outputStr = new String(decodedData);
        System.err.println("加密前: " + inputStr + "\n\r" + "解密后: " + outputStr);
        assertEquals(inputStr, outputStr);
    }

    @Test
    public void testSign() throws Exception {
        System.err.println("私钥加密——公钥解密");
        String inputStr = "sign";
        byte[] data = inputStr.getBytes();
        byte[] encodedData = RSACoder.encryptByPrivateKey(data, privateKey);
        byte[] decodedData = RSACoder.decryptByPublicKey(encodedData, publicKey);
        String outputStr = new String(decodedData);
        System.err.println("加密前: " + inputStr + "\n\r" + "解密后: " + outputStr);
        assertEquals(inputStr, outputStr);
        System.err.println("私钥签名——公钥验证签名");
        // 产生签名
        String sign = RSACoder.sign(encodedData, privateKey);
        System.err.println("签名:" + sign);
        // 验证签名
        boolean status = RSACoder.verify(encodedData, publicKey, sign);
        System.err.println("状态:" + status);
        assertTrue(status);
    }
}

前端代码

依赖 jsencrypt 项目

IOS代码

static SecKeyRef _public_key = nil;
        // 从公钥证书文件中获取到公钥的SecKeyRef指针:  @"public_key" ofType:@"der"
        NSString *publicKeyPath = [paramsDict stringValueForKey:@"publicKey" defaultValue:@""];
        publicKeyPath = [self getPathWithUZSchemeURL:publicKeyPath];
        if (![[NSFileManager defaultManager] fileExistsAtPath:publicKeyPath]) {
            [self sendResultEventWithCallbackId:rsaCbId dataDict:@{@"status":[NSNumber numberWithBool:false]} errDict:@{@"code":@(-1)} doDelete:NO];
            return;
        }
        NSData *certificateData = [[NSData alloc]initWithContentsOfFile:publicKeyPath];
        SecCertificateRef myCertificate =  SecCertificateCreateWithData(kCFAllocatorDefault, (CFDataRef)certificateData);
        SecPolicyRef myPolicy = SecPolicyCreateBasicX509();
        SecTrustRef myTrust;
        OSStatus status = SecTrustCreateWithCertificates(myCertificate,myPolicy,&myTrust);
        SecTrustResultType trustResult;
        if (status == noErr) {
            status = SecTrustEvaluate(myTrust, &trustResult);
        }
        _public_key = SecTrustCopyPublicKey(myTrust);
        CFRelease(myCertificate);
        CFRelease(myPolicy);
        CFRelease(myTrust);

        SecKeyRef key = _public_key;
        size_t cipherBufferSize = SecKeyGetBlockSize(key);
        uint8_t *cipherBuffer = malloc(cipherBufferSize * sizeof(uint8_t));
        NSData *stringBytes = [inString dataUsingEncoding:NSUTF8StringEncoding];
        size_t blockSize = cipherBufferSize - 11;
        size_t blockCount = (size_t)ceil([stringBytes length] / (double)blockSize);
        NSMutableData *encryptedData = [[NSMutableData alloc] init];
        NSString *outString = [[NSString alloc] init];
        for (int i=0; i

NSString *password = [paramsDict stringValueForKey:@"password" defaultValue:@""];
    NSString *inString = [paramsDict stringValueForKey:@"data" defaultValue:@""];
    NSString *value = @"";
    if (inString.length <= 0) {
        //err:1
        return value;
    } else {
        // 从私钥证书文件中获取到公钥的SecKeyRef指针:  @"private_key" ofType:@"pem"
        NSString *privateKeyPath = [paramsDict stringValueForKey:@"privateKey" defaultValue:@""];
        privateKeyPath = [self getPathWithUZSchemeURL:privateKeyPath];
        if (![[NSFileManager defaultManager] fileExistsAtPath:privateKeyPath]) {
            return value;
        }
        NSData *p12Data = [[NSData alloc]initWithContentsOfFile:privateKeyPath];
        SecKeyRef privateKeyRef = NULL;
        NSMutableDictionary *options = [[NSMutableDictionary alloc] init];
        [options setObject:password forKey:(__bridge id)kSecImportExportPassphrase];
        CFArrayRef items = CFArrayCreate(NULL, 0, 0, NULL);
        OSStatus securityError = SecPKCS12Import((__bridge CFDataRef) p12Data, (__bridge CFDictionaryRef)options, &items);
        if (securityError == noErr && CFArrayGetCount(items) > 0) {
            CFDictionaryRef identityDict = CFArrayGetValueAtIndex(items, 0);
            SecIdentityRef identityApp = (SecIdentityRef)CFDictionaryGetValue(identityDict, kSecImportItemIdentity);
            securityError = SecIdentityCopyPrivateKey(identityApp, &privateKeyRef);
            if (securityError != noErr) {
                privateKeyRef = NULL;
            }
        } else {
            return value;
        }
        CFRelease(items);
        
