RSA 加密算法 Java 公钥加密私钥解密 和 私钥加密公钥解密 的特点

package com.smt.cipher.unsymmetry;

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

import javax.crypto.Cipher;
import java.io.ByteArrayOutputStream;
import java.security.*;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;

public class RSAUtils {

    public static final String CHARSET = "UTF-8";
    public static final String RSA_ALGORITHM = "RSA";

    public static Map<String, String> createKeys(int keySize){
        //为RSA算法创建一个KeyPairGenerator对象
        KeyPairGenerator kpg;
        try{
            kpg = KeyPairGenerator.getInstance(RSA_ALGORITHM);
        }catch(NoSuchAlgorithmException e){
            throw new IllegalArgumentException("No such algorithm-->[" + RSA_ALGORITHM + "]");
        }

        //初始化KeyPairGenerator对象,密钥长度
        kpg.initialize(keySize);
        //生成密匙对
        KeyPair keyPair = kpg.generateKeyPair();
        //得到公钥
        Key publicKey = keyPair.getPublic();
        String publicKeyStr = Base64.encodeBase64URLSafeString(publicKey.getEncoded());
        //得到私钥
        Key privateKey = keyPair.getPrivate();
        String privateKeyStr = Base64.encodeBase64URLSafeString(privateKey.getEncoded());
        Map<String, String> keyPairMap = new HashMap<String, String>();
        keyPairMap.put("publicKey", publicKeyStr);
        keyPairMap.put("privateKey", privateKeyStr);

        return keyPairMap;
    }

    /**
     * 得到公钥
     * @param publicKey 密钥字符串（经过base64编码）
     * @throws Exception
     */
    public static RSAPublicKey getPublicKey(String publicKey) throws NoSuchAlgorithmException, InvalidKeySpecException {
        //通过X509编码的Key指令获得公钥对象
        KeyFactory keyFactory = KeyFactory.getInstance(RSA_ALGORITHM);
        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(Base64.decodeBase64(publicKey));
        RSAPublicKey key = (RSAPublicKey) keyFactory.generatePublic(x509KeySpec);
        return key;
    }

    /**
     * 得到私钥
     * @param privateKey 密钥字符串（经过base64编码）
     * @throws Exception
     */
    public static RSAPrivateKey getPrivateKey(String privateKey) throws NoSuchAlgorithmException, InvalidKeySpecException {
        //通过PKCS#8编码的Key指令获得私钥对象
        KeyFactory keyFactory = KeyFactory.getInstance(RSA_ALGORITHM);
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(Base64.decodeBase64(privateKey));
        RSAPrivateKey key = (RSAPrivateKey) keyFactory.generatePrivate(pkcs8KeySpec);
        return key;
    }

    /**
     * 公钥加密
     * @param data
     * @param publicKey
     * @return
     */
    public static String publicEncrypt(String data, RSAPublicKey publicKey){
        try{
            Cipher cipher = Cipher.getInstance(RSA_ALGORITHM);
            cipher.init(Cipher.ENCRYPT_MODE, publicKey);
            return Base64.encodeBase64URLSafeString(rsaSplitCodec(cipher, Cipher.ENCRYPT_MODE, data.getBytes(CHARSET), publicKey.getModulus().bitLength()));
        }catch(Exception e){
            throw new RuntimeException("加密字符串[" + data + "]时遇到异常", e);
        }
    }

    /**
     * 私钥解密
     * @param data
     * @param privateKey
     * @return
     */

    public static String privateDecrypt(String data, RSAPrivateKey privateKey){
        try{
            Cipher cipher = Cipher.getInstance(RSA_ALGORITHM);
            cipher.init(Cipher.DECRYPT_MODE, privateKey);
            return new String(rsaSplitCodec(cipher, Cipher.DECRYPT_MODE, Base64.decodeBase64(data), privateKey.getModulus().bitLength()), CHARSET);
        }catch(Exception e){
            throw new RuntimeException("解密字符串[" + data + "]时遇到异常", e);
        }
    }

    /**
     * 私钥加密
     * @param data
     * @param privateKey
     * @return
     */

    public static String privateEncrypt(String data, RSAPrivateKey privateKey){
        try{
            Cipher cipher = Cipher.getInstance(RSA_ALGORITHM);
            cipher.init(Cipher.ENCRYPT_MODE, privateKey);
            return Base64.encodeBase64URLSafeString(rsaSplitCodec(cipher, Cipher.ENCRYPT_MODE, data.getBytes(CHARSET), privateKey.getModulus().bitLength()));
        }catch(Exception e){
            throw new RuntimeException("加密字符串[" + data + "]时遇到异常", e);
        }
    }

    /**
     * 公钥解密
     * @param data
     * @param publicKey
     * @return
     */

    public static String publicDecrypt(String data, RSAPublicKey publicKey){
        try{
            Cipher cipher = Cipher.getInstance(RSA_ALGORITHM);
            cipher.init(Cipher.DECRYPT_MODE, publicKey);
            return new String(rsaSplitCodec(cipher, Cipher.DECRYPT_MODE, Base64.decodeBase64(data), publicKey.getModulus().bitLength()), CHARSET);
        }catch(Exception e){
            throw new RuntimeException("解密字符串[" + data + "]时遇到异常", e);
        }
    }

    private static byte[] rsaSplitCodec(Cipher cipher, int opmode, byte[] datas, int keySize){
        int maxBlock = 0;
        if(opmode == Cipher.DECRYPT_MODE){
            maxBlock = keySize / 8;
        }else{
            maxBlock = keySize / 8 - 11;
        }
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        int offSet = 0;
        byte[] buff;
        int i = 0;
        try{
            while(datas.length > offSet){
                if(datas.length-offSet > maxBlock){
                    buff = cipher.doFinal(datas, offSet, maxBlock);
                }else{
                    buff = cipher.doFinal(datas, offSet, datas.length-offSet);
                }
                out.write(buff, 0, buff.length);
                i++;
                offSet = i * maxBlock;
            }
        }catch(Exception e){
            throw new RuntimeException("加解密阀值为["+maxBlock+"]的数据时发生异常", e);
        }
        byte[] resultDatas = out.toByteArray();
        IOUtils.closeQuietly(out);
        return resultDatas;
    }

