OpenSSL文档阅读笔记-RSA Encryption & Decryption Example with OpenSSL in C

Posted 2022-08-27 IT1995

tags:

篇首语：本文由小常识网(cha138.com)小编为大家整理，主要介绍了OpenSSL文档阅读笔记-RSA Encryption & Decryption Example with OpenSSL in C相关的知识，希望对你有一定的参考价值。

这篇博文有点老了是2014年3月19日的。但效果还是杠杆的。

这篇博文说明如何调用OpenSSL进行RSA加解密。编程语言用的是C。

本博文小节：

①使用OpenSSL生成RSA密钥；

②使用公钥加密，私钥解密；

③使用私钥加密，公钥解密；

④加解密示例代码。

使用OpenSSL生成RSA密钥

使用下面的命令试生产2048位的RSA私钥

openssl genrsa -out private.pem 2048

从私钥中提取公钥：

openssl rsa -in private.pem -outform PEM -pubout -out public.pem

注意生成的证书都是pem格式，这个是用ASCII存的，Base64编码的格式。

使用公钥加密，私钥解密

对应的API函数分别为：

int RSA_public_encrypt(int flen, unsigned char *from,
   unsigned char *to, RSA *rsa, int padding);
 
int RSA_private_decrypt(int flen, unsigned char *from,
    unsigned char *to, RSA *rsa, int padding);

这里的编程逻辑是先构造一个RSA结构体：

RSA * createRSA(unsigned char * key,int public)

    RSA *rsa= NULL;
    BIO *keybio ;
    keybio = BIO_new_mem_buf(key, -1);
    if (keybio==NULL)
    
        printf( "Failed to create key BIO");
        return 0;
    
    if(public)
    
        rsa = PEM_read_bio_RSA_PUBKEY(keybio, &rsa,NULL, NULL);
    
    else
    
        rsa = PEM_read_bio_RSAPrivateKey(keybio, &rsa,NULL, NULL);
    
 
    return rsa;

这样就能直接创建公钥和私钥了

createRSA(“PUBLIC_KEY_BUFFER”,1);
createRSA(“PRIVATE_KEY_BUFFER”,0);

如果需要保存密钥为文件可以用如下代码：

RSA * createRSAWithFilename(char * filename,int public)

    FILE * fp = fopen(filename,"rb");
 
    if(fp == NULL)
    
        printf("Unable to open file %s \\n",filename);
        return NULL;    
    
    RSA *rsa= RSA_new() ;
 
    if(public)
    
        rsa = PEM_read_RSA_PUBKEY(fp, &rsa,NULL, NULL);
    
    else
    
        rsa = PEM_read_RSAPrivateKey(fp, &rsa,NULL, NULL);
    
 
    return rsa;

公钥加密有如下几种填充方式：

RSA_PKCS1_PADDING：当下最流行的填充方式。

RSA_PKCS1_OAEP_PADDING：推荐目前开发的应用都使用这种加密方式。

RSA_SSLV23_PADDING：与第一种类似，但多出代表服务器支持SSL3.

RSA_NO_PADDING：别用这种，不好。

下面是使用密钥来加密数据：

int padding = RSA_PKCS1_PADDING;
 
int public_encrypt(unsigned char * data,int data_len,unsigned char * key, unsigned char *encrypted)

    RSA * rsa = createRSA(key,1);
    int result = RSA_public_encrypt(data_len,data,encrypted,rsa,padding);
    return result;

私钥解密

使用如下代码进行解密：

int private_decrypt(unsigned char * enc_data,int data_len,unsigned char * key, unsigned char *decrypted)

    RSA * rsa = createRSA(key,0);
    int  result = RSA_private_decrypt(data_len,enc_data,decrypted,rsa,padding);
    return result;

使用私钥加密，公钥解密

私钥加密其实就是签名的过程，下面分别对应私钥加密，公钥解密的API。

int RSA_private_encrypt(int flen, unsigned char *from,
   unsigned char *to, RSA *rsa, int padding);
 
int RSA_public_decrypt(int flen, unsigned char *from,
   unsigned char *to, RSA *rsa, int padding);

私钥加密只支持两种模式：RSA_PKCS1_PADDIN和RSA_NO_PADDING。

私钥加密：

int private_encrypt(unsigned char * data,int data_len,unsigned char * key, unsigned char *encrypted)

    RSA * rsa = createRSA(key,0);
    int result = RSA_private_encrypt(data_len,data,encrypted,rsa,padding);
    return result;

公钥解密：

int public_decrypt(unsigned char * enc_data,int data_len,unsigned char * key, unsigned char *decrypted)

    RSA * rsa = createRSA(key,1);
    int  result = RSA_public_decrypt(data_len,enc_data,decrypted,rsa,padding);
    return result;

加解密示例代码

下面是一个完整的代码：

RSAEncryptionAndDecryption.pro

QT += core
QT -= gui

TARGET = RSAEncryptionAndDecryption
CONFIG += console
CONFIG -= app_bundle

QMAKE_CFLAGS = -fpermissive
QMAKE_CXXFLAGS = -fpermissive
QMAKE_LFLAGS = -fpermissive

