RSA工具类-非堆成加解密

1.maven依赖
<dependency>
    <groupId>commons-codec</groupId>
    <artifactId>commons-codec</artifactId>
    <version>1.10</version>
</dependency>

2.代码
package com.liftsail.rsademo.utils;

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

import javax.crypto.Cipher;
import java.io.BufferedReader;
import java.io.ByteArrayOutputStream;
import java.io.FileInputStream;
import java.io.InputStreamReader;
import java.security.*;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;

/**
 * @Author 张帆
 * @Description 不积跬步无以至千里
 * @Date 2022/10/28 20:29
 */
public class RSAUtil {

    /**
     * RSA最大加密明文大小
     */
    private static final int MAX_ENCRYPT_BLOCK = 117;

    /**
     * RSA最大解密密文大小
     */
    private static final int MAX_DECRYPT_BLOCK = 128;

    /**
     * 获取密钥对
     *
     * @return 密钥对
     */
    public static KeyPair getKeyPair() throws Exception {
        KeyPairGenerator generator = KeyPairGenerator.getInstance("RSA");
        generator.initialize(1024);
        return generator.generateKeyPair();
    }

    /**
     * 获取私钥
     *
     * @param privateKey 私钥字符串
     * @return
     */
    public static PrivateKey getPrivateKey(String privateKey) throws Exception {
        KeyFactory keyFactory = KeyFactory.getInstance("RSA");
        byte[] decodedKey = Base64.decodeBase64(privateKey.getBytes());
        PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(decodedKey);
        return keyFactory.generatePrivate(keySpec);
    }

    /**
     * 获取公钥
     *
     * @param publicKey 公钥字符串
     * @return
     */
    public static PublicKey getPublicKey(String publicKey) throws Exception {
        KeyFactory keyFactory = KeyFactory.getInstance("RSA");
        byte[] decodedKey = Base64.decodeBase64(publicKey.getBytes());
        X509EncodedKeySpec keySpec = new X509EncodedKeySpec(decodedKey);
        return keyFactory.generatePublic(keySpec);
    }

    /**
     * RSA加密
     *
     * @param data      待加密数据
     * @param publicKey 公钥
     * @return
     */
    public static String encrypt(String data, PublicKey publicKey) throws Exception {
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.ENCRYPT_MODE, publicKey);
        int inputLen = data.getBytes().length;
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        int offset = 0;
        byte[] cache;
        int i = 0;
        // 对数据分段加密
        while (inputLen - offset > 0) {
            if (inputLen - offset > MAX_ENCRYPT_BLOCK) {
                cache = cipher.doFinal(data.getBytes(), offset, MAX_ENCRYPT_BLOCK);
            } else {
                cache = cipher.doFinal(data.getBytes(), offset, inputLen - offset);
            }
            out.write(cache, 0, cache.length);
            i++;
            offset = i * MAX_ENCRYPT_BLOCK;
        }
        byte[] encryptedData = out.toByteArray();
        out.close();
        // 获取加密内容使用base64进行编码,并以UTF-8为标准转化成字符串
        // 加密后的字符串
        return new String(Base64.encodeBase64String(encryptedData));
    }

    /**
     * RSA解密
     *
     * @param data       待解密数据
     * @param privateKey 私钥
     * @return
     */
    public static String decrypt(String data, PrivateKey privateKey) throws Exception {
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.DECRYPT_MODE, privateKey);
        byte[] dataBytes = Base64.decodeBase64(data);
        int inputLen = dataBytes.length;
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        int offset = 0;
        byte[] cache;
        int i = 0;
        // 对数据分段解密
        while (inputLen - offset > 0) {
            if (inputLen - offset > MAX_DECRYPT_BLOCK) {
                cache = cipher.doFinal(dataBytes, offset, MAX_DECRYPT_BLOCK);
            } else {
                cache = cipher.doFinal(dataBytes, offset, inputLen - offset);
            }
            out.write(cache, 0, cache.length);
            i++;
            offset = i * MAX_DECRYPT_BLOCK;
        }
        byte[] decryptedData = out.toByteArray();
        out.close();
        // 解密后的内容
        return new String(decryptedData, "UTF-8");
    }

    /**
     * 签名
     *
     * @param data       待签名数据
     * @param privateKey 私钥
     * @return 签名
     */
    public static String sign(String data, PrivateKey privateKey) throws Exception {
        byte[] keyBytes = privateKey.getEncoded();
        PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance("RSA");
        PrivateKey key = keyFactory.generatePrivate(keySpec);
        Signature signature = Signature.getInstance("MD5withRSA");
        signature.initSign(key);
        signature.update(data.getBytes());
        return new String(Base64.encodeBase64(signature.sign()));
    }

    /**
     * 验签
     *
     * @param srcData   原始字符串
     * @param publicKey 公钥
     * @param sign      签名
     * @return 是否验签通过
     */
    public static boolean verify(String srcData, PublicKey publicKey, String sign) throws Exception {
        byte[] keyBytes = publicKey.getEncoded();
        X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance("RSA");
        PublicKey key = keyFactory.generatePublic(keySpec);
        Signature signature = Signature.getInstance("MD5withRSA");
        signature.initVerify(key);
        signature.update(srcData.getBytes());
        return signature.verify(Base64.decodeBase64(sign.getBytes()));
    }

    //读取文件成字符串
    public static String file2str(String path, String encoder) {
        StringBuilder sb = new StringBuilder();
        try {
            BufferedReader in = new BufferedReader(new InputStreamReader(new FileInputStream(path), encoder));
            String str = new String();
            while ((str = in.readLine()) != null) {
                sb.append(str);
            }
            in.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return sb.toString();
    }

    public static void main(String[] args) {
        String s = file2str("C:\\Users\\张帆\\Downloads\\private_key.pem", "utf-8");
        try {
            System.out.println(getPrivateKey(s));
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

//    public static void main(String[] args) {
//        try {
//            // 生成密钥对
//            KeyPair keyPair = getKeyPair();
////            String privateKey = new String(Base64.encodeBase64(keyPair.getPrivate().getEncoded()));
//            String privateKey = "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";
////            String publicKey = new String(Base64.encodeBase64(keyPair.getPublic().getEncoded()));
//            String publicKey = "MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCG9wdOeB/mMPO8ns7sGldDPk17YaAZlrShynq+TPbtf7f9P+WcAQxGlp8KMD8oZB1rGZOxD2i/C4LJdIePw1ICax+dMumb2JlYLpcQ9xA3uOocsMwTutoU9sMRGwEZjfvI//9cZE2F1cbu7GzVeXfuEsQEntvTgaq7pGMrPjSriQIDAQAB";
//            System.out.println("私钥:" + privateKey);
//            System.out.println("公钥:" + publicKey);
//            // RSA加密
//            String data = "test";
//            String encryptData = encrypt(data, getPublicKey(publicKey));
//            System.out.println("加密后内容:" + encryptData);
//            // RSA解密
//            String decryptData = decrypt(encryptData, getPrivateKey(privateKey));
//            System.out.println("解密后内容:" + decryptData);
//            // RSA签名
//            String sign = sign(data, getPrivateKey(privateKey));
//            // RSA验签
//            boolean result = verify(data, getPublicKey(publicKey), sign);
//            System.out.print("验签结果:" + result);
//        } catch (Exception e) {
//            e.printStackTrace();
//            System.out.print("加解密异常");
//        }
//    }
}

原文地址：http://www.cnblogs.com/liftsail/p/16921558.html