AES CTR Encryption IN C using OpenSSL Library - c

Question

I am trying to encrypt and decrypt a large file (100MB) using aes ctr with a 256-bit key. I downloaded this code from this http://www.gurutechnologies.net/blog/aes-ctr-encryption-in-c/. I am using Xcode to run it, but there is a problem, it give me "Read file is null" as output. I would appreciate if somebody could help me or give me a hint.
Note: I add the text file as shown in the image below:
struct ctr_state{
unsigned char ivec[AES_BLOCK_SIZE];
unsigned int num;
unsigned char ecount[AES_BLOCK_SIZE];};
FILE *readFile;
FILE *writeFile;
AES_KEY key;
int bytes_read, bytes_written;
unsigned char indata[AES_BLOCK_SIZE];
unsigned char outdata[AES_BLOCK_SIZE];
unsigned char iv[AES_BLOCK_SIZE];
struct ctr_state state;
int init_ctr(struct ctr_state *state, const unsigned char iv[16])
{
state->num = 0;
memset(state->ecount, 0, AES_BLOCK_SIZE);
/* Initialise counter in 'ivec' to 0 */
memset(state->ivec + 8, 0, 8);
/* Copy IV into 'ivec' */
memcpy(state->ivec, iv, 8);
return 0;
}
void fencrypt(char* read, char* write, const unsigned char* enc_key)
{
if(!RAND_bytes(iv, AES_BLOCK_SIZE))
{
fprintf(stderr, "Could not create random bytes.");
exit(1);
}
readFile = fopen(read,"rb"); // The b is required in windows.
writeFile = fopen(write,"wb");
if(readFile==NULL)
{
fprintf(stderr, "Read file is null.");
exit(1);
}
if(writeFile==NULL)
{
fprintf(stderr, "Write file is null.");
exit(1);
}
fwrite(iv, 1, 8, writeFile); // IV bytes 1 - 8
fwrite("\0\0\0\0\0\0\0\0", 1, 8, writeFile); // Fill the last 4 with null bytes 9 - 16
//Initializing the encryption KEY
if (AES_set_encrypt_key(enc_key, 128, &key) < 0)
{
fprintf(stderr, "Could not set encryption key.");
exit(1);
}
init_ctr(&state, iv); //Counter call
//Encrypting Blocks of 16 bytes and writing the output.txt with ciphertext
while(1)
{
bytes_read = fread(indata, 1, AES_BLOCK_SIZE, readFile);
AES_ctr128_encrypt(indata, outdata, bytes_read, &key, state.ivec, state.ecount, &state.num);
bytes_written = fwrite(outdata, 1, bytes_read, writeFile);
if (bytes_read < AES_BLOCK_SIZE)
{
break;
}
}
fclose(writeFile);
fclose(readFile);
}
void fdecrypt(char* read, char* write, const unsigned char* enc_key)
{
readFile=fopen(read,"rb"); // The b is required in windows.
writeFile=fopen(write,"wb");
if(readFile==NULL)
{
fprintf(stderr,"Read file is null.");
exit(1);
}
if(writeFile==NULL)
{
fprintf(stderr, "Write file is null.");
exit(1);
}
fread(iv, 1, AES_BLOCK_SIZE, readFile);
//Initializing the encryption KEY
if (AES_set_encrypt_key(enc_key, 128, &key) < 0)
{
fprintf(stderr, "Could not set decryption key.");
exit(1);
}
init_ctr(&state, iv);//Counter call
//Encrypting Blocks of 16 bytes and writing the output.txt with ciphertext
while(1)
{
bytes_read = fread(indata, 1, AES_BLOCK_SIZE, readFile);
//printf("%i\n", state.num);
AES_ctr128_encrypt(indata, outdata, bytes_read, &key, state.ivec, state.ecount, &state.num);
bytes_written = fwrite(outdata, 1, bytes_read, writeFile);
if (bytes_read < AES_BLOCK_SIZE)
{
break;
}
}
fclose(writeFile);
fclose(readFile);
}
int main(int argc, char *argv[])
{
fencrypt("encme.txt", "enced.enc", (unsigned const char*)"1234567812345678");
fdecrypt("enced.enc", "unenced.txt", (unsigned const char*)"1234567812345678");
getc(stdin);
return 0;
}