        NSData *cipherData = [NSData dataWithBase64EncodedString:inString];
        //        NSData* decryptData = [self rsaDecryptData: data];
        size_t cipherLen = [cipherData length];
        void *cipher = malloc(cipherLen);
        [cipherData getBytes:cipher length:cipherLen];
        size_t plainLen = SecKeyGetBlockSize(privateKeyRef) - 12;
        void *plain = malloc(plainLen);
        OSStatus status = SecKeyDecrypt(privateKeyRef, kSecPaddingPKCS1, cipher, cipherLen, plain, &plainLen);
        if (status != noErr) {
            return value;
        }
        NSData *decryptedData = [[NSData alloc] initWithBytes:(const void *)plain length:plainLen];
        value = [[NSString alloc] initWithData:decryptedData encoding:NSUTF8StringEncoding];
        NSMutableString *outString = [[NSMutableString alloc] init];
        //如果没有进行加密直接解密，outString 将为 nil
        if (!value && decryptedData && decryptedData.length > 0) {
            Byte *datas = (Byte*)[decryptedData bytes];
            outString = [NSMutableString stringWithCapacity:decryptedData.length * 2];
            for(int i = 0; i < decryptedData.length; i++){
                [outString appendFormat:@"%02x", datas[i]];
            }
            value = [outString copy];
        }
        return value;
    }

安卓工具类

/**
 * RSA算法，实现数据的加密解密。 
 */
public class RSAUtil {

    /**
     *  使用私钥解密
     * @param content
     * @param private_key
     * @param input_charset
     * @return
     * @throws Exception
     */
    public static String decrypt(String content, String private_key, String input_charset) throws Exception {
        PrivateKey prikey = getPrivateKey(private_key);

        Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
        cipher.init(Cipher.DECRYPT_MODE, prikey);

        InputStream ins = new ByteArrayInputStream(Base64Util.decode(content));
        ByteArrayOutputStream writer = new ByteArrayOutputStream();
        byte[] buf = new byte[128];
        int bufl;

        while ((bufl = ins.read(buf)) != -1) {
            byte[] block = null;

            if (buf.length == bufl) {
                block = buf;
            } else {
                block = new byte[bufl];
                for (int i = 0; i < bufl; i++) {
                    block[i] = buf[i];
                }
            }

            writer.write(cipher.doFinal(block));
        }

        return new String(writer.toByteArray(), input_charset);
    }

    /**
     * 获得私钥
     *
     * @param key
     *            私钥
     * @throws Exception
     */
    public static PrivateKey getPrivateKey(String key) throws Exception {

        byte[] keyBytes;

        keyBytes = Base64Util.decode(key);

        PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(keyBytes);

        KeyFactory keyFactory = KeyFactory.getInstance("RSA");

        PrivateKey privateKey = keyFactory.generatePrivate(keySpec);

        return privateKey;
    }

    /**
     * 得到公钥
     *
     * @param bysKey
     * @return
     */
    private static PublicKey getPublicKeyFromX509(String bysKey) throws NoSuchAlgorithmException, Exception {
        byte[] decodedKey = Base64Util.decode(bysKey);
        X509EncodedKeySpec x509 = new X509EncodedKeySpec(decodedKey);

        KeyFactory keyFactory = KeyFactory.getInstance("RSA");
        return keyFactory.generatePublic(x509);
    }

    /**
     * 使用公钥加密
     *
     * @param content 密文
     * @param pub_key 公钥
     * @return
     */
    public static String encryptByPublic(String content, String pub_key) {
        try {
            PublicKey pubkey = getPublicKeyFromX509(pub_key);

            Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
            cipher.init(Cipher.ENCRYPT_MODE, pubkey);

            byte plaintext[] = content.getBytes("UTF-8");
            byte[] output = cipher.doFinal(plaintext);

            String s = new String(Base64Util.encode(output));

            return s;

