4/23/2021 0 Comments Diffie Hellman Key Exchange
Revoked certificates are usually put in certificate revocation lists which any certificate can be matched against.Please help improve this article by adding citations to reliable sources.Find sources: Key exchange news newspapers books scholar JSTOR ( November 2014 ) ( Learn how and when to remove this template message ).After obtaining an authentic copy of each others public keys, Alice and Bob can compute a shared secret offline.
The shared secret can be used, for instance, as the key for a symmetric cipher. The nature of the equipping they require depends on the encryption technique they might use. ![]() If the cipher is a symmetric key cipher, both will need a copy of the same key. ![]() Historically, before the invention of public-key cryptography (asymmetrical cryptography), symmetric-key cryptography utilized a single key to encrypt and decrypt messages. For two parties to communicate confidentially, they must first exchange the secret key so that each party is able to encrypt messages before sending, and decrypt received ones. If two parties cannot establish a secure initial key exchange, they wont be able to communicate securely without the risk of messages being intercepted and decrypted by a third party who acquired the key during the initial key exchange. It depends on the selected cryptographic algorithm which keypublic or privateis used for encrypting messages, and which for decrypting. For example, in RSA, the private key is used for decrypting messages, while in the Digital Signature Algorithm (DSA), the private key is used for encrypting them. The public key can be sent over non-secure channels or shared in public; the private key is only available to its owner. One party exchanges the keys to another party where they can then encrypt messages using the key and send back the cipher text. Only the decryption keyin this case, its the private keycan decrypt that message. At no time during the Diffie-Hellman key exchange is any sensitive information at risk of compromise, as opposed to symmetrical key exchange. Because it is possible to spoof anothers identity in any of several ways, this is not a trivial or easily solved problem, particularly when the two users involved have never met and know nothing about each other. The protocol enables users to securely exchange secret keys even if an opponent is monitoring that communication channel. The DH key exchange protocol, however, does not by itself address authentication (i.e. Authentication is crucial when an opponent can both monitor and alter messages within the communication channel (AKA man-in-the-middle or MITM attacks) and was addressed in the fourth section of the paper. In their most usual implementation, each user applies to a certificate authority (CA), trusted by all parties, for a digital certificate which serves for other users as a non-tamperable authentication of identity. The infrastructure is safe, unless the CA itself is compromised. In case it is, though, many PKIs provide a way to revoke certificates so other users will not trust them.
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