[Go] RSA 私钥加密公钥解密，及和 Java 实现互通

golang RSA 私钥加密公钥解密，及和 Java 实现互通。

在golang中使用RSA算法时，一般都是公钥加密，私钥解密，这是一个常见的场景。但是在实际使用中，

往往需要和其他项目进行交互，其他项目实现就不一定是按标准使用的，比如Java、PHP中就比较常见，

经常有项目用私钥加密，公钥解密，实现参考Java使用RSA加密解密及签名校验，甚至直接就拿来就用，

这个时候就需要了解在golang中如何实现公钥加密，私钥解密。

下面是golang的公钥加密，私钥解密示例，实现和java的互通。

RSA 加密与解密

RSA 加密算法是一种非对称加密算法，在许多项目中广泛使用，是当前数据安全加密中最常用的算法之一。在 Go 语言中，RSA 的加密、解密、签名与验签主要通过 crypto/x509 和 crypto/rsa 两个包的方法来实现。

RSA 通过生成一对公钥和私钥来进行加密和解密，公钥与私钥是相互对应的。公钥可以用来加密数据，但不能用于解密；而私钥则可以解密由对应公钥加密的数据。公钥可以公开分发，而私钥需要妥善保管，只有拥有私钥的人才能解密通过公钥加密的信息。

正常使用时，一般使用公钥加密，私钥解密。但是某些场景下，需要使用私钥加密，公钥解密，比较常见的就是签名验证。

Java RSA 加密解密示例

参考Java使用RSA加密解密及签名校验

实现测试示例如下，RSA密钥生成都为2048位：

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import java.io.*;
//import java.io.ByteArrayOutputStream;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.Key;
import java.security.KeyFactory;
import java.security.PrivateKey;
import java.security.PublicKey;
import javax.crypto.Cipher;
import java.security.spec.X509EncodedKeySpec;
import java.util.Base64;
import java.util.Arrays;