INCLUDEPATH += /usr/local/ssl/include
LIBS += -L /usr/local/ssl/lib/ -lssl -lcrypto


TEMPLATE = app

SOURCES += main.cpp

main.cpp

#include <QCoreApplication>
#include <openssl/pem.h>
#include <openssl/ssl.h>
#include <openssl/rsa.h>
#include <openssl/evp.h>
#include <openssl/bio.h>
#include <openssl/err.h>

int padding = RSA_PKCS1_PADDING;

RSA * createRSA(unsigned char * key,int isPublic)

    RSA *rsa= NULL;
    BIO *keybio ;
    keybio = BIO_new_mem_buf(key, -1);
    if (keybio==NULL)

        printf( "Failed to create key BIO");
        return 0;
    
    if(isPublic)

        rsa = PEM_read_bio_RSA_PUBKEY(keybio, &rsa,NULL, NULL);
    
    else

        rsa = PEM_read_bio_RSAPrivateKey(keybio, &rsa,NULL, NULL);
    
    if(rsa == NULL)

        printf( "Failed to create RSA");
        return NULL;
    

    return rsa;


int public_encrypt(unsigned char * data,int data_len,unsigned char * key, unsigned char *encrypted)

    RSA * rsa = createRSA(key,1);
    int result = RSA_public_encrypt(data_len,data,encrypted,rsa,padding);
    return result;

int private_decrypt(unsigned char * enc_data,int data_len,unsigned char * key, unsigned char *decrypted)

    RSA * rsa = createRSA(key,0);
    int  result = RSA_private_decrypt(data_len,enc_data,decrypted,rsa,padding);
    return result;



int private_encrypt(unsigned char * data,int data_len,unsigned char * key, unsigned char *encrypted)

    RSA * rsa = createRSA(key,0);
    int result = RSA_private_encrypt(data_len,data,encrypted,rsa,padding);
    return result;

int public_decrypt(unsigned char * enc_data,int data_len,unsigned char * key, unsigned char *decrypted)

    RSA * rsa = createRSA(key,1);
    int  result = RSA_public_decrypt(data_len,enc_data,decrypted,rsa,padding);
    return result;


void printLastError(char *msg)

     rchar * err = malloc(130);;
    ERR_load_crypto_strings();
    ERR_error_string(ERR_get_error(), err);
    printf("%s ERROR: %s\\n",msg, err);
    free(err);



int main(int argc, char *argv[])

    char plainText[2048/8] = "Hello this is Ravi"; //key length : 2048

   char publicKey[]="-----BEGIN PUBLIC KEY-----\\n"\\
  "MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAy8Dbv8prpJ/0kKhlGeJY\\n"\\
  "ozo2t60EG8L0561g13R29LvMR5hyvGZlGJpmn65+A4xHXInJYiPuKzrKUnApeLZ+\\n"\\
  "vw1HocOAZtWK0z3r26uA8kQYOKX9Qt/DbCdvsF9wF8gRK0ptx9M6R13NvBxvVQAp\\n"\\
  "fc9jB9nTzphOgM4JiEYvlV8FLhg9yZovMYd6Wwf3aoXK891VQxTr/kQYoq1Yp+68\\n"\\
  "i6T4nNq7NWC+UNVjQHxNQMQMzU6lWCX8zyg3yH88OAQkUXIXKfQ+NkvYQ1cxaMoV\\n"\\
  "PpY72+eVthKzpMeyHkBn7ciumk5qgLTEJAfWZpe4f4eFZj/Rc8Y8Jj2IS5kVPjUy\\n"\\
  "wQIDAQAB\\n"\\
  "-----END PUBLIC KEY-----\\n";

