非对称加密RSA工具类-RSAUtil.class

非对称加密RSA工具类-RSAUtil.class

RSA加解密工具类，如果使用模数的指数来生成公钥和私钥时，建议重新生成自己的模数和公钥指数、私钥指数。可取消 main 方法注释运行生成。

import javax.crypto.Cipher;
import java.math.BigInteger;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.RSAPrivateKeySpec;
import java.security.spec.RSAPublicKeySpec;

/**
 * @name: RSAUtil
 * @desc: RSA 加解密工具类
 **/
public class RSAUtil {

    public static final String RSA = "RSA";
    public static final int KEY_SIZE = 1024;
    /*模数*/
    public static String MODULUS = "";
    /*公钥指数*/
    public static String PUBLIC_EXPONENT = "";
    /*私钥指数*/
    public static String PRIVATE_EXPONENT = "";

    /**
     * 公钥加密
     *
     * @param data 明文
     * @return String 密文
     * @throws Exception Exception
     */
    public static String encryptByPublicKey(String data) throws Exception {
        RSAPublicKey publicKey = getPublicKey(MODULUS, PUBLIC_EXPONENT);
        return encryptByPublicKey(data, publicKey);
    }

    /**
     * 公钥加密
     *
     * @param data      明文
     * @param publicKey 公钥
     * @return String 密文
     * @throws Exception Exception
     */
    public static String encryptByPublicKey(String data, RSAPublicKey publicKey) throws Exception {
        Cipher cipher = Cipher.getInstance(RSA);
        cipher.init(Cipher.ENCRYPT_MODE, publicKey);
        // 模长
        int key_len = publicKey.getModulus().bitLength() / 8;
        // 加密数据长度 <= 模长-11
        String[] datas = splitString(data, key_len - 11);
        StringBuilder sb = new StringBuilder();
        // 如果明文长度大于模长-11则要分组加密
        for (String s : datas) {
            sb.append(bcd2Str(cipher.doFinal(s.getBytes())));
        }
        return sb.toString();
    }

    /**
     * 私钥解密
     *
     * @param data 密文
     * @return String 明文
     * @throws Exception Exception
     */
    public static String decryptByPrivateKey(String data) throws Exception {
        RSAPrivateKey privateKey = getPrivateKey(MODULUS, PRIVATE_EXPONENT);
        return decryptByPrivateKey(data, privateKey);
    }

    /**
     * 私钥解密
     *
     * @param data       密文
     * @param privateKey 私钥
     * @return String 明文
     * @throws Exception Exception
     */
    public static String decryptByPrivateKey(String data, RSAPrivateKey privateKey) throws Exception {
        Cipher cipher = Cipher.getInstance(RSA);
        cipher.init(Cipher.DECRYPT_MODE, privateKey);
        // 模长
        int key_len = privateKey.getModulus().bitLength() / 8;
        byte[] bytes = data.getBytes();
        byte[] bcd = ASCII_To_BCD(bytes, bytes.length);
        // 如果密文长度大于模长则要分组解密
        StringBuilder sb = new StringBuilder();
        byte[][] arrays = splitArray(bcd, key_len);
        for (byte[] arr : arrays) {
            sb.append(new String(cipher.doFinal(arr)));
        }
        return sb.toString();
    }


    /**
     * 生成公钥和私钥对
     *
     * @return KeyPair
     * @throws Exception Exception
     */
    public static RSAKeyPair genKeyPair() throws Exception {
        KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance(RSA);
        keyPairGen.initialize(KEY_SIZE);
        KeyPair keyPair = keyPairGen.generateKeyPair();
        // 公钥
        RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
        // 私钥
        RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();
        return new RSAKeyPair(publicKey, privateKey);
    }

    /**
     * 使用模和指数生成RSA公钥
     * 注意：【此代码用了默认补位方式，为RSA/None/PKCS1Padding，不同JDK默认的补位方式可能不同，如Android默认是RSA
     * /None/NoPadding】
     *
     * @return RSAPublicKey
     * @throws Exception Exception
     */
    public static RSAPublicKey getPublicKey() throws Exception {
        return getPublicKey(MODULUS, PUBLIC_EXPONENT);
    }

    /**
     * 使用模和指数生成RSA公钥
     * 注意：【此代码用了默认补位方式，为RSA/None/PKCS1Padding，不同JDK默认的补位方式可能不同，如Android默认是RSA
     * /None/NoPadding】
     *
     * @param modulus  模
     * @param exponent 指数
     * @return RSAPublicKey
     * @throws Exception Exception
     */
    public static RSAPublicKey getPublicKey(String modulus, String exponent) throws Exception {
        BigInteger b1 = new BigInteger(modulus);
        BigInteger b2 = new BigInteger(exponent);
        KeyFactory keyFactory = KeyFactory.getInstance(RSA);
        RSAPublicKeySpec keySpec = new RSAPublicKeySpec(b1, b2);
        return (RSAPublicKey) keyFactory.generatePublic(keySpec);
    }

    /**
     * 使用模和指数生成RSA私钥
     * 注意：【此代码用了默认补位方式，为RSA/None/PKCS1Padding，不同JDK默认的补位方式可能不同，如Android默认是RSA
     * /None/NoPadding】
     *
     * @return RSAPrivateKey
     * @throws Exception Exception
     */
    public static RSAPrivateKey getPrivateKey() throws Exception {
        return getPrivateKey(MODULUS, PRIVATE_EXPONENT);
    }

    /**
     * 使用模和指数生成RSA私钥
     * 注意：【此代码用了默认补位方式，为RSA/None/PKCS1Padding，不同JDK默认的补位方式可能不同，如Android默认是RSA
     * /None/NoPadding】
     *
     * @param modulus  模
     * @param exponent 指数
     * @return RSAPrivateKey
     * @throws Exception Exception
     */
    public static RSAPrivateKey getPrivateKey(String modulus, String exponent) throws Exception {
        BigInteger b1 = new BigInteger(modulus);
        BigInteger b2 = new BigInteger(exponent);
        KeyFactory keyFactory = KeyFactory.getInstance(RSA);
        RSAPrivateKeySpec keySpec = new RSAPrivateKeySpec(b1, b2);
        return (RSAPrivateKey) keyFactory.generatePrivate(keySpec);
    }

    /**
     * ASCII码转BCD码
     */
    public static byte[] ASCII_To_BCD(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] = asc_to_bcd(ascii[j++]);
            bcd[i] = (byte) (((j >= asc_len) ? 0x00 : asc_to_bcd(ascii[j++])) + (bcd[i] << 4));
        }
        return bcd;
    }

    public static byte asc_to_bcd(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;
    }

    /**
     * BCD转字符串
     */
    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);
    }

    /**
     * 拆分字符串
     */
    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;
    }

    /**
     * 拆分数组
     */
    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;
    }

    /**
     * @desc RSA公钥私钥对
     * @date 2021/12/29 17:08
     */
    public static class RSAKeyPair {
        /**
         * 公钥
         */
        private RSAPublicKey publicKey;
        /**
         * 私钥
         */
        private RSAPrivateKey privateKey;

        public RSAKeyPair() {
        }

        public RSAKeyPair(RSAPublicKey publicKey, RSAPrivateKey privateKey) {
            this.publicKey = publicKey;
            this.privateKey = privateKey;
        }

        public RSAPublicKey getPublicKey() {
            return publicKey;
        }

        public void setPublicKey(RSAPublicKey publicKey) {
            this.publicKey = publicKey;
        }

        public RSAPrivateKey getPrivateKey() {
            return privateKey;
        }

        public void setPrivateKey(RSAPrivateKey privateKey) {
            this.privateKey = privateKey;
        }
    }

    public static void main(String[] args) throws Exception {

//        KeyPairGenerator generator = KeyPairGenerator.getInstance("RSA");
//        generator.initialize(1024);
//        KeyPair pair = generator.generateKeyPair();
//        RSAPrivateKey privateKey = (RSAPrivateKey) pair.getPrivate();
//        RSAPublicKey publicKey = (RSAPublicKey) pair.getPublic();
//        System.out.println("publicKey exponent:" + publicKey.getPublicExponent());
//        System.out.println("publicKey modules:" + publicKey.getModulus());
//        System.out.println("publicKey format:" + publicKey.getFormat());
//        System.out.println("---------------------分割线-------------------------");
//        System.out.println("privateKey exponent:" + privateKey.getPrivateExponent());
//        System.out.println("privateKey modules:" + privateKey.getModulus());
//        System.out.println("privateKey format:" + privateKey.getFormat());

//        RSAKeyPair rsaKeyPair = genKeyPair();
//        RSAPublicKey publicKey = rsaKeyPair.getPublicKey();
//        RSAPrivateKey privateKey = rsaKeyPair.getPrivateKey();
//        //模
//        String MODULUS = publicKey.getModulus().toString();
//        System.err.println("模数:" + MODULUS);
//        //公钥指数
//        String PUBLIC_EXPONENT = publicKey.getPublicExponent().toString();
//        System.err.println("公钥指数:" + PUBLIC_EXPONENT);
//        //私钥指数
//        String PRIVATE_EXPONENT = privateKey.getPrivateExponent().toString();
//        System.err.println("私钥指数:" + PRIVATE_EXPONENT);
//        //明文
//        String ming = "Hello World";
//        //使用模和指数生成公钥和私钥
//        RSAPublicKey pubKey = RSAUtil.getPublicKey(MODULUS, PUBLIC_EXPONENT);
//        RSAPrivateKey priKey = RSAUtil.getPrivateKey(MODULUS, PRIVATE_EXPONENT);
//
//        //加密后的密文
//        String mi = RSAUtil.encryptByPublicKey(ming, pubKey);
//        System.err.println("加密后：" + mi);
//        //解密后的明文
//        ming = RSAUtil.decryptByPrivateKey(mi, priKey);
//        System.err.println("解密后:" + ming);

    }
}