public class HelloWorld
{

        static String privateKey = "-----BEGIN PRIVATE KEY-----\n"
                + "MIIEvAIBADANBgkqhkiG9w0BAQEFAASCBKYwggSiAgEAAoIBAQCucd9Bhz9lBGBU\n"
                + "Q2BPyufbSszdjfSxgPrB4/ua9tYkMhsM6NtWKVXhB8Mo9wEoTNNShAvcS/Xk/dxn\n"
                + "j+f3aMX1QHUys/Cf7AFfdz9B6LHRyaJrJEUiuZhpH3cohT/cZPWCfXMC8TkmM/WF\n"
                + "sJsUIg53J9j/KzamEYrREcZylxdh77Q6zpsloXmj0sVqvzy5L8HJYfttH/XNELzu\n"
                + "9ZEnBCi23Vo2Dt2Q6ZZO/MGJp1J2OAcaBBZ+B0i1E1c/MA2VNwuXx+v1Nc3SUyNy\n"
                + "bqM0zfNWoegTqssfAxOTsFclAiMIL96J9GJsqfl9IQzClgV7/anhwfTA3qEjpYLC\n"
                + "qxIyM0wVAgMBAAECggEACufBfjY3R1hjsUDZB4P2xKXDcuJJ9sLKak6XTxO5RWAA\n"
                + "gukXtSY2YS/8ClaOsvdCirkIiMgS4jLgkXTUmonpPjC+YuIO2+CEIXSx9qvWWfgR\n"
                + "+EK3M7mIhqHZ8CWMXXnOQ08WXou39+Rtp+LnfvW2E8rg7OrFqtIT7IgA8O7zHkMk\n"
                + "dBNUq5GO/nQ4GUmEbCb10Bs8Fb1Ibf4vUhAmgvpuS7oFfEcecoJmvU2x/UVTdWsL\n"
                + "1A+kzxvq0fShhmeMct1RJD1q33Ifv5C6Z3CgjHWJAjUaWR0+qTS61aS0u5Uh7FSl\n"
                + "zewiiDYueDhD6bQB22cCSzIi5yDDY9XtQl+bCncsjQKBgQDib39w0swSpNn6LzYz\n"
                + "Pm8LtTAo4ARFpHdZjR3+pOCtKHnBY89JHNxk1vTveY8lvMecqELSSLUhSYWgHVpw\n"
                + "3bWB1NXS7+ACIrSD0x93Qv9mJ9ZCUW8r4HcZ9Eo+z52Anoe6VOqg83uIgPGCLcvJ\n"
                + "nxXFOlwW1MGJUEHDnv5PsUHfJwKBgQDFOJvJmn1DgP1CHAEmnjhfKI/JnhS941Pi\n"
                + "terIHLq9t7vv6ASMin42bHGWxFfdEoLFWlssqr8xvPFpNiMqOA1A7pZs8kcJgLnu\n"
                + "Z7Il8M1Fx2BTk+UIQMWVX7Ftm3Jpdc4/qjNnmUEE7ITDIcKzXuHp48s2AmELSpc6\n"
                + "Zyq0ALYAYwKBgBOTlC8K6n3KJtZMcqEniq42cf12sKfcujzRyIAVfR87Wptvp6Io\n"
                + "jp1hQDfcCJY4pgFTQsOvaYmBM75OC12qrWCWKA5ekr1chsLG4/eJoU8RrqJ5K+Vd\n"
                + "OK7Twf+AL5vJGO7xHH/hzRJWI4sfrni1+knc681Fg539hFIHUvFM3+cNAoGAQmBY\n"
                + "BlUpfZOnKR3VwVKU9GnpYtkCcBpXfEDvwOPycbGp3gd/qHFgIx8CZ9SzIaN+Qb+0\n"
                + "WecprCrEMT3YPfhZdZYXKJmuEOOzMCrUSXKvE6ITqG1pMwrhtPFc/N/JdPcCMGkv\n"
                + "Hdn1iRu1Xxs4tTfk3twc45OPZ8Z1+WEJfUWT+7MCgYAYfHXHVF5U9XLsvCQz4z37\n"
                + "FkIVtrYjQ6D2329+YTO+axlfRB8v0EHsPIeMQcWFxIOybNWFu5kFJmWB8T1ycqk/\n"
                + "p9i04GoW44woZfzP8FWFw5B8wTXn9yqq3RVm2f5bsUGHv/32cPuGmi1aG2kNGJb0\n"
                + "LoLK4I5s6vHfBZ+wahqiTQ==\n"
                + "-----END PRIVATE KEY-----";

        static String publicKey = "MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEArnHfQYc/ZQRgVENgT8rn\n"
            + "20rM3Y30sYD6weP7mvbWJDIbDOjbVilV4QfDKPcBKEzTUoQL3Ev15P3cZ4/n92jF\n"
            + "9UB1MrPwn+wBX3c/Qeix0cmiayRFIrmYaR93KIU/3GT1gn1zAvE5JjP1hbCbFCIO\n"
            + "dyfY/ys2phGK0RHGcpcXYe+0Os6bJaF5o9LFar88uS/ByWH7bR/1zRC87vWRJwQo\n"
            + "tt1aNg7dkOmWTvzBiadSdjgHGgQWfgdItRNXPzANlTcLl8fr9TXN0lMjcm6jNM3z\n"
            + "VqHoE6rLHwMTk7BXJQIjCC/eifRibKn5fSEMwpYFe/2p4cH0wN6hI6WCwqsSMjNM\n"
            + "FQIDAQAB";


       /**
        * RSA加密解密测试示例
        * @throws Exception
        */
       public static void main(String[] args)  throws Exception 
       {
                 System.out.println("Hello World!");