   char privateKey[]="-----BEGIN RSA PRIVATE KEY-----\\n"\\
  "MIIEowIBAAKCAQEAy8Dbv8prpJ/0kKhlGeJYozo2t60EG8L0561g13R29LvMR5hy\\n"\\
  "vGZlGJpmn65+A4xHXInJYiPuKzrKUnApeLZ+vw1HocOAZtWK0z3r26uA8kQYOKX9\\n"\\
  "Qt/DbCdvsF9wF8gRK0ptx9M6R13NvBxvVQApfc9jB9nTzphOgM4JiEYvlV8FLhg9\\n"\\
  "yZovMYd6Wwf3aoXK891VQxTr/kQYoq1Yp+68i6T4nNq7NWC+UNVjQHxNQMQMzU6l\\n"\\
  "WCX8zyg3yH88OAQkUXIXKfQ+NkvYQ1cxaMoVPpY72+eVthKzpMeyHkBn7ciumk5q\\n"\\
  "gLTEJAfWZpe4f4eFZj/Rc8Y8Jj2IS5kVPjUywQIDAQABAoIBADhg1u1Mv1hAAlX8\\n"\\
  "omz1Gn2f4AAW2aos2cM5UDCNw1SYmj+9SRIkaxjRsE/C4o9sw1oxrg1/z6kajV0e\\n"\\
  "N/t008FdlVKHXAIYWF93JMoVvIpMmT8jft6AN/y3NMpivgt2inmmEJZYNioFJKZG\\n"\\
  "X+/vKYvsVISZm2fw8NfnKvAQK55yu+GRWBZGOeS9K+LbYvOwcrjKhHz66m4bedKd\\n"\\
  "gVAix6NE5iwmjNXktSQlJMCjbtdNXg/xo1/G4kG2p/MO1HLcKfe1N5FgBiXj3Qjl\\n"\\
  "vgvjJZkh1as2KTgaPOBqZaP03738VnYg23ISyvfT/teArVGtxrmFP7939EvJFKpF\\n"\\
  "1wTxuDkCgYEA7t0DR37zt+dEJy+5vm7zSmN97VenwQJFWMiulkHGa0yU3lLasxxu\\n"\\
  "m0oUtndIjenIvSx6t3Y+agK2F3EPbb0AZ5wZ1p1IXs4vktgeQwSSBdqcM8LZFDvZ\\n"\\
  "uPboQnJoRdIkd62XnP5ekIEIBAfOp8v2wFpSfE7nNH2u4CpAXNSF9HsCgYEA2l8D\\n"\\
  "JrDE5m9Kkn+J4l+AdGfeBL1igPF3DnuPoV67BpgiaAgI4h25UJzXiDKKoa706S0D\\n"\\
  "4XB74zOLX11MaGPMIdhlG+SgeQfNoC5lE4ZWXNyESJH1SVgRGT9nBC2vtL6bxCVV\\n"\\
  "WBkTeC5D6c/QXcai6yw6OYyNNdp0uznKURe1xvMCgYBVYYcEjWqMuAvyferFGV+5\\n"\\
  "nWqr5gM+yJMFM2bEqupD/HHSLoeiMm2O8KIKvwSeRYzNohKTdZ7FwgZYxr8fGMoG\\n"\\
  "PxQ1VK9DxCvZL4tRpVaU5Rmknud9hg9DQG6xIbgIDR+f79sb8QjYWmcFGc1SyWOA\\n"\\
  "SkjlykZ2yt4xnqi3BfiD9QKBgGqLgRYXmXp1QoVIBRaWUi55nzHg1XbkWZqPXvz1\\n"\\
  "I3uMLv1jLjJlHk3euKqTPmC05HoApKwSHeA0/gOBmg404xyAYJTDcCidTg6hlF96\\n"\\
  "ZBja3xApZuxqM62F6dV4FQqzFX0WWhWp5n301N33r0qR6FumMKJzmVJ1TA8tmzEF\\n"\\
  "yINRAoGBAJqioYs8rK6eXzA8ywYLjqTLu/yQSLBn/4ta36K8DyCoLNlNxSuox+A5\\n"\\
  "w6z2vEfRVQDq4Hm4vBzjdi3QfYLNkTiTqLcvgWZ+eX44ogXtdTDO7c+GeMKWz4XX\\n"\\
  "uJSUVL5+CVjKLjZEJ6Qc2WZLl94xSwL71E41H4YciVnSCQxVc4Jw\\n"\\
  "-----END RSA PRIVATE KEY-----\\n";


  unsigned char  encrypted[4098]=;
  unsigned char decrypted[4098]=;

  int encrypted_length= public_encrypt(plainText,strlen(plainText),publicKey,encrypted);
  if(encrypted_length == -1)
  
      printLastError("Public Encrypt failed ");
      exit(0);
  
  printf("Encrypted length =%d\\n",encrypted_length);

  int decrypted_length = private_decrypt(encrypted,encrypted_length,privateKey, decrypted);
  if(decrypted_length == -1)
  
      printLastError("Private Decrypt failed ");
      exit(0);
  
  printf("Decrypted Text =%s\\n",decrypted);
  printf("Decrypted Length =%d\\n",decrypted_length);


  encrypted_length= private_encrypt(plainText,strlen(plainText),privateKey,encrypted);
  if(encrypted_length == -1)
  
      printLastError("Private Encrypt failed");
      exit(0);
  
  printf("Encrypted length =%d\\n",encrypted_length);

  decrypted_length = public_decrypt(encrypted,encrypted_length,publicKey, decrypted);
  if(decrypted_length == -1)
  
      printLastError("Public Decrypt failed");
      exit(0);
  
  printf("Decrypted Text =%s\\n",decrypted);
  printf("Decrypted Length =%d\\n",decrypted_length);

程序运行截图如下：

源码打包下载地址：

Qt/RSAEncryptionAndDecryption at master · fengfanchen/Qt · GitHub

以上是关于OpenSSL文档阅读笔记-RSA Encryption & Decryption Example with OpenSSL in C的主要内容，如果未能解决你的问题，请参考以下文章

php openssl_encrypt加密rsa加密

使用 openssl_public_encrypt 验证 RSA 签名对 .NET 签名字符串失败

openssl evp RSA 加密解密

php rsa加密已有明文和公钥只需加密

用openssl库RSA加密解密

PHP openssl_public_encrypt“密钥参数不是有效密钥”