        } catch (Exception e) {
            return null;
        }
    }
}

public final class Base64Util {

    static private final int     BASELENGTH           = 128;
    static private final int     LOOKUPLENGTH         = 64;
    static private final int     TWENTYFOURBITGROUP   = 24;
    static private final int     EIGHTBIT             = 8;
    static private final int     SIXTEENBIT           = 16;
    static private final int     FOURBYTE             = 4;
    static private final int     SIGN                 = -128;
    static private final char    PAD                  = '=';
    static private final boolean fDebug               = false;
    static final private byte[]  base64Alphabet       = new byte[BASELENGTH];
    static final private char[]  lookUpBase64Alphabet = new char[LOOKUPLENGTH];

    static {
        for (int i = 0; i < BASELENGTH; ++i) {
            base64Alphabet[i] = -1;
        }
        for (int i = 'Z'; i >= 'A'; i--) {
            base64Alphabet[i] = (byte) (i - 'A');
        }
        for (int i = 'z'; i >= 'a'; i--) {
            base64Alphabet[i] = (byte) (i - 'a' + 26);
        }

        for (int i = '9'; i >= '0'; i--) {
            base64Alphabet[i] = (byte) (i - '0' + 52);
        }

        base64Alphabet['+'] = 62;
        base64Alphabet['/'] = 63;

        for (int i = 0; i <= 25; i++) {
            lookUpBase64Alphabet[i] = (char) ('A' + i);
        }

        for (int i = 26, j = 0; i <= 51; i++, j++) {
            lookUpBase64Alphabet[i] = (char) ('a' + j);
        }

        for (int i = 52, j = 0; i <= 61; i++, j++) {
            lookUpBase64Alphabet[i] = (char) ('0' + j);
        }
        lookUpBase64Alphabet[62] = (char) '+';
        lookUpBase64Alphabet[63] = (char) '/';

    }

    private static boolean isWhiteSpace(char octect) {
        return (octect == 0x20 || octect == 0xd || octect == 0xa || octect == 0x9);
    }

    private static boolean isPad(char octect) {
        return (octect == PAD);
    }

    private static boolean isData(char octect) {
        return (octect < BASELENGTH && base64Alphabet[octect] != -1);
    }

    /**
     * Encodes hex octects into Base64
     *
     * @param binaryData Array containing binaryData
     * @return Encoded Base64 array
     */
    public static String encode(byte[] binaryData) {

        if (binaryData == null) {
            return null;
        }

        int lengthDataBits = binaryData.length * EIGHTBIT;
        if (lengthDataBits == 0) {
            return "";
        }

        int fewerThan24bits = lengthDataBits % TWENTYFOURBITGROUP;
        int numberTriplets = lengthDataBits / TWENTYFOURBITGROUP;
        int numberQuartet = fewerThan24bits != 0 ? numberTriplets + 1 : numberTriplets;
        char encodedData[] = null;

        encodedData = new char[numberQuartet * 4];

        byte k = 0, l = 0, b1 = 0, b2 = 0, b3 = 0;

        int encodedIndex = 0;
        int dataIndex = 0;
        if (fDebug) {
            System.out.println("number of triplets = " + numberTriplets);
        }

        for (int i = 0; i < numberTriplets; i++) {
            b1 = binaryData[dataIndex++];
            b2 = binaryData[dataIndex++];
            b3 = binaryData[dataIndex++];

            if (fDebug) {
                System.out.println("b1= " + b1 + ", b2= " + b2 + ", b3= " + b3);
            }

            l = (byte) (b2 & 0x0f);
            k = (byte) (b1 & 0x03);

            byte val1 = ((b1 & SIGN) == 0) ? (byte) (b1 >> 2) : (byte) ((b1) >> 2 ^ 0xc0);
            byte val2 = ((b2 & SIGN) == 0) ? (byte) (b2 >> 4) : (byte) ((b2) >> 4 ^ 0xf0);
            byte val3 = ((b3 & SIGN) == 0) ? (byte) (b3 >> 6) : (byte) ((b3) >> 6 ^ 0xfc);

            if (fDebug) {
                System.out.println("val2 = " + val2);
                System.out.println("k4   = " + (k << 4));
                System.out.println("vak  = " + (val2 | (k << 4)));
            }

            encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];
            encodedData[encodedIndex++] = lookUpBase64Alphabet[val2 | (k << 4)];
            encodedData[encodedIndex++] = lookUpBase64Alphabet[(l << 2) | val3];
            encodedData[encodedIndex++] = lookUpBase64Alphabet[b3 & 0x3f];
        }

        // form integral number of 6-bit groups
        if (fewerThan24bits == EIGHTBIT) {
            b1 = binaryData[dataIndex];
            k = (byte) (b1 & 0x03);
            if (fDebug) {
                System.out.println("b1=" + b1);
                System.out.println("b1<<2 = " + (b1 >> 2));
            }
            byte val1 = ((b1 & SIGN) == 0) ? (byte) (b1 >> 2) : (byte) ((b1) >> 2 ^ 0xc0);
            encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];
            encodedData[encodedIndex++] = lookUpBase64Alphabet[k << 4];
            encodedData[encodedIndex++] = PAD;
            encodedData[encodedIndex++] = PAD;
        } else if (fewerThan24bits == SIXTEENBIT) {
            b1 = binaryData[dataIndex];
            b2 = binaryData[dataIndex + 1];
            l = (byte) (b2 & 0x0f);
            k = (byte) (b1 & 0x03);