                 // Read in the key into a String        
                 StringBuilder pkcs8Lines = new StringBuilder();
                 BufferedReader rdr = new BufferedReader(new StringReader(privateKey));
                 String line;
                 while ((line = rdr.readLine()) != null) {
                     pkcs8Lines.append(line);
                 }

                 // Remove the "BEGIN" and "END" lines, as well as any whitespace
                 String pkcs8Pem = pkcs8Lines.toString();
                 pkcs8Pem = pkcs8Pem.replace("-----BEGIN PRIVATE KEY-----", "");
                 pkcs8Pem = pkcs8Pem.replace("-----END PRIVATE KEY-----", "");
                 pkcs8Pem = pkcs8Pem.replaceAll("\\s+","");
                 System.out.println("pkcs8Pem:" + pkcs8Pem);

                 // Base64 decode the result
                 // byte[] pkcs8EncodedBytes = Base64.decode(pkcs8Pem, Base64.DEFAULT);
                 byte [] pkcs8EncodedBytes = decode(pkcs8Pem);
                 System.out.println("pkcs8EncodedBytes byte:" + Arrays.toString(pkcs8EncodedBytes));
                 System.out.println("pkcs8Pem byte:" + Arrays.toString(pkcs8Pem.getBytes()));

                 // extract the private key
                 PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(pkcs8EncodedBytes);
                 KeyFactory kf = KeyFactory.getInstance("RSA");
                 PrivateKey privKey = kf.generatePrivate(keySpec);
                 System.out.println(privKey);

                 String param = "{\"name\":\"aa\"}";
                 String p1 = encode(param.getBytes());
                 System.out.println("p1:" + p1);

                 byte[] p2 = decode(p1);
                 System.out.println("p2:" + Arrays.toString(p2));

                 String encryptData = encryptForPrivateKey(param, pkcs8Pem);
                 System.out.println("加密后内容:" + encryptData);

                 String publicKey2 = "MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAv651nntK13ezxNPnQ5s7\n"
                     + "8nwRK45rg28tvhMr9rt6HNrS1bhKEtysx+p4jKuA1BHBHWWSA5SlRlruS1zZIpgy\n"
                     + "p5u8uqhAALp3yBa0Yw/XcyBe2zuY5mfCCL3ftKw3o9rzFsG6obnwLXnGQyKMPmxP\n"
                     + "/pIeZHkIUMo/EjI5ExKG+dMQn1Fp6wo/+zbnZIk1ewQH4E0+iPyWa2nn2RBPFiYS\n"
                     + "QPPvsypfkE46z0VG7eqAxqrUSzm26qhYgv+lqIn/Zqq/ZnTJO+2SDI8GsbEaqXiF\n"
                     + "QRrWZrDcU92s76rwlIHUBlEqRKNXc+BcfWwEx4giEk87GPC9QHxjLgwzEeNXjih2\n"
                     + "jwIDAQAB";

                 // String encryptData2 = "bl7TWxqWq17amPInw5gLEcNds5G3v2Gm8MNeRBniliTiPyUjMCZwbtiJK9/M423OOqYU3e+Kk3wROyk2K/5WSmgkfdaLWBgpRKWDO/x8H9Sg/5QsBnMCrosM/MFK9ayyJiuE5nM6PU3qCGZ+/v0nR0RagUo9Eqxx6g8ZQWMXBtCEd1yyGpnRzxmvbX77HYYs26gKKDduvbwhxjwEDBzByxZrhLQ03wBSJATRNevGEimlMK4ev+JVk0lqCz4Y0M28eskrvcT2246+OB4M/tElt4gGD/MTtFUAjJ/pKnyX/dRL/iIQzU6afxr3+QDBK7VHyNr3LrPJNXUeYNYwyJWrpw==";
                 String encryptData2 = "Wzfl/uB/7cXPkRjLJ/guruu9NytzdT+9dM3dsMAOYHLdBEcEPBsDkNICEmTlM7ubkGmNE6rxeZ/20SpaSWEY89zahoAb7GMu1ceGPbJZrb5F26BfMHsA+CK5Y6MLtbl/ssaq/r9U0xB/DJeDJrOUs8hO8YPgGxeOtzMuJhHT4BVh4Td1SBA9hSJOWkMZCkwGP6RaSl4eunggk1Kmuu5rxEOIv9B7TWCIRpuy2AwtLwRCIbZjIilVVFMTzpuUySKWlcl5qD/OdYKfidDtXvIam2J9JoH3TddUKSsbcPDsb0AC8BR8a9CRC72jGCvftxqUIwWMWTZgqViEWeEcSTK/gw==";
                 
