The first public public key memorandum of understanding [1] that meets the above criteria was the Diffie-Hellman key exchange, in which two parties jointly exposed a generator to random numbers, so that an earpiece cannot easily determine what the resulting value is used to create a common key. Key exchange protocols are designed to resolve the problem of a secret key between two or more parties, without an unauthorized party intercepting, deducing or otherwise receiving it. Key exchange algorithm, often called key exchange protocol, is any method in cryptography that allows the exchange of secret cryptographic keys between two parties, usually via a public communication channel. To avoid the use of additional off-band authentication factors, Davies and Price proposed the use of Ron Rivest and Adi Shamir`s Interlock protocol, which has come under subsequent attack and refinement. Hybrid systems use cryptography with a public key to exchange secret keys that are then used in a cryptography system with symmetrical keys. Most practical applications of cryptography use a combination of cryptographic functions to deploy a global system that provides the four desirable functions of secure communication (confidentiality, integrity, authentication and non-contestable). Key exchange protocols allow two or more parties to set up a shared encryption key that allows them to encrypt or sign data they want to exchange. Key exchange protocols typically use cryptography to achieve this goal. To achieve this goal, different cryptographic techniques can be used. A large number of cryptographic authentication schemes and protocols have been designed to provide authenticated key agreements to prevent man-in-the-middle and related attacks. These methods generally mathematically link the agreed key to other agreed data, such as.

B: A naïve example of a key exchange protocol is that a party writes a secret key, places it in an unmanipulated envelope and sends it to the recipient. If the envelope is intact, the secret key can be used by both parties to decrypt the messages. Internet Key Exchange (IKE) is the protocol used to set up a secure and authenticated communication channel between two parties. IKE uses PKI X.509 certificates for Diffie Hellman authentication and key exchange protocol to create a secret key for joint meetings. A widespread mechanism for repelling these attacks is the use of digitally signed keys, which must be secured for integrity: if Bob`s key is signed by a trusted third party guarantor of his identity, Alice can have great confidence that a signed key she receives is not an attempt to intercept Eve. If Alice and Bob have an infrastructure with public keys, they can digitally sign a Diffie Hellman key or exchange a Diffie Hellman public key. These signed keys, sometimes signed by a certification body, are one of the primary mechanisms used for secure web data traffic (including DEE, SSL or Transport Layer Security protocols). Other specific examples are: MQV, YAK and the ISAKMP component of the IPsec protocol suite for securing internet protocol communications. However, these systems require care to support consistency between identity information and public keys by certification bodies in order to function properly.