java RSA验签方法

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.security.*;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import javax.crypto.Cipher;
import sun.misc.BASE64Decoder;
import sun.misc.BASE64Encoder;

public class Sha1withRSAUtil {
      /** 指定加密算法为RSA */
      private static String ALGORITHM = "RSA";
      /** 指定key的大小 */
      private static int KEYSIZE = 1024;
      /** 指定公钥存放文件 */
      private static String PUBLIC_KEY_FILE = "d:/PublicKey";
        /** 指定私钥存放文件 */
      private static String PRIVATE_KEY_FILE = "d:/PrivateKey";

private static String PUBLIC_KEY ="你自己的公钥";
public static final String KEY_ALGORITHM = "RSA";

public static final String SIGNATURE_ALGORITHM = "SHA1withRSA";

/**
 * 生成密钥对
 */
public static void generateKeyPair() throws Exception {
    if (getpublickey() == null || getprivatekey() == null) {
        /** RSA算法要求有一个可信任的随机数源 */
        SecureRandom sr = new SecureRandom();
        /** 为RSA算法创建一个KeyPairGenerator对象 */
        KeyPairGenerator kpg = KeyPairGenerator.getInstance(ALGORITHM);
        /** 利用上面的随机数据源初始化这个KeyPairGenerator对象 */
        kpg.initialize(KEYSIZE, sr);
        /** 生成密匙对 */
        KeyPair kp = kpg.generateKeyPair();
        /** 得到公钥 */
        Key publicKey = kp.getPublic();
        /** 得到私钥 */
        Key privateKey = kp.getPrivate();
        /** 用对象流将生成的密钥写入文件 */
        ObjectOutputStream oos1 = new ObjectOutputStream(new FileOutputStream(PUBLIC_KEY_FILE));
        ObjectOutputStream oos2 = new ObjectOutputStream(new FileOutputStream(PRIVATE_KEY_FILE));
        oos1.writeObject(publicKey);
        oos2.writeObject(privateKey);
        /** 清空缓存，关闭文件输出流 */
        oos1.close();
        oos2.close();
    }

}

/**
 * 产生签名
 *
 * @param data
 * @param privateKey
 * @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());
}

/**
 * 验证签名
 *
 * @param signString
 * @param sign
 * @return
 * @throws Exception
 */
public static boolean verify(String signString, String sign) throws Exception {

    byte[] data = decryptBASE64(signString);

    byte[] signs = sign.getBytes();

    try {
        //实例化
        Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
        // 解密由base64编码的公钥
        byte[] keyBytes = decryptBASE64(PUBLIC_KEY);

        // 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);

        // 取公钥对象
        PublicKey pubKey = keyFactory.generatePublic(keySpec);
        //初始化
        signature.initVerify(pubKey);

        //更新
        signature.update(signs);

        //验签
        return signature.verify(data);
    } catch (NoSuchAlgorithmException | InvalidKeyException | SignatureException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

    return false;
}

/**
 * BASE64解密
 *
 * @param key
 * @return
 * @throws Exception
 */
public static byte[] decryptBASE64(String key) throws Exception {
    return (new BASE64Decoder()).decodeBuffer(key);
}

/**
 * BASE64加密
 *
 * @param key
 * @return
 * @throws Exception
 */
public static String encryptBASE64(byte[] key) throws Exception {
    return (new BASE64Encoder()).encodeBuffer(key);
}

/**
 * 加密方法 source： 源数据
 */
public static String encrypt(String source) throws Exception {
    /** 将文件中的公钥对象读出 */
    ObjectInputStream ois = new ObjectInputStream(new FileInputStream(PUBLIC_KEY_FILE));
    Key key = (Key) ois.readObject();
    ois.close();
    /** 得到Cipher对象来实现对源数据的RSA加密 */
    Cipher cipher = Cipher.getInstance(ALGORITHM);
    cipher.init(Cipher.ENCRYPT_MODE, key);
    int MaxBlockSize = KEYSIZE / 8;
    int len = (MaxBlockSize - 11) / 8;
    String[] datas = splitString(source, len);
    StringBuffer mi = new StringBuffer();
    for (String s : datas) {
        mi.append(bcd2Str(cipher.doFinal(s.getBytes())));
    }
    return mi.toString();

}

/**
 * 字符串分片
 *
 * @param string
 *            源字符串
 * @param len
 *            单片的长度（keysize/8）
 * @return
 */
public static String[] splitString(String string, int len) {
    int x = string.length() / len;
    int y = string.length() % len;
    int z = 0;
    if (y != 0) {
        z = 1;
    }
    String[] strings = new String[x + z];
    String str = "";
    for (int i = 0; i < x + z; i++) {
        if (i == x + z - 1 && y != 0) {
            str = string.substring(i * len, i * len + y);
        } else {
            str = string.substring(i * len, i * len + len);
        }
        strings[i] = str;
    }
    return strings;
}

