AES Encryption and Decryption using OpenSSL in CPP

#include <iostream>

using namespace std;

#include <string>

#include <openssl/evp.h>

#include <openssl/objects.h>

/*

* Define your own KEY for Encryption and Decryption of Data

*/

static const unsigned char DCPKey[] = {0xC2,0x3B,0x73,0xCC,0xF0,0x2E,0x4D,0xBA,

0xAF,0xDE,0x73,0x54,0x90,0xCD,0xAB,0xEF,

0xA1,0xC8,0x02,0x3A,0xFC,0x40,0xA8,0xB4,

0xB4,0x70,0x0A,0x3E,0xCA,0xA7,0x04,0xE3};

string AES_Decrypt(string ENCstr)

{

EVP_CIPHER_CTX *ctx = EVP_CIPHER_CTX_new();

EVP_CIPHER_CTX_init(ctx);

EVP_CIPHER_CTX_set_padding(ctx, 0);

int ret = EVP_DecryptInit_ex(ctx, EVP_aes_256_cfb(), NULL, DCPKey, NULL);

    unsigned char* result = new unsigned char[ENCstr.length()]; // Make a big enough space

    int *len1 = new int();;

    ret = EVP_DecryptUpdate(ctx, result, len1, (const unsigned char*)ENCstr.data(), ENCstr.length());

    int *len2 = new int();

    ret = EVP_DecryptFinal_ex(ctx, result+ *len1, len2); 

    ret = EVP_CIPHER_CTX_cleanup(ctx);

    string res((char*)result, *len1+ *len2);

    delete[] result;

delete len1;

delete len2;

EVP_CIPHER_CTX_free(ctx);

    return res;

}

string AES_Encrypt(const std::string source)

{

EVP_CIPHER_CTX *ctx = EVP_CIPHER_CTX_new();

EVP_CIPHER_CTX_init(ctx);

    int ret = EVP_EncryptInit_ex(ctx, EVP_aes_256_cfb(), NULL, DCPKey, NULL);

EVP_CIPHER_CTX_set_padding(ctx, 0);

    unsigned char* result = new unsigned char[source.length() + 64]; // Make a big enough space

    int *len1 = new int();

    ret = EVP_EncryptUpdate(ctx, result, len1, (const unsigned char*)source.data(), source.length());

    int *len2 = new int();

    ret = EVP_EncryptFinal_ex(ctx, result+*len1, len2); 

    ret = EVP_CIPHER_CTX_cleanup(ctx);

    std::string res((char*)result, *len1 + *len2);

    delete[] result;

delete len1;

delete len2;

EVP_CIPHER_CTX_free(ctx);

    return res;

}

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

{

cout << "AES Encryption Decryption in progress.. Keep Waiting" << endl;

char buf[1024*100];

    FILE* ifp = fopen("input.txt", "rb");

  int bytes = fread(buf, 1, 1024*100, ifp);

  fclose(ifp);

std::string source(buf, bytes); // binary data

string Encrypted_Data = AES_Encrypt (source);

//cout << "Encrypted Data: " << Encrypted_Data << endl;

FILE* efp =  fopen("encrypted.txt", "wb");

  fwrite(Encrypted_Data.data(), 1, Encrypted_Data.length(), efp);

fclose(efp);

string Decrypted_Data = AES_Decrypt (Encrypted_Data);

FILE* dfp =  fopen("output.txt", "wb");

  fwrite(Decrypted_Data.data(), 1, Decrypted_Data.length(), dfp);

fclose(dfp);

return 0;

}

Compilation:

g++ -o aes AES.cpp -lssl -lcrypto

./aes

input.txt -- Source data to encrypt

encrypted.txt -- Encrypted Source Data after processing

output.txt -- Decrypted Data

sample contents of input.txt

[openssl]

CPP program to encrypt data using openSSL library

Also decrypt the same using openSSL library

Using builtin cipher Algorithm present in OpenSSL

Code can be accessed from GitHub