Can you help me get my head around openssl public key encryption with rsa.h in c++?

Question

I am trying to get my head around public key encryption using the openssl implementation of rsa in C++. Can you help? So far these are my thoughts (please do correct if nece

Answer 1

Actually, no problem, I have just read that basically, the RSA object is a structure that contains both public and private fields. One can extract the public field data and only send that to Bob.

I.e. basically, to extract the public fields from rsa and store each in two different buffers (which are char arrays and can then be sent to Bob), you do:

sprintf(keyBufferA,"%s\r\n",BN_bn2hex(rsa->n));
sprintf(keyBufferB,"%s\r\n",BN_bn2hex(rsa->e));

And then Bob, on the receiving end, reconstructs as follows:

rsa = RSA_new();
BN_hex2bn(&rsa->n, keybufA);
BN_hex2bn(&rsa->e, keybufB);

Bob can then use rsa* to publicly encrypt the symmetric cypher key which can then be sent to Alice. Alice can then decrypt with the private key

Ben.