Simplify the following text for a Grade 14 native English-speaking person.
Original: The Station-to-Station ( STS ) protocol is a cryptographic key agreement scheme based on the classic Diffie-Hellman key exchange that provides mutual key and entity ( party ) authentication .
Simplified: The Station-to-Station ( STS ) protocol is a cryptographic key agreement scheme based on classic Diffie-Hellman that provides mutual key and entity authentication .