Validating diffie hellman public private keys

Posted by / 23-Nov-2017 06:04

Elliptic curve Diffie–Hellman (ECDH) is an anonymous key agreement protocol that allows two parties, each having an elliptic curve public–private key pair, to establish a shared secret over an insecure channel.

This shared secret may be directly used as a key, or to derive another key.

The key, or the derived key, can then be used to encrypt subsequent communications using a symmetric key cipher.

It is a variant of the Diffie–Hellman protocol using elliptic curve cryptography.

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There are several ways to provide these additional measures (e.g.

The method includes obtaining the public key, and verifying, by the computing device, that the obtained public key is a point on an elliptic curve defined over a finite field, the... In key transport protocols a Correspondent A may inadvertently send its symmetric key to the wrong party.

This worries me that people are using this code as a template for building real ECDHE key agreement, when it was only intended as a guide to the Java API.

There are a of details in safe construction of such a protocol.

The following example will illustrate how a key establishment is made.

Suppose Alice wants to establish a shared key with Bob, but the only channel available for them may be eavesdropped by a third party. The only information about her private key that Alice initially exposes is her public key.

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Update 2 (17th May, 2017): I’ve written some notes on correctly validating ECDH public keys.