Note that if one knows both the ciphertext and the plaintext , one can easily find the shared secret , since . Therefore, a new and hence a new is generated for every message to improve security. For this reason, is also called an ephemeral key.
note that if one knows both the ciphertext and the plaintext  one can easily find the shared secret  since  therefore a new and hence a new is generated for every message to improve security for this reason is also called an ephemeral key