As you already noted, there are two ways to exchange symmetric session keys: through key encipherment or through key agreement (which is based on Diffie-Hellman algorithm). First, they need to be agree upon a modulus, which is a prime p, and a base g for computing the public key and symmetric key. The message exchange using symmetric key cryptography involves the following steps- Before starting the communication, sender and receiver shares the secret key. Since the key has been transferred using a secure channel, a symmetric key can be used for data exchange. Rather than create a symmetric key cipher and find a way to securely exchange keys, then figure out a way to use out-of-band verification to ensure there wasn't a … The provided information is an extension of Managing AES, DES, and HMAC cryptographic keys.Refer to this topic for additional information on symmetric … The Diffie-Hellman algorithm helps with this. You have to figure out a way to get the private key to all systems. Symmetric-key Authenticated Key Exchange (SAKE) with Perfect Forward Secrecy Gildas Avoine 1;2, S ebastien Canard 3, and Lo c Ferreira 1 Univ Rennes, INSA Rennes, CNRS, IRISA, France 2 Institut Universitaire de France gildas.avoine@irisa.fr 3 Orange Labs, Applied Crypto Group, Caen, France fsebastien.canard,loic.ferreirag@orange.com Assume Alice and Bob would like to exchange a secret symmetric key for their secure communications. For the symmetric key, you can approach this problem as a complete graph with order 1000. At sender side, sender encrypts the message using his copy of the key. Although symmetric key algorithms are fast and secure, key exchange is always a problem. Here is a Diffie-Hellman key example. This secret key is shared through some external means. Then each vertex would have degree 999 and, applying the Handshaking lemma, the number of edges would be: $(1000 \times 999)/2 = 499500$ Although slower than symmetric key encryption, this method ensures the key cannot accessed by a 3rd party while being transferred. Symmetric Easy to follow VPN describes how the symmetric trying to establish a tutorial. In particular, they can provide perfect forward secrecy, as illustrated by key exchange protocols based on the Diffie-Hellman scheme. The Diffie-Hellman algorithm is mostly used for key exchange. Using asymmetric techniques in the key exchange process is more secure. With the vertexes representing people and the edges representing the symmetric keys. Exchanging symmetric keys in public channels (like on the internet) otherwise is an issue because the key is vulnerable. Key exchange protocols in the asymmetric-key setting are known to provide stronger security properties than protocols in symmetric-key cryptography. 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