Key Exchange (KX) - A Next Generation Protocol to Synchronise PGP Keyservers
In the Internet, securing email has always been an important issue. Various standards and products have been created. One of the most successful standards is OpenPGP , which uses public key cryptography (RSA  and others) and is implemented in systems like Pretty Good Privacy , GNU Privacy Guard , Hushmail  and others. A well-known difficulty with the use of public key cryptographic systems is the verification and distribution of the public keys. OpenPGP solves the problem of verifying the authenticity of a public key by having users certify each others keys, building a "Web of Trust"  by bundling these key certificates with each users public key. Therefore, adding a new public key and updating an existing public key (or replacing it by a new version) are the two most important operations of any PGP public key repository.
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