如何用java RSA生成生成公钥私钥（非对称加密）

我会带着你远行 2022-05-29 01:07 221阅读 0赞

言简意赅，直接见代码：

package com;
    
    
    import java.security.Key;
    import java.security.KeyFactory;
    import java.security.KeyPair;
    import java.security.KeyPairGenerator;
    import java.security.PrivateKey;
    import java.security.PublicKey;
    import java.security.SecureRandom;
    import java.security.Signature;
    import java.security.interfaces.RSAPrivateKey;
    import java.security.interfaces.RSAPublicKey;
    import java.security.spec.PKCS8EncodedKeySpec;
    import java.security.spec.X509EncodedKeySpec;
    import java.util.Date;
    import java.util.HashMap;
    import java.util.Map;
    
    
    import javax.crypto.Cipher;
    
    
    import sun.misc.BASE64Decoder;
    import sun.misc.BASE64Encoder;
    
    
    public class CreateSecretKey {
        public static final String KEY_ALGORITHM = "RSA";
        private static final String PUBLIC_KEY = "RSAPublicKey";
        private static final String PRIVATE_KEY = "RSAPrivateKey";
        public static final String SIGNATURE_ALGORITHM="MD5withRSA";
         /**
         * 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;
        //获得公钥字符串
        public static String getPublicKeyStr(Map<String, Object> keyMap) throws Exception {
            //获得map中的公钥对象 转为key对象
            Key key = (Key) keyMap.get(PUBLIC_KEY);
            //编码返回字符串
            return encryptBASE64(key.getEncoded());
        }
    
    
        //获得私钥字符串
        public static String getPrivateKeyStr(Map<String, Object> keyMap) throws Exception {
            //获得map中的私钥对象 转为key对象
            Key key = (Key) keyMap.get(PRIVATE_KEY);
            //编码返回字符串
            return encryptBASE64(key.getEncoded());
        }
        
        //获取公钥
        public static PublicKey getPublicKey(String key) throws Exception {  
            byte[] keyBytes;  
            keyBytes = (new BASE64Decoder()).decodeBuffer(key);  
            X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);  
            KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);  
            PublicKey publicKey = keyFactory.generatePublic(keySpec);  
            return publicKey;  
        }  
        
        //获取私钥
        public static PrivateKey getPrivateKey(String key) throws Exception {  
            byte[] keyBytes;  
            keyBytes = (new BASE64Decoder()).decodeBuffer(key);  
            PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(keyBytes);  
            KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);  
            PrivateKey privateKey = keyFactory.generatePrivate(keySpec);  
            return privateKey;  
        }
        
        //解码返回byte
        public static byte[] decryptBASE64(String key) throws Exception {
            return (new BASE64Decoder()).decodeBuffer(key);
        }
    
    
        //编码返回字符串
        public static String encryptBASE64(byte[] key) throws Exception {
            return (new BASE64Encoder()).encodeBuffer(key);
        }
        
        //***************************签名和验证*******************************  
        public static byte[] sign(byte[] data,String privateKeyStr) throws Exception{  
          PrivateKey priK = getPrivateKey(privateKeyStr);  
          Signature sig = Signature.getInstance(SIGNATURE_ALGORITHM);       
          sig.initSign(priK);  
          sig.update(data);  
          return sig.sign();  
        }  
        
        public static boolean verify(byte[] data,byte[] sign,String publicKeyStr) throws Exception{  
          PublicKey pubK = getPublicKey(publicKeyStr);  
          Signature sig = Signature.getInstance(SIGNATURE_ALGORITHM);  
          sig.initVerify(pubK);  
          sig.update(data);  
          return sig.verify(sign);  
        }  
        
      //************************加密解密**************************  
        public static byte[] encrypt(byte[] plainText,String publicKeyStr)throws Exception{  
            PublicKey publicKey = getPublicKey(publicKeyStr);  
            Cipher cipher = Cipher.getInstance(KEY_ALGORITHM);  
            cipher.init(Cipher.ENCRYPT_MODE, publicKey);  
            int inputLen = plainText.length;
            ByteArrayOutputStream out = new ByteArrayOutputStream();
            int offSet = 0;
            int i = 0;
            byte[] cache;
            while (inputLen - offSet > 0) {
                if (inputLen - offSet > MAX_ENCRYPT_BLOCK) {
                    cache = cipher.doFinal(plainText, offSet, MAX_ENCRYPT_BLOCK);
                } else {
                    cache = cipher.doFinal(plainText, offSet, inputLen - offSet);
                }
                out.write(cache, 0, cache.length);
                i++;
                offSet = i * MAX_ENCRYPT_BLOCK;
            }
            byte[] encryptText = out.toByteArray();
            out.close();  
            return encryptText;  
        }  
          
        public static byte[] decrypt(byte[] encryptText,String privateKeyStr)throws Exception{  
            PrivateKey privateKey = getPrivateKey(privateKeyStr);  
            Cipher cipher = Cipher.getInstance(KEY_ALGORITHM);  
            cipher.init(Cipher.DECRYPT_MODE, privateKey);  
            int inputLen = encryptText.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(encryptText, offSet, MAX_DECRYPT_BLOCK);
                } else {
                    cache = cipher.doFinal(encryptText, offSet, inputLen - offSet);
                }
                out.write(cache, 0, cache.length);
                i++;
                offSet = i * MAX_DECRYPT_BLOCK;
            }
            byte[] plainText = out.toByteArray();
            out.close();  
            return plainText;  
        }  
    
    
        public static void main(String[] args) {
            Map<String, Object> keyMap;
            byte[] cipherText;
            String input = "Hello World!";
            try {
                keyMap = initKey();
                String publicKey = getPublicKeyStr(keyMap);
                System.out.println("公钥------------------");
                System.out.println(publicKey);
                String privateKey = getPrivateKeyStr(keyMap);
                System.out.println("私钥------------------");
                System.out.println(privateKey);
                
                System.out.println("测试可行性-------------------");
                System.out.println("明文======="+input);
                
                cipherText = encrypt(input.getBytes(),publicKey); 
                //加密后的东西 
                System.out.println("密文======="+new String(cipherText));
                //开始解密 
                byte[] plainText = decrypt(cipherText,privateKey); 
                System.out.println("解密后明文===== " + new String(plainText));
                System.out.println("验证签名-----------");
                
                String str="被签名的内容";  
                System.out.println("\n原文:"+str);  
                byte[] signature=sign(str.getBytes(),privateKey);  
                boolean status=verify(str.getBytes(), signature,publicKey);  
                System.out.println("验证情况："+status);  
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    
    
    }