/**
 * bcd 转 Str
 *
 * @param bytes
 * @return
 */
public static String bcd2Str(byte[] bytes) {
    char temp[] = new char[bytes.length * 2], val;
    for (int i = 0; i < bytes.length; i++) {
        val = (char) (((bytes[i] & 0xf0) >> 4) & 0x0f);
        temp[i * 2] = (char) (val > 9 ? val + 'A' - 10 : val + '0');

        val = (char) (bytes[i] & 0x0f);
        temp[i * 2 + 1] = (char) (val > 9 ? val + 'A' - 10 : val + '0');
    }
    return new String(temp);
}

/**
 * 解密
 *
 * @param cryptograph
 *            :密文
 * @return 解密后的明文
 * @throws Exception
 */
public static String decrypt(String cryptograph) throws Exception {
    /** 将文件中的私钥对象读出 */
    @SuppressWarnings("resource")
    ObjectInputStream ois = new ObjectInputStream(new FileInputStream(PRIVATE_KEY_FILE));
    Key key = (Key) ois.readObject();
    /** 得到Cipher对象对已用公钥加密的数据进行RSA解密 */
    Cipher cipher = Cipher.getInstance(ALGORITHM);
    cipher.init(Cipher.DECRYPT_MODE, key);
    int key_len = KEYSIZE / 8;
    byte[] bytes = cryptograph.getBytes();
    byte[] bcd = ASCII2BCD(bytes, bytes.length);
    StringBuffer sBuffer = new StringBuffer();
    byte[][] arrays = splitArray(bcd, key_len);
    for (byte[] arr : arrays) {
        sBuffer.append(new String(cipher.doFinal(arr)));
    }
    return sBuffer.toString();
}

/**
 * ASCII 转 BCD
 *
 * @param ascii
 * @param asc_len
 * @return
 */
public static byte[] ASCII2BCD(byte[] ascii, int asc_len) {
    byte[] bcd = new byte[asc_len / 2];
    int j = 0;
    for (int i = 0; i < (asc_len + 1) / 2; i++) {
        bcd[i] = asc2bcd(ascii[j++]);
        bcd[i] = (byte) (((j >= asc_len) ? 0x00 : asc2bcd(ascii[j++])) + (bcd[i] << 4));
    }
    return bcd;
}

/**
 * asc转bcd
 *
 * @param asc
 * @return
 */
public static byte asc2bcd(byte asc) {
    byte bcd;

    if ((asc >= '0') && (asc <= '9'))
        bcd = (byte) (asc - '0');
    else if ((asc >= 'A') && (asc <= 'F'))
        bcd = (byte) (asc - 'A' + 10);
    else if ((asc >= 'a') && (asc <= 'f'))
        bcd = (byte) (asc - 'a' + 10);
    else
        bcd = (byte) (asc - 48);
    return bcd;
}

/**
 * 字节数组分片
 *
 * @param data
 * @param len
 * @return
 */
public static byte[][] splitArray(byte[] data, int len) {
    int x = data.length / len;
    int y = data.length % len;
    int z = 0;
    if (y != 0) {
        z = 1;
    }
    byte[][] arrays = new byte[x + z][];
    byte[] arr;
    for (int i = 0; i < x + z; i++) {
        arr = new byte[len];
        if (i == x + z - 1 && y != 0) {
            System.arraycopy(data, i * len, arr, 0, y);
        } else {
            System.arraycopy(data, i * len, arr, 0, len);
        }
        arrays[i] = arr;
    }
    return arrays;
}

/** 将文件中的公钥对象读出 */
public static String getpublickey() {

    try {
        @SuppressWarnings("resource")
        ObjectInputStream ois = new ObjectInputStream(new FileInputStream(PUBLIC_KEY_FILE));
        Key key = (Key) ois.readObject();
        String publickey = encryptBASE64(key.getEncoded());
        return publickey;
    } catch (Exception e) {
        e.printStackTrace();
    }
    return null;
}

/** 将文件中的私钥对象读出 */
public static String getprivatekey() {
    try {
        @SuppressWarnings("resource")
        ObjectInputStream ois = new ObjectInputStream(new FileInputStream(PRIVATE_KEY_FILE));
        Key key = (Key) ois.readObject();
        String privatekey = encryptBASE64(key.getEncoded());
        return privatekey;
    } catch (Exception e) {
        e.printStackTrace();
    }
    return null;
}
/** 验签*/
public static void main(String[] args) {
    try {
        String signString = "YBBNqO5nTbuNLAwm4vMkLb/h7CDDTBDuOFgXaui/2UtLl8iwXYdj/LQKvpwpdYTzawfawiidWMzMeFri4753WvlVegk5CKx9CHqo4NbAmI62c+P9yv6rZ398V/Q2NJOeM7XV+0602lbozbh2UrYIpciH14hnQ1UfJthIdRB07Y8=";
        String sign = "name=123";
        boolean flag = verify(signString,sign); //签名后和原文字符串
        System.out.println("验证结果:"+flag);
    } catch (Exception e) {
        e.printStackTrace();
    }
  }
}