https://www.feistyduck.com/library/openssl-cookbook/online/

Windows Complied OpenSSL binary installer

https://slproweb.com/products/Win32OpenSSL.html 

Generate a RSA private / public key pair:

genrsa -out rsa_private_key.pem 1024
rsa -in rsa_private_key.pem -pubout -out rsa_public_key.pem