Encryption using openssl lib

[芦翔]

Dear all,

 

I would like to encrypt the transmitting data on the server side before the 
data is send to a socket. And then, decrypt the data from the socket on the 
client side. I am using the following code, which is from Internet.

 

#include "encryption.h"
byte_t* BufferEncryption(const byte_t* apBuffer, size_t aNumBytes)
{
 int ret;
 EVP_CIPHER_CTX ctx;
 const EVP_CIPHER* cipher;
 byte_t key[24], iv[8], out[500];
 int i, len, inl, outl, total = 0;

 for (i = 0; i < 24; i ++)
 {
  memset(&key[i], i, 1);
 }
 for (i = 0; i < 8; i ++)
 {
  memset(&iv[i], i, 1);
 }
 EVP_CIPHER_CTX_init(&ctx);
 cipher = EVP_des_ede3_ofb();
 //cipher = EVP_des_ede3_cbc();
 ret = EVP_EncryptInit_ex(&ctx, cipher, NULL, key, iv);
 if (ret != 1)
 {
  printf("EVP_EncryptInit_ex err!\n");
  return (byte_t*)"error";
 }
 inl = 50;
 len = 0;
 
 int j = aNumBytes / inl;
 
 for (int k = 0; k < j; k ++)
 {
  EVP_EncryptUpdate(&ctx, out + len, &outl, apBuffer + inl, inl);
  len += outl;
 }
 EVP_EncryptFinal_ex(&ctx, out+len, &outl);
 len += outl;

 return (byte_t*)out;
}

 

apBuffer is the pointer to the buffer storage the unencrypted data. aNumBytes 
is the length of the apBuffer.

There are two questions.

(1)The apBuffer is always less than inl=50. Should I use EVP_EncryptUpdate for 
one time to encrypt my data, or should I use EVP_encryptFinal_ex directly?

(2)I don't think the code works. The execution is terminated without encryption 
on 

            ret = EVP_EncryptInit_ex(&ctx, cipher, NULL, key, iv); 

I don't know why.

 

Could anyone please help me to answer the two questions? Any help will be 
really appreciated. Thank you so much.

 

Best Regards,

Xiang

                                          
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