            byte val1 = ((b1 & SIGN) == 0) ? (byte) (b1 >> 2) : (byte) ((b1) >> 2 ^ 0xc0);
            byte val2 = ((b2 & SIGN) == 0) ? (byte) (b2 >> 4) : (byte) ((b2) >> 4 ^ 0xf0);

            encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];
            encodedData[encodedIndex++] = lookUpBase64Alphabet[val2 | (k << 4)];
            encodedData[encodedIndex++] = lookUpBase64Alphabet[l << 2];
            encodedData[encodedIndex++] = PAD;
        }

        return new String(encodedData);
    }

    /**
     * Decodes Base64 data into octects
     *
     * @param encoded string containing Base64 data
     * @return Array containind decoded data.
     */
    public static byte[] decode(String encoded) {

        if (encoded == null) {
            return null;
        }

        char[] base64Data = encoded.toCharArray();
        // remove white spaces
        int len = removeWhiteSpace(base64Data);

        if (len % FOURBYTE != 0) {
            return null;//should be divisible by four
        }

        int numberQuadruple = (len / FOURBYTE);

        if (numberQuadruple == 0) {
            return new byte[0];
        }

        byte decodedData[] = null;
        byte b1 = 0, b2 = 0, b3 = 0, b4 = 0;
        char d1 = 0, d2 = 0, d3 = 0, d4 = 0;

        int i = 0;
        int encodedIndex = 0;
        int dataIndex = 0;
        decodedData = new byte[(numberQuadruple) * 3];

        for (; i < numberQuadruple - 1; i++) {

            if (!isData((d1 = base64Data[dataIndex++])) || !isData((d2 = base64Data[dataIndex++]))
                || !isData((d3 = base64Data[dataIndex++]))
                || !isData((d4 = base64Data[dataIndex++]))) {
                return null;
            }//if found "no data" just return null

            b1 = base64Alphabet[d1];
            b2 = base64Alphabet[d2];
            b3 = base64Alphabet[d3];
            b4 = base64Alphabet[d4];

            decodedData[encodedIndex++] = (byte) (b1 << 2 | b2 >> 4);
            decodedData[encodedIndex++] = (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
            decodedData[encodedIndex++] = (byte) (b3 << 6 | b4);
        }

        if (!isData((d1 = base64Data[dataIndex++])) || !isData((d2 = base64Data[dataIndex++]))) {
            return null;//if found "no data" just return null
        }

        b1 = base64Alphabet[d1];
        b2 = base64Alphabet[d2];

        d3 = base64Data[dataIndex++];
        d4 = base64Data[dataIndex++];
        if (!isData((d3)) || !isData((d4))) {//Check if they are PAD characters
            if (isPad(d3) && isPad(d4)) {
                if ((b2 & 0xf) != 0)//last 4 bits should be zero
                {
                    return null;
                }
                byte[] tmp = new byte[i * 3 + 1];
                System.arraycopy(decodedData, 0, tmp, 0, i * 3);
                tmp[encodedIndex] = (byte) (b1 << 2 | b2 >> 4);
                return tmp;
            } else if (!isPad(d3) && isPad(d4)) {
                b3 = base64Alphabet[d3];
                if ((b3 & 0x3) != 0)//last 2 bits should be zero
                {
                    return null;
                }
                byte[] tmp = new byte[i * 3 + 2];
                System.arraycopy(decodedData, 0, tmp, 0, i * 3);
                tmp[encodedIndex++] = (byte) (b1 << 2 | b2 >> 4);
                tmp[encodedIndex] = (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
                return tmp;
            } else {
                return null;
            }
        } else { //No PAD e.g 3cQl
            b3 = base64Alphabet[d3];
            b4 = base64Alphabet[d4];
            decodedData[encodedIndex++] = (byte) (b1 << 2 | b2 >> 4);
            decodedData[encodedIndex++] = (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
            decodedData[encodedIndex++] = (byte) (b3 << 6 | b4);

        }

        return decodedData;
    }

    /**
     * remove WhiteSpace from MIME containing encoded Base64 data.
     *
     * @param data  the byte array of base64 data (with WS)
     * @return      the new length
     */
    private static int removeWhiteSpace(char[] data) {
        if (data == null) {
            return 0;
        }

        // count characters that's not whitespace
        int newSize = 0;
        int len = data.length;
        for (int i = 0; i < len; i++) {
            if (!isWhiteSpace(data[i])) {
                data[newSize++] = data[i];
            }
        }
        return newSize;
    }
}

 

说明

前端生成加密的字符串encrypted，传到后台，java使用私钥进行解密即可。