Diffie – Hellman key exchange ( D – H ) is a specific method of exchanging cryptographic keys.

The Diffie – Hellman key exchange method allows two parties that have no prior knowledge of each other to jointly establish a shared secret key over an insecure communications channel.

In 2002, Hellman suggested the algorithm be called Diffie – Hellman – Merkle key exchange in recognition of Ralph Merkle's contribution to the invention of public-key cryptography ( Hellman, 2002 ).

Although Diffie – Hellman key agreement itself is an anonymous ( non-authenticated ) key-agreement protocol, it provides the basis for a variety of authenticated protocols, and is used to provide perfect forward secrecy in Transport Layer Security's ephemeral modes ( referred to as EDH or DHE depending on the cipher suite ).

The system ... has since become known as Diffie – Hellman key exchange.

While that system was first described in a paper by Diffie and me, it is a public key distribution system, a concept developed by Merkle, and hence should be called ' Diffie – Hellman – Merkle key exchange ' if names are to be associated with it.

Diffie – Hellman establishes a shared secret that can be used for secret communications by exchanging data over a public network.

* the elliptic curve Diffie – Hellman ( ECDH ) key agreement scheme is based on the Diffie – Hellman scheme,

* Curve25519: A state-of-the-art Diffie – Hellman function by Dan Bernstein

Several public-key cryptography algorithms, such as RSA and the Diffie – Hellman key exchange, are based on large prime numbers ( for example 512 bit primes are frequently used for RSA and 1024 bit primes are typical for Diffie – Hellman .).

The Diffie – Hellman key exchange relies on the fact that there are efficient algorithms for modular exponentiation, while the reverse operation the discrete logarithm is thought to be a hard problem.

In the Diffie – Hellman key exchange scheme, each party generates a public / private key pair and distributes the public key ... After obtaining an authentic copy of each others ' public keys, Alice and Bob can compute a shared secret offline.

These researchers independently developed Diffie – Hellman key exchange, and a special case of RSA.

The scheme was first published by Whitfield Diffie and Martin Hellman in 1976, although it was later alleged that it had been separately invented a few years earlier within GCHQ, the British signals intelligence agency, by Malcolm J. Williamson but was kept classified.

, now expired, describes the algorithm and credits Hellman, Diffie, and Merkle as inventors.

There was some criticism from various parties, including from public-key cryptography pioneers Martin Hellman and Whitfield Diffie, citing a shortened key length and the mysterious " S-boxes " as evidence of improper interference from the NSA.

This method of key exchange, which uses exponentiation in a finite field, came to be known as Diffie – Hellman key exchange.

* Diffie – Hellman key exchange protocol

It was the need to synchronize the scramblers that suggested to James H. Ellis the idea for non-secret encryption which ultimately led to the invention of both the RSA encryption algorithm and Diffie-Hellman key exchange well before either was reinvented publicly by Rivest, Shamir, and Adleman, or by Diffie and Hellman.

In cryptography, the ElGamal encryption system is an asymmetric key encryption algorithm for public-key cryptography which is based on the Diffie – Hellman key exchange.

The public disclosure of both secure key exchange and asymmetric key algorithms in 1976 by Diffie, Hellman, Rivest, Shamir, and Adleman changed secure communications entirely.

IKE uses X. 509 certificates for authentication which are either pre-shared or distributed using DNS ( preferably with DNSSEC ), and a Diffie – Hellman key exchange to set up a shared session secret from which cryptographic keys are derived.

IKE phase 1's purpose is to establish a secure authenticated communication channel by using the Diffie – Hellman key exchange algorithm to generate a shared secret key to encrypt further IKE communications.

Diffie – Hellman key exchange •

# REDIRECT Diffie – Hellman key exchange

# REDIRECT Diffie – Hellman key exchange

It has become known as Diffie – Hellman key exchange.

It has become known as Diffie – Hellman key exchange.

If the computational Diffie – Hellman assumption holds in the underlying cyclic group, then the encryption function is one-way.

Semantic security is not implied by the computational Diffie – Hellman assumption alone.

See decisional Diffie – Hellman assumption for a discussion of groups where the assumption is believed to hold.

It put an end to the War of the Castilian Succession, which ended with a victory of the Catholic Monarchs on land < ref name =" Bailey W. Diffie ">< sub >< big >↓</ big ></ sub > Bailey W. Diffie and George D. Winius “ In a war in which the Castilians were victorious on land and the Portuguese at sea, …” in Foundations of the Portuguese empire 1415-1580, volume I, University of Minnesota Press, 1985, p. 152 .</ ref > and a Portuguese victory on the sea .< ref name =" Historian Malyn Newitt ">< sub >< big >↓</ big ></ sub > Historian Malyn Newitt: “ All things considered, it is not surprising that the Portuguese emerged victorious from this first maritime colonial war.

Martin Edward Hellman ( born October 2, 1945 ) is an American cryptologist, and is best known for his invention of public key cryptography in cooperation with Whitfield Diffie and Ralph Merkle.

Bailey Whitfield ' Whit ' Diffie ( born June 5, 1944 ) is an American cryptographer and one of the pioneers of public-key cryptography.

After a long career at Sun Microsystems, where he became a Sun Fellow, Diffie is currently serving as the Vice President for Information Security and Cryptography at the Internet Corporation for Assigned Names and Numbers ( ICANN ) and a visiting scholar at the Freeman Spogli Institute's Center for International Security and Cooperation at Stanford University.

In 1976, Whitfield Diffie and Martin Hellman published a cryptographic protocol, ( Diffie – Hellman key exchange ), which allows users to establish ' secure channels ' on which to exchange keys, even if an Opponent is monitoring that communication channel.

This protocol allows two parties to generate a key only known to them, under the assumption that a certain mathematical problem ( e. g., the Diffie – Hellman problem in their proposal ) is computationally infeasible ( i. e., very very hard ) to solve, and that the two parties have access to an authentic channel.

He and Diffie were the most prominent critics of the short key size of the Data Encryption Standard in 1975.

Its security is based on the computational intractability ( widely assumed, but not proved ) of the decisional Diffie – Hellman assumption.

However, the discrete logarithm problem can be used as the basis for a trapdoor when the related problems called the computational Diffie – Hellman problem ( CDH ) and / or its decisional variant are used.

The external Diffie – Hellman ( XDH ) assumption is a mathematic assumption used in elliptic curve cryptography.

PFS was originally introduced by Diffie, van Oorschot, and Wiener and used to describe a property of the Station-to-Station protocol ( STS ), where the long-term secrets are private keys.