Initialize Public Key From Modulus & Exponent using OpenSSL

Question

Trying to generate an RSA Public Key given an APIs modulus and exponent. I\'m using OpenSSL on iOS 4.2.

Generating the public key manually is an option (see below) h

Answer 1

To do this make sure you have the OpenSSL library linked (instructions here http://code.google.com/p/ios-static-libraries/)

Once linked you'll have access to several BIGNUM converters. I turned the modulus into hex using the BN_hex2bn method saving the hex string into 'exponent'

Then create the BIGNUM struct and encrypt using RSA_public_encrypt

RSA *rsa = NULL;

rsa->n = BN_new();
BN_copy(rsa->n,modulus);   
rsa->e = BN_new();
BN_copy(rsa->e,exponent);     
rsa->iqmp=NULL;
rsa->d=NULL;
rsa->p=NULL;
rsa->q=NULL;

Good Luck!