What does ECDH stand for in cryptography?

ECDH stands for Elliptic Curve Diffie-Hellman, which is a key exchange protocol used to securely share cryptographic keys between two parties over a public channel. It leverages the mathematical properties of elliptic curves to offer high levels of security with smaller key sizes compared to traditional methods like the original Diffie-Hellman protocol. This efficiency makes ECDH particularly suitable for environments where computational power and bandwidth are limited.

The security of ECDH is derived from the difficulty of the elliptic curve discrete logarithm problem, which ensures that even if an attacker observes the exchanged values, they cannot feasibly derive the shared secret without knowledge of the private keys.

In a standard ECDH exchange, both parties generate their own private keys and corresponding public keys. They then exchange public keys and compute the shared secret independently, which will be identical for both parties, allowing them to use it for encryption or authentication purpose.

Other options like Elliptic Curve Data Hash, Elliptical Compression Data Hash, and Elliptic Coordination Dissolution Hash do not align with established cryptographic terminology related to key exchange methods, and thus reinforce why the correct choice is indeed the one that pertains specifically to the key exchange framework using elliptic curves.