How to convert OpenSSL SHA-512 hash to GMP number to use in RSA encryption method

Question

SHA1(data, length, hash);
unsigned char *labelPtr;

labelPtr = hash;
mpz_set_str (encrypted, labelPtr, 16);
gmp_printf("hashed= %Zd\n", encrypted);

encrypted equals 0? I need to get an integer from this hash so that I can perform RSA encryption. I see the hash when I debug, but cannot seem to turn this into an int. It is SHA-512 so 512 bits? Weird characters come out of printf("%s",hash); atoi gives 0 too, do I have to break up the hash by character? That would work I think.

yes sha1 is smaller but 512 is more secure and gmp should be able to handle it — csestony, Oct 07 '12 at 19:38
That's not the point, you mention `SHA-512` but your program is using a `SHA1` function. — ouah, Oct 07 '12 at 19:40
no this is open ssh so you can define sha 512 unsigned char hash[SHA_DIGEST_LENGTH]; — csestony, Oct 07 '12 at 19:42
sha_digest_length in open ssl defines sha 1 which is 160 bit or 256 or 512 i defined it as 512 — csestony, Oct 07 '12 at 19:43

score 1 · Accepted Answer · answered Oct 07 '12 at 19:42

1

mpz_set_str second parameter must be a string.

The hash argument you pass to SHA1 function is probably not a string. Convert it to a string format before passing it to the mpz_set_str function.

answered Oct 07 '12 at 19:42

ouah

142,963
15
272
331

\355\020\ is the value in the hash after – csestony Oct 07 '12 at 19:47
if i use print f wierd characters come out printf("%s",hash); so im sure its a string... just very wierd atoi gives 0 too, do i have to break up the hash by character because that would work i think – csestony Oct 07 '12 at 19:48
@Thefirstkilla `mpz_set_str (encrypted, labelPtr, 16)` requires you to have a string and basis 16 to be used. Your string should be printable: you have to convert your array to a string with basis 16 values. You can use `sprintf` to do that. – ouah Oct 07 '12 at 19:57

How to convert OpenSSL SHA-512 hash to GMP number to use in RSA encryption method

1 Answers1

Linked