OpenSSL Encryption in Debug and Release

Question

I have the following code (modified ik and iv, of course):

#include "openssl/evp.h"

#include <iostream>
#include <sstream>
#include <string>

using std::cout;
using std::endl;
using std::string;
using std::ostringstream;

void Encryption(bool encrypt, const string &in, string &out)
{
    int ik[17] = {  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15, 16 };
    int iv[17] = { 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32 };
    ik[16] = iv[16] = '\0';
    unsigned char ckey[17], ivec[17];
    for (int i = 0; i < 16; ++i)
    {
        ckey[i] = ik[i];
        ivec[i] = iv[i];
    }
    EVP_CIPHER_CTX *ctx = EVP_CIPHER_CTX_new();
    EVP_CipherInit(ctx, EVP_aes_256_cbc(), ckey, ivec, encrypt);
    unsigned blocksize = EVP_CIPHER_CTX_block_size(ctx);

    int out_len;
    int n = in.length() + blocksize;
    unsigned char *cipher_buf = new unsigned char[n];
    for (int i = 0; i < n; ++i)
        cipher_buf[i] = ' ';
    EVP_CipherUpdate(ctx, cipher_buf, &out_len,
                     (const unsigned char*)in.c_str(), in.length());
    std::ostringstream ss;
    ss.write((char*)cipher_buf, out_len);
    EVP_CipherFinal(ctx, cipher_buf, &out_len);
    ss.write((char*)cipher_buf, out_len);
    delete cipher_buf;
    out = ss.str();
    EVP_CIPHER_CTX_free(ctx);
}    

int main()
{
    string out;
    string in = "TEST";
    string back;
    Encryption(true, in, out);
    cout << "---------------" << endl;
    Encryption(false, out, back);
    cout << "TEST > " << out << " > " << back << endl;
    return 0;
}

Basically, this code encrypts a string, decrypts it and then prints out the result from both steps.

If I run this code in Debug, it works just fine, outputting TEST > *gibberish A* > TEST. If I run it on Release, however, it fails, printing only TEST > *gibberish B (not A)* >, because back remains empty. Seeing this question and another one I can't find now, I made a copy of my Release configuration and went changing one parameter at a time to the equivalent value in the Debug configuration. When I changed Configuration Properties > C/C++ > Code Generation > Basic Runtime Checks from Default to Both (/RTC1, equiv. to /RTCsu) (/RTC1), this new Release configuration worked, printing exactly the same values as in the Debug configuration. Obviously, by then I'd already changed many other parameters, but it was only when I changed the value of /RTC that any change was clear in the execution.

I also noticed something else. If I removed the cout << "---------------" << endl; line in main(), the default Release configuration also works, printing TEST > *gibberish C* > TEST. The encryption gibberish is different to both the Debug result and the Release with the cout line. Also, if I place that cout call anywhere other than between my Encryption calls, it works.

So I have two questions I believe may be interrelated:

• Why does the value of /RTC affect the encryption result? Given that /RTC should be disabled in Release builds, is it possible to generate equivalent encrypted data (aka gibberish) in both Debug and Release, so as to make them interchangeable, without losing /RTC in Debug?
  • Why does the use of cout in between my Encryption() calls modify the result in Release mode and only in Release mode?

And, should it be worth mentioning, everything is built with the static runtime library (/MT[d]).