MBEDTLS_ECDH_H macro

\file ecdh.h This file contains ECDH definitions and functions. The Elliptic Curve Diffie-Hellman (ECDH) protocol is an anonymous key agreement protocol allowing two parties to establish a shared secret over an insecure channel. Each party must have an elliptic-curve public–private key pair. For more information, see NIST SP 800-56A Rev. 2: Recommendation for Pair-Wise Key Establishment Schemes Using Discrete Logarithm Cryptography.