                 String decryptData = decryptForPublicKey(encryptData2, publicKey2);
                 System.out.println("解密后内容:" + decryptData);

                 String rSignData = "NZQrkpicy7wGx1fWu+8KhU5fWfI3oTAa6Deg0/GEDVcOwpwpoybLRdI4NCM7I8mLSNh/KI+d62gqcWnT399XQCGiesZlSR7ux7TM/aQe+RqLIvPNWcfcxyEGmDZxDgvnjTP5qzJYaQKC9DK4w2SelwDab7nhvV30uV24kQeBJGjGrsT2xZVPnWcsc8UaV+QUpajmV70QdYilDVn9RYht891Uwqm5twqcYej3ba9ZBE16cmaNGeveegXvwkGK6akmXR9covoLMqDUvq0HE1Mr2S43nMisF/vw2uQxgRq+Dr44OBbPMY9qICnd99B7csv498CfZLMRf/4+92TPUClnbw==";
                 // RSA验签
                 boolean result = doCheck(decryptData, rSignData, publicKey2, "UTF-8");
                 System.out.print("验签结果:" + result);
       }

       /**
        * RSA验签名检查
        * @param content 待签名数据
        * @param sign 签名值
        * @param publicKey 分配给开发商公钥
        * @param encode 字符集编码
        * @return 布尔值
        */
       public static boolean doCheck(String content, String sign, String publicKey,String encode)
       {
           try
           {
               KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
               byte[] encodedKey = decode(publicKey);
               PublicKey pubKey = keyFactory.generatePublic(new X509EncodedKeySpec(encodedKey));
               java.security.Signature signature = java.security.Signature
                   .getInstance(SIGN_ALGORITHMS);
               signature.initVerify(pubKey);
               signature.update( content.getBytes(encode) );

               boolean bverify = signature.verify( decode(sign) );
               System.out.print("验签结果-----:" + bverify);
               return bverify;

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

           return false;
       }

       /**
        * 签名算法
        */
       public static final String SIGN_ALGORITHMS = "SHA256WithRSA";

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

       /**
        * RSA最大加密明文大小
        */
       private static final int MAX_ENCRYPT_BLOCK = 245;

       /**
        * RSA最大解密密文大小
        */
       private static final int MAX_DECRYPT_BLOCK = 256;

       /**
        * 私钥加密
        * @param privateKeyStr 私钥
        * @param data 加密字符串
        * @return String 密文数据
        * @throws Exception
        */
       public static String encryptForPrivateKey(String data, String privateKeyStr) throws Exception{
           byte[] decryptedData = encryptByPrivateKey(data.getBytes(), privateKeyStr);
           // return Base64.encode(decryptedData);
           // return Base64.getEncoder().encodeToString(decryptedData);
           return encode(decryptedData);
       }

       /**
        * <p>
        * 私钥加密
        * </p>
        * 
        * @param data
        *            源数�?
        * @param privateKey
        *            私钥(BASE64编码)
        * @return
        * @throws Exception
        */
       public static byte[] encryptByPrivateKey(byte[] data, String privateKey) throws Exception {
           System.out.println("privateKey:" + privateKey);
           // byte[] keyBytes = Base64.decode(privateKey);
           // byte[] keyBytes = Base64.getDecoder().decode(privateKey);
           // byte[] keyBytes = privateKey.getBytes();
           // System.out.println("privateKey byte:" + Arrays.toString(keyBytes));
           byte [] pkcs8EncodedBytes = decode(privateKey);
           PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(pkcs8EncodedBytes);

