linux下使用openssl对socket通信加密

Openssl AES加密（字符串加密）

1.首先安装openssl和相关库(Ubuntu)
apt-get install openssl libssl-dev
2.编写相关加密解密代码

aes_options.h

     ifndef _ASE_H_ 
     #define _ASE_H_
     int encrypt(char *input_string, char **encrypt_string);
     void decrypt(char *encrypt_string, char **decrypt_string, int len);
     endif

aes_options.c

#include <stdio.h>
#include <openssl/aes.h>
#include <stdlib.h>
#include <string.h>


//这个函数将输入字符串加密
int encrypt(char *input_string, char **encrypt_string)
{
    AES_KEY aes;
    unsigned char key[AES_BLOCK_SIZE];        // AES_BLOCK_SIZE = 16
    unsigned char iv[AES_BLOCK_SIZE];        // init vector
    unsigned int len;        // encrypt length (in multiple of AES_BLOCK_SIZE)
    unsigned int i;

    // set the encryption length
    len = 0;
    if ((strlen(input_string) + 1) % AES_BLOCK_SIZE == 0) 
    {
        len = strlen(input_string) + 1;
    } 
    else 
    {
        len = ((strlen(input_string) + 1) / AES_BLOCK_SIZE + 1) * AES_BLOCK_SIZE;
    }

    // Generate AES 128-bit key
    for (i=0; i<16; ++i) {
        key[i] = 32 + i;
    }

    // Set encryption key
    for (i=0; i<AES_BLOCK_SIZE; ++i) {
        iv[i] = 0;
    }
    if (AES_set_encrypt_key(key, 128, &aes) < 0) {
        fprintf(stderr, "Unable to set encryption key in AES\n");
        exit(0);
    }

    // alloc encrypt_string
    *encrypt_string = (unsigned char*)calloc(len, sizeof(unsigned char));    
    if (*encrypt_string == NULL) {
        fprintf(stderr, "Unable to allocate memory for encrypt_string\n");
        exit(-1);
    }

    // encrypt (iv will change)
    AES_cbc_encrypt(input_string, *encrypt_string, len, &aes, iv, AES_ENCRYPT);
    return len;
}

//这个函数将字符串解密
void decrypt(char *encrypt_string, char **decrypt_string,int len)
{
    unsigned char key[AES_BLOCK_SIZE];        // AES_BLOCK_SIZE = 16
    unsigned char iv[AES_BLOCK_SIZE];        // init vector
    AES_KEY aes;
    int i;
    // Generate AES 128-bit key

    for (i=0; i<16; ++i) {
        key[i] = 32 + i;
    }

    // alloc decrypt_string
    *decrypt_string = (unsigned char*)calloc(len, sizeof(unsigned char));
    if (*decrypt_string == NULL) {
        fprintf(stderr, "Unable to allocate memory for decrypt_string\n");
        exit(-1);
    }

    // Set decryption key
    for (i=0; i<AES_BLOCK_SIZE; ++i) {
        iv[i] = 0;
    }
    if (AES_set_decrypt_key(key, 128, &aes) < 0) {
        fprintf(stderr, "Unable to set decryption key in AES\n");
        exit(-1);
    }

    // decrypt
    AES_cbc_encrypt(encrypt_string, *decrypt_string, len, &aes, iv, 
            AES_DECRYPT);
}

最后很重要的一点
如果客户端用到加密函数，编译的格式：gcc client.c aes_options.c -o client.c -lpthread -lcrypto

-lcryto 是openssl加密必须要加上的动态库
原文链接