DiffieHellmani

DiffieHellmani is not a standard term in cryptography. It appears to be a misspelling or playful variant of Diffie-Hellman. The widely recognized concept is Diffie-Hellman key exchange, a foundational protocol for establishing a shared secret over an insecure channel without prior shared keys.

Diffie-Hellman was introduced in 1976 by Whitfield Diffie and Martin Hellman. It enables two parties to agree on a symmetric key that can be used for subsequent encrypted communication. The protocol relies on the difficulty of the discrete logarithm problem and does not itself provide authentication. By design, it allows a participant to contribute a private value and a public value derived from that private value, exchange the public values, and then compute a common secret from the received value and their own private value.

In its classic form, the two parties agree on public parameters, typically a large prime p and a generator g. Each party chooses a private key, computes a public value as g raised to their private key modulo p, and exchanges the public values. Each party then raises the received public value to their own private key, producing the shared secret, which should be equal for both sides. This shared secret can seed symmetric encryption keys.

Security relies on the hardness of the discrete logarithm problem and on using ephemeral parameters to achieve forward secrecy. Because Diffie-Hellman provides no authentication, it is vulnerable to man-in-the-middle attacks unless combined with an authentication mechanism, such as digital signatures or a public key infrastructure. Variants include Elliptic Curve Diffie-Hellman (ECDH), which offers comparable security with smaller key sizes and improved performance. Diffie-Hellman remains a core component of modern secure protocols, notably Transport Layer Security (TLS).