In my previous post I explained that we needed to encrypt a communication messages between Windows C++/VCL client and PHP based web service. We cannot use SSL and decided to use RSA encryption with the help of low-level functions provided by CryptoAPI at the client side and OpenSSL PHP extension at the server.
We also faced and resolved the key incompatibility problem. See my post about this.
In this post I will describe implementation or RSA encryption/decryption and digital signing.