<abstract>This specification defines a method that allows to use established encryption schemes for end-to-end encryption of Jingle transports.</abstract>
<remark><p>Accepted as Experimental by Council.</p></remark>
</revision>
<revision>
<version>0.0.1</version>
<date>2017-06-12</date>
<initials>vv</initials>
<remark><p>First draft</p></remark>
</revision>
</header>
<section1topic='Introduction'anchor='intro'>
<p>Jingle Encrypted Transports (JET) strives to provide a modular and easily extensible way to wrap Jingle Transports in an additional end-to-end encryption layer. The focus of this specification lays on being modular. It should be possible to extend existing Jingle use scenarios with end-to-end encryption by simply adding a JET element to the negotiation.</p>
</section1>
<section1topic='Terminology'anchor='terminology'>
<p>JET uses multiple encryption layers, so it is necessary to declare a distinct denomination for the different keys involved.</p>
<tablecaption='Denomination of keys used in the protocol'>
<tr>
<th>Designation</th>
<th>Abbrevation</th>
<th>Usage</th>
</tr>
<tr>
<td>Transport Key</td>
<td>TK</td>
<td>(Symmetric) key that is used to encrypt/decrypt the bytestreams sent/received through Jingle transports. This key encrypts the data two entities want to exchange. Examples for TK can be found under <linkurl='#ciphers'>"Ciphers"</link>.</td>
</tr>
<tr>
<td>Initialization Vector</td>
<td>IV</td>
<td>Initialization vector that is used together with TK.</td>
<td>Output element of an established end-to-end encryption method when encrypting TS.</td>
</tr>
</table>
</section1>
<section1topic='Principle'anchor='principle'>
<p>Lets assume Romeo wants to initiate an encrypted Jingle session with Juliet. Prior to the Jingle session initiation, an already existing, established and (ideally) authenticated end-to-end encryption session between Romeo and Juliet MUST exist. This session is needed to transfer the Transport Secret from Romeo to Juliet.</p>
<p>When this precondition is met, Romeo initially generates a transport key (TK) and associated initialization vector (IV). These will later be used by the sender to encrypt, and respectively by the recipient to decrypt data that is exchanged. This protocol defines a set of usable <linkurl='#ciphers'>ciphers</link> from which Romeo might choose. TK and IV together form the transport secret (TS).</p>
<p>Next Romeo uses his established encryption session with Juliet to encrypt TS. The resulting envelope element (EE) will be part of the Jingle session initiation as child of the JET &security;
<p>When Juliet receives Romeos session request, she decrypts EE to retrieve TS, from which she can obtain TK and IV. Now she and Romeo can go on with the session negotiation. Once the session is
<section1topic='Encrypted Jingle File Transfer using JET'anchor='jft'>
<p>&xep0234; has the disadvantage, that transmitted files are not encrypted (aside from regular TLS transport encryption), which means that intermediate nodes like XMPP/proxy server(s) have access to the transferred data. Considering that end-to-end encryption becomes more and more important to protect free speech and personal expression, this is