Encoding data in message headers

Abstract

An electronic communication system is described wherein a received first email message comprises a first header field including first encoded data containing first email characterization information and when a reply or forward is made to the first email message the new second email message comprises a second header field including second encoded data containing the first email characterization information from the first encoded data and further contains second email characterization information based on a change between the first email message and the new email message. In such manner, email characterization information is persisted and accumulated across email replies and forwards (i.e. across related email messages). The encoded data may be encrypted, possibly using homomorphic encryption so that it is interpretable by one or more authorised recipients but operable by any recipient. The change between the first email and new (reply / forwarded email) may comprise a topic change, theme change, change in addressees or a change in the body of the email. A message-ID and / or In-reply-to header field may be used for the encoded data. The accumulated and persisted header data may allow tampering detection. [Figure 3B]