           // KeyFactory kf = KeyFactory.getInstance("RSA");
           // PrivateKey privKey = kf.generatePrivate(keySpec);
           // System.out.println(privKey);

           KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
           Key privateK = keyFactory.generatePrivate(pkcs8KeySpec);
           System.out.println("---" + privateK);
           Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
           cipher.init(Cipher.ENCRYPT_MODE, privateK);
           int inputLen = data.length;
           System.out.println("en inputLen:" + inputLen + "---" + MAX_ENCRYPT_BLOCK);
           ByteArrayOutputStream out = new ByteArrayOutputStream();
           int offSet = 0;
           byte[] cache;
           int i = 0;
           // 对数据分段加密
           while (inputLen - offSet > 0) {
               System.out.println("----:" + inputLen + "===" + offSet + " i " + i);
               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;
       }

       /**
        * 公钥解密方法
        * @param publicKey
        * @param plainTextData 密文
        * @return 明文
        * @throws Exception
        */
       public static String decryptForPublicKey(String plainTextData, String publicKey) throws Exception{
           byte[] decryptedData = decryptByPublicKey(decode(plainTextData), publicKey);
           return new String(decryptedData);
       }

       /**
        * <p>
        * 公钥解密
        * </p>
        * 
        * @param encryptedData
        *            已加密数据
        * @param publicKey
        *            公钥(BASE64编码)
        * @return
        * @throws Exception
        */
       public static byte[] decryptByPublicKey(byte[] encryptedData, String publicKey) throws Exception {
           byte[] keyBytes = decode(publicKey);
           System.out.println("kkk----:" + keyBytes.length);
           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;
           System.out.println("inputLen:" + inputLen);
           ByteArrayOutputStream out = new ByteArrayOutputStream();
           int offSet = 0;
           byte[] cache;
           int i = 0;
           // 对数据分段解密
           while (inputLen - offSet > 0) {
               System.out.println("de ----:" + inputLen + "===" + offSet + " i " + i);
               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;
       }



// 标准 base64

    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;
    }
}

运行查看结果

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javac HelloWorld.java
java HelloWorld

golang 实现私钥加密、公钥解密

参考Golang RSA 如何私钥加密公钥解密

RSA密钥生成都为2048位。

公钥解密实现

对于 2048 位 (256 字节) 的 RSA 密钥，最大能加密的数据长度约为 245 字节 (因为 PKCS#1 v1.5 填充需要 11 字节)。

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// EncryptForPrivateKey 加密长消息，RSA最大加密明文大小256-11=245字节，这里对245字节进行分组加密
func EncryptForPrivateKey(data []byte, privKey []byte) (string, error) {
	block, _ := pem.Decode(privKey)
	if block == nil {
		return "", errors.New("private key error")
	}
	priv, err := x509.ParsePKCS8PrivateKey(block.Bytes)
	if err != nil {
		return "", err
	}

	rsaPrivateKey, ok := priv.(*rsa.PrivateKey)
	if !ok {
		return "", errors.New("key is not an RSA private key")
	}
	publicKey := &rsaPrivateKey.PublicKey

