Why just accept me the first 2 characters in the key? C ++

Question

I have a small problem when inserting the key in a c + + project in visual studio 2010 proffessional.

When I put the key only accepts the first two keys and this can be a problem when you put a similar key that begins with the first two characters.

However when I put the key directly in hexadecimal characters validates all.

I make it clear in advance know very little I am learning c + + This is what I have done for now.

    //****************** AES decryption ********************
const int size = 32;
unsigned char aesKey[size];
char* p;

for (int i = 1; i < argc || i < size; ++i)
{
    aesKey[i] = (unsigned char)strtol(argv[2], &p, 16);
} 

unsigned char *buf;

aes256_context ctx;
aes256_init(&ctx, aesKey);

for (unsigned long i = 0; i < lSize/16; i++) {
    buf = text + (i * 16);
    aes256_decrypt_ecb(&ctx, buf);
}

aes256_done(&ctx);
//******************************************************

where I have the argument argv[2] is because that I have to use the argument 2

Any suggestions or ideas, thanks

I do not know it helped me, where argv [2] before had argv [i] but I changed because I was frozen — aleksander haugas, Jan 16 '13 at 12:25
Your code looks like C. One of the reasons to use C++ is to not have to even think about this type of problem. — juanchopanza, Jan 16 '13 at 12:25
@aleksanderhaugas You're missing the basics. How about starting with a [good book](http://stackoverflow.com/questions/388242/the-definitive-c-book-guide-and-list) first? Or at least tell us (in plain words) what you're trying to achieve. — Angew is no longer proud of SO, Jan 16 '13 at 12:27
But if I put ` for(register int i = 0; i!=size;++i) ` I feel the same — aleksander haugas, Jan 16 '13 at 12:31
@aleksanderhaugas Even more reason to learn from a book and simple examples. — Angew is no longer proud of SO, Jan 16 '13 at 12:41
yes I know more or less but are not translated into English, Any thoughts on some things to php — aleksander haugas, Jan 16 '13 at 12:43
@aleksanderhaugas - What? Why are you asking about PHP if you writting C-style C++ code? — Security Hound, Jan 16 '13 at 13:07
I was not asking about php, I say it looks a little php, sorry for my english — aleksander haugas, Jan 16 '13 at 13:18

score 1 · Answer 1 · answered Jan 16 '13 at 12:33

1

This code can have many fixes, but this is the basic I can see

//****************** AES decryption ********************
const int size = 32;
unsigned char aesKey[size];
char* p;

//check you have argv[2]
if (argc < 3)
{
    //TODO: return or handle the error as you wish...
}

//i need to start from 0 (it's a zero base index)
//argc = argument count. and this should not be here
//you have 3 arguments and this is why it read 2 chars...
for (int i = 0;i < size; ++i)
{
    aesKey[i] = (unsigned char)strtol(argv[2], &p, 16);
} 

unsigned char *buf;

aes256_context ctx;
aes256_init(&ctx, aesKey);

//I don't know where lsize is coming from but I would calculate the division out side:
unsigned long myMax = lSize/16;
for (unsigned long i = 0; i < myMax; i++) {
    buf = text + (i * 16);
    aes256_decrypt_ecb(&ctx, buf);
}

aes256_done(&ctx);
//******************************************************

answered Jan 16 '13 at 12:33

Roee Gavirel

18,955
12
67
94

I am using the class of literatecode aes256, is to decrypt the file with the hex key – aleksander haugas Jan 16 '13 at 12:41
1

I feel the same, do not know what may be happening – aleksander haugas Jan 16 '13 at 13:14
@aleksanderhaugas: Did it fix your problem ? – Roee Gavirel Jan 16 '13 at 13:45
no, it is the same as before. but thanks for your help – aleksander haugas Jan 16 '13 at 15:55

Why just accept me the first 2 characters in the key? C ++

1 Answers1