}

　　

为了方便使用 common-io 和  commons-codec

<dependencies>
<dependency>
<groupId>commons-io</groupId>
<artifactId>commons-io</artifactId>
<version>2.4</version>
</dependency>
<dependency>
<groupId>commons-codec</groupId>
<artifactId>commons-codec</artifactId>
<version>1.10</version>
</dependency>

</dependencies>

测试生成：

package com.smt.cipher;

import java.security.NoSuchAlgorithmException;
import java.util.Map;

import com.smt.cipher.unsymmetry.RSAUtils;

public class MainRSA {

	public static void main(String[] args) throws NoSuchAlgorithmException {
		Map<String,String> map  = RSAUtils.createKeys(1024);

		String publicKey = map.get("publicKey");
		String privateKey = map.get("privateKey");

		System.out.println( publicKey );
		System.out.println( privateKey );
	}

}

　　

结果:

生成的私钥 和 公钥 存下来 测试后面的 加解密：

package com.smt.cipher;

import java.security.NoSuchAlgorithmException;
import java.security.spec.InvalidKeySpecException;

import com.smt.cipher.unsymmetry.RSAUtils;

public class MainRSA2_use {

	static String  publicKey = "MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCnjjUJx1gMwqcwwRrMd4PjDOcuUE88QHlmr5zAEjSy8-4KY87A1XqpWNCMbfLOenPEFmfoc0HZdLxxlwHMpG1CAZPraUmKfDB4L3rI_qp67-R0n3KnnzPb2Hn0jFKlVbVJA7AHCgX2mXgz866VmSzHXX67gQkU29wmqOGCkajg8QIDAQAB";
	static String privateKey = "MIICdQIBADANBgkqhkiG9w0BAQEFAASCAl8wggJbAgEAAoGBAKeONQnHWAzCpzDBGsx3g-MM5y5QTzxAeWavnMASNLLz7gpjzsDVeqlY0Ixt8s56c8QWZ-hzQdl0vHGXAcykbUIBk-tpSYp8MHgvesj-qnrv5HSfcqefM9vYefSMUqVVtUkDsAcKBfaZeDPzrpWZLMddfruBCRTb3Cao4YKRqODxAgMBAAECgYBo46rsHjBOfKQw7xGZoc-cGP23jmqrqyjUUWbtDfiTdgQz2Nsa-Ai7bm_PGR0AiMNjoysU5uH4AQ3ehcuIkf4aZUBeJrbI05-nv5U1WBfWCtcgXJlt75TJ_Nm0gZ1OIGyXlPw152EgED4e7PR6Ql1C88lVOUGblR1mU5dDkGNcyQJBAP2lp2EgZWdTrlmSB-GxuQlF4nJO6W7qpa7-pKUSMAvW8M8B1m3qnypUrtxyY4gHTS0paag7apOCzN-o2BV0sP8CQQCpHButedrsZk7p1Wecm9GfDWwgeU09QrMjTlnhBocy6d0LXF29WMiUrVcrp-1I-NDnr6Fgp38Vz9Noqr_6S34PAkAHONI9N7jrajyKnFfRG0hTdUPvUUPgPpodE28IrC3mCGau3jSGyKljgSnBaRhgZSTTZlx1x8tPC-hdbedJJRttAkAo6Bi13O0dFB5wp-OZWYPacpe-Pzl04SaOGszZBwg7Q6Dpt50hSVGzzT5x2_wlE7MM6EokJEA0mYItJmir9gj3AkBks-kzn-DT3tKeTpFjJsCOmo1RrSzhFZV48aZqw6TSuRyuspJ0mMfwKY95MtdoD2RxGnW77uecLOjwO1HGh3Ly";

	public static void main(String[] args) throws NoSuchAlgorithmException, InvalidKeySpecException {

		String ciphertext = RSAUtils.privateEncrypt("测试数RSA",  RSAUtils.getPrivateKey(privateKey  ) );
		System.out.println( ciphertext );
		System.out.println( RSAUtils.publicDecrypt(ciphertext,  RSAUtils.getPublicKey(publicKey) ) );

	}

}

　　

私钥加密公钥解密的的测试结果:

同理 公钥加密私钥解密的 结果类似。

备注：私钥只有自己持有，公钥交给需要公约的人，也就是说，私钥只有一个人持有，公钥是公开的可能有很多人都有。

　　   并且私钥加密的数据，只能对应的公钥来揭开，公钥加密的数据只能对应的私钥来解密。

　　　私钥加密，公钥解密的特点是 保证数据不被修改(因为只有私钥能加密，所以公钥正常解密得到的数据一定是私钥正常发出的，并且没有别篡改的，当然前提是 私钥没有被泄露，泄露了还叫个毛的私钥 )。

　　　公钥加密私钥解密的特点是保证数据不被泄漏（因为公钥加密的数据，只能被私钥解密，所以 公钥加密的数据即便被别人获取了也不能解开，信息自然就不会被泄露 。

　　　

代码git 下载地址:https://github.com/hualiuwuxin/tools.git