It’s easy to generate a RSA keypair in PHP, just like this:

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<?php
// Create the keypair
$res=openssl_pkey_new();

// Get private key
openssl_pkey_export($res, $privkey);

// Get public key
$pubkey=openssl_pkey_get_details($res);
$pubkey=$pubkey["key"];
?>

But when it comes to C, it’s not that simple.

You might want to use RSA_generate_key and then PEM_write_RSAPublicKey, but in fact, the output format of PHP’s openssl_pkey_get_details is not a RSA public key.

If you want to get the same result in C, you have to convert your RSA keypair into EVP keypair.

Here’s my sample script:

You can test it by folloing commands: gcc -o key key.c -lssl && ./key