	// RSA encryption with PKCS1v15 padding
	// The chunk size must be smaller than the key size - 11 bytes (for padding)
	maxEncryptBlock := publicKey.Size() - 11

	dataLen := len(data)
	var encryptedBytes bytes.Buffer

	for i := 0; i < dataLen; i += maxEncryptBlock {
		end := min(i+maxEncryptBlock, dataLen)

		chunk := data[i:end]
		encryptedChunk, err := rsa.SignPKCS1v15(nil, rsaPrivateKey, crypto.Hash(0), chunk[:])
		if err != nil {
			return "", fmt.Errorf("encrypt chunk error: %v", err)
		}

		encryptedBytes.Write(encryptedChunk)
	}

	return base64.StdEncoding.EncodeToString(encryptedBytes.Bytes()), nil
}

Go 的签名是采用的 PKCS #1 v1.5 padding 方式。

私钥签名常见是用在签名验证中，在签名验证中，是不需要解出明文，只需要验证签名是否正确，所以是有传入hash参数的，

如果想解出明文，只需要在加密时不传入hash参数即可，传crypto.Hash(0)则表示不进行任务hash处理。

1

encryptedChunk, err := rsa.SignPKCS1v15(nil, rsaPrivateKey, crypto.Hash(0), chunk[:])

RSA签名、验签实现

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// 签名算法，对应java RSA.sign SHA256WithRSA
func RsaSign(origData []byte, privKey []byte) (string, error) {
	block, _ := pem.Decode(privKey)
	if block == nil {
		return "", errors.New("private key error")
	}
	priv, err := x509.ParsePKCS8PrivateKey(block.Bytes)
	if err != nil {
		return "", err
	}

	hashed := sha256.Sum256(origData) // 使用SHA-256哈希数据
	signature, err := rsa.SignPKCS1v15(rand.Reader, priv.(*rsa.PrivateKey), crypto.SHA256, hashed[:])
	if err != nil {
		return "", err
	}

	return base64.StdEncoding.EncodeToString(signature), err
}

// RsaVerifySignature 验证签名
func RsaVerifySignature(origData []byte, signData string, pubKey []byte) error {
	signDataBytes, err := base64.StdEncoding.DecodeString(signData)
	if err != nil {
		return err
	}

	block, _ := pem.Decode(pubKey)
	if block == nil {
		return errors.New("private key error")
	}

	pub, err := x509.ParsePKIXPublicKey(block.Bytes)
	if err != nil {
		return fmt.Errorf("parse public key error: %v", err)
	}

	publicKey, ok := pub.(*rsa.PublicKey)
	if !ok {
		return errors.New("key is not an RSA private key")
	}

	hashed := sha256.Sum256(origData) // 使用SHA-256哈希数据
	err = rsa.VerifyPKCS1v15(publicKey, crypto.SHA256, hashed[:], signDataBytes[:])
	return err
}

公钥解密实现：

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// DecryptForPublicKey 解密分块加密的长消息
func DecryptForPublicKey(encryptedData string, pubKey []byte) ([]byte, error) {
	encryptedDataBytes, err := base64.StdEncoding.DecodeString(encryptedData)
	if err != nil {
		return nil, fmt.Errorf("base64 decode error: %v", err)
	}

	block, _ := pem.Decode(pubKey)
	if block == nil {
		return nil, errors.New("private key error")
	}

	pub, err := x509.ParsePKIXPublicKey(block.Bytes)
	if err != nil {
		return nil, fmt.Errorf("parse public key error: %v", err)
	}

	publicKey, ok := pub.(*rsa.PublicKey)
	if !ok {
		return nil, errors.New("key is not an RSA private key")
	}

	maxDecryptBlock := publicKey.Size()

	dataLen := len(encryptedDataBytes)
	var decryptedBytes bytes.Buffer

	for i := 0; i < dataLen; i += maxDecryptBlock {
		end := min(i+maxDecryptBlock, dataLen)

		chunk := encryptedDataBytes[i:end]
		decryptedChunk, err := publicKeyDecrypt(chunk[:], publicKey)
		if err != nil {
			return nil, fmt.Errorf("decrypt chunk error: %v", err)
		}

		decryptedBytes.Write(decryptedChunk[:])
	}

	return decryptedBytes.Bytes(), nil
}

func publicKeyDecrypt(encryptedData []byte, pubKey *rsa.PublicKey) ([]byte, error) {
	c := new(big.Int).SetBytes(encryptedData)
	if c.Cmp(pubKey.N) > 0 {
		return nil, errors.New("加密数据太大")
	}

	m := new(big.Int).Exp(c, big.NewInt(int64(pubKey.E)), pubKey.N)

	modulusSize := (pubKey.N.BitLen() + 7) / 8
	plaintext := make([]byte, modulusSize)
	mBytes := m.Bytes()
	copy(plaintext[modulusSize-len(mBytes):], mBytes)

	// 检查并移除PKCS#1 v1.5填充
	if len(plaintext) < 11 {
		return nil, errors.New("解密错误：数据太短")
	}

	fmt.Println("plaintext:", plaintext)
	// PKCS#1 v1.5填充格式: 0x00 0x02 [随机非零字节] 0x00 [原始数据]
	if plaintext[0] != 0x00 || plaintext[1] != 0x02 {
		return nil, errors.New("解密错误：无效的填充格式")
	}

	// 查找分隔符0x00
	separator := bytes.IndexByte(plaintext[2:], 0x00)
	if separator == -1 {
		return nil, errors.New("解密错误：找不到填充分隔符")
	}

	// 返回原始数据部分
	return plaintext[3+separator:], nil
}

这里在publicKeyDecrypt函数中，首先检查填充格式，然后查找填充的分隔符，并返回原始数据部分。

为什么要这样做吗？

在网上比较多的实现私钥加密、公钥解密都是这样：

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// 真正的私钥加密（非标准）
func RealPrivateEncrypt(msg []byte, privKey *rsa.PrivateKey) ([]byte, error) {
    // 直接使用RSA核心运算
    c := new(big.Int).SetBytes(msg)
    if c.Cmp(privKey.N) > 0 {
        return nil, errors.New("消息太长")
    }
    m := new(big.Int).Exp(c, privKey.D, privKey.N)
    return m.Bytes(), nil
}

// 对应的公钥解密
func RealPublicDecrypt(ciphertext []byte, pubKey *rsa.PublicKey) ([]byte, error) {
    c := new(big.Int).SetBytes(ciphertext)
    m := new(big.Int).Exp(c, big.NewInt(int64(pubKey.E)), pubKey.N)
    return m.Bytes(), nil
}

但是这样使用原始RSA运算进行"公钥解密"时，直接使用 big.Int 的 Bytes() 方法会导致数据长度固定为密钥长度（256字节），

并且高位填充255（即0xFF），所以就需要像publicKeyDecrypt一样去掉高位填充，才能等到真实的明文内容。

还有个问题就是，这里为什么填充的是0x00 0x02?

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	// PKCS#1 v1.5填充格式: 0x00 0x02 [随机非零字节] 0x00 [原始数据]
	if plaintext[0] != 0x00 || plaintext[1] != 0x02 {
		return nil, errors.New("解密错误：无效的填充格式")
	}

这其实是PKCS#1 填充类型的区别，要看是加密填充还是签名填充：

加密填充 (RSAES-PKCS1-v1_5) 格式：0x00 0x02
签名填充 (RSASSA-PKCS1-v1_5) 填充格式：0x00 0x01

而上面java代码中，使用的是加密填充，所以填充格式是0x00 0x01

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// Java 代码使用的是加密填充
Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
cipher.init(Cipher.ENCRYPT_MODE, privateK);  // 这会使用 PKCS#1 加密填充

java中填充的格式是：

如果使用 Cipher.ENCRYPT_MODE → 加密填充 (0x02)
如果使用 Signature.getInstance("SHA256withRSA") → 签名填充 (0x01)

数据特征：

加密填充：第二个字节是 0x02，后面是随机非零字节
签名填充：第二个字节是 0x01，后面是连续的 0xFF

所以如果要和java互通，就要保持填充的格式一致，在项目中视具体情况修改填充格式。

Contents