Editing Public-key cryptography (section)

===Unencrypted metadata===
Most of the available public-key encryption software does not conceal [[metadata]] in the message header, which might include the identities of the sender and recipient, the sending date, subject field, and the software they use etc.  Rather, only the body of the message is concealed and can only be decrypted with the private key of the intended recipient.  This means that a third party could construct quite a detailed model of participants in a communication network, along with the subjects being discussed, even if the message body itself is hidden.

However, there has been a recent demonstration of messaging with encrypted headers, which obscures the identities of the sender and recipient, and significantly reduces the available metadata to a third party.<ref>
{{cite arXiv
 |last1=Bjorgvinsdottir |first1=Hanna
 |last2=Bentley |first2=Phil
 |date=2021-06-24
 |title=Warp2: A Method of Email and Messaging with Encrypted Addressing and Headers
 |class=cs.CR
 |eprint=1411.6409
}}</ref>  The concept is based around an open repository containing separately encrypted metadata blocks and encrypted messages. Only the intended recipient is able to decrypt the metadata block, and having done so they can identify and download their messages and decrypt them.  Such a messaging system is at present in an experimental phase and not yet deployed.  Scaling this method would reveal to the third party only the inbox server being used by the recipient and the timestamp of sending and receiving.  The server could be shared by thousands of users, making social network modelling much more challenging.