1) create similar decrypt_file.cpp program that decrypts given file using 
   given password

2) create random session key and save it as plaintext to file
   (using CryptGenKey, CryptExportKey (with dwBlobType = PLAINTEXTKEYBLOB))

3) create new context and generate assymetric keys for signing and key exchange
   (using CryptAcquireContext (with dwFlags = CRYPT_NEWKEYSET))

4) with generated private key for key exchange encrypt session key and save it
   to file
   (using CryptGenKey for creating session key, CryptGetUserKey
   (with dwKeySpec = AT_KEYEXCHANGE) and CryptExportKey
   (with dwBlobType = SIMPLEBLOB)