源码地址放在文章末尾

package Mr.He;

import javax.crypto.Cipher;
import java.security.*;
import java.util.Base64;
import java.util.HashMap;
import java.util.Map;

/**
 * RSA加密演示
 * @author wishforyou.xia@gmail.com
 * @date 2019/7/3 23:22
 */
public class RsaDemo {
    private static final String STRING = "missyou";

    public static void main(String[] args) throws Exception {
        Map<String, Key> keyMap = createKey();
        String publicKeyString = keyToString(keyMap.get("publicKay"));
        String privateKeyString = keyToString(keyMap.get("privateKey"));
        System.out.println("公钥：" + publicKeyString);
        System.out.println("私钥：" + privateKeyString);

        String encodeStr = encode(keyMap.get("publicKay"));
        System.err.println("加密后的字符串为:" + encodeStr);

        String decodeStr = decode(keyMap.get("privateKey"),encodeStr);
        System.out.println("还原后的字符串为:" + decodeStr);

    }

    private static String decode(Key key,String encodeStr) throws Exception {
        /**
         * 使用字符串作为密钥时需要转回key
         * String keyString = new String(Base64.getEncoder().encode(key.getEncoded()));
         * byte[] keyByte = Base64.getDecoder().decode(keyString);
         * RSAPrivateKey priKey = (RSAPrivateKey) KeyFactory.getInstance("RSA").generatePrivate(new PKCS8EncodedKeySpec(keyByte));
         *
         */

        byte[] strByte = Base64.getDecoder().decode(encodeStr);
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.DECRYPT_MODE,key);
        byte[] decodeByte = cipher.doFinal(strByte);
        String decodeString = new String(decodeByte);
        return decodeString;
    }

    private static String encode(Key key) throws Exception {
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.ENCRYPT_MODE,key);
        byte[] encodeByte = cipher.doFinal(STRING.getBytes("UTF-8"));
        byte[] base64Byte = Base64.getEncoder().encode(encodeByte);
        String string = new String(base64Byte);
        return string;
    }

    private static Map<String, Key> createKey() throws NoSuchAlgorithmException {
        KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA");
        keyPairGen.initialize(512,new SecureRandom("missyou".getBytes()));
        KeyPair keyPair = keyPairGen.generateKeyPair();
        PublicKey publicKey = keyPair.getPublic();
        PrivateKey privateKey = keyPair.getPrivate();
        Map<String, Key> key = new HashMap<>(2);
        key.put("publicKay",publicKey);
        key.put("privateKey",privateKey);
        return key;
    }

    private static <T extends Key> String keyToString(T key){
         byte[] keyByte = key.getEncoded();
         String keyString = new String (Base64.getEncoder().encode(keyByte));
         return keyString;
    }

}

/**
*  源码地址github
*/
https://github.com/HeQuanX/learning