Thread: How to convert char array of 64 bytes to long long int

Give us an example of what DEK is when you call strtoul and what the corresponding long long int you get is, and what you expect it to be. Are you sure you want to use 0 in strtoul when you're using base 16 ("some hex value")?

Also, what are you trying to pass to AES_key_wrap because the only function I see of that name doesn't even HAVE long long int in the prototype.

You are confusing bytes with bits.


Quzah.

That's a hex number, so you have to use 16 as the final arg to your strtol() function. However, I'd guess that this number will never fit into even an unsigned long long (using strtoull), and a test confirms:

Code:

#include <stdio.h>
#include <stdlib.h>
#include <limits.h>

int main(int argc, const char *argv[]) {
	char key[]="016211c7f60824a8ec5df54737a08ad0a11b2e451160601a94ccd53555a335";
	unsigned long long x = strtoull(key, NULL, 16);
	if (x == ULLONG_MAX) puts("nope!");
	return 0;
}

nope!

So you've got something wrong. I can't find a reference to an AES_key_wrap(), but if you mean AES_wrap_key(), methinks you have misunderstood the arguments:

Code:

int AES_wrap_key(AES_KEY *key, const unsigned char *iv,
                unsigned char *out,
                const unsigned char *in, unsigned int inlen);

I've already said what the problem is: 64 bytes will not fit in 64 bits.

Currently i have a char key[64]
...

Code:

u8 DEK[64];
long long test;

'test' is not sixty four BYTES in size.


Quzah.

Originally Posted by pkumarn

AES_wrap_key() is the correct function ... if i want this into an array, then how do i assign this to AES_KEY *key.

It might help if you read the documentation for AES_wrap_key. I don't have it at hand (and never used this library either), but it should explain what you are looking for. If you don't understand it, post it here.

Originally Posted by pkumarn

where max size for storage offered is 480 bits but i need to store 512 boits

AES has a key length of at most 256 bits, so I do not understand what is up with 480 bits or 512 bits, unless you're really trying to use Rijndael rather than AES. If you have an arbitrarily long string that you want to use as a key, use a cryptographic hash like SHA-256 to obtain the key with the desired number of bits. If you already have 512 bits that were randomly generated for use as a key, just truncate it to 256 bits.

We can't do the math because you haven't told us what AES_MAXNR is.

At any rate, your key is 64 chars, each two of which represent the hex value of a byte; so it is 32 bytes or 256 bits. Your question is how do you turn this hex string into the actual 256 bits that you need. Here's the basic idea:

EDIT: Upon actually running my original code, I had to make a couple of changes. Also note that I had to add two characters to your dek string (it was only 62 chars long).

Code:

#include <stdio.h>

int main() {
    char dek[] = "016211c7f60824a8ec5df54737a08ad0a11b2e451160601a94ccd53555a335ab";
    unsigned char byte[32];
    unsigned x;
    int n;

    for (n = 0; n < 32; n++) {
        sscanf(dek+n*2, "%2x", &x);
        byte[n] = x;
    }

    printf("%s\n", dek);

    for (n = 0; n < 32; n++)
        printf("%02x", (unsigned)byte[n]);

    return 0;
}

All you really need is a hex string to binary converter. You pas in the address of the string and the address of the thing where you want the data to be put.
Internally it's just a loop converting two hexadecimal characters at once into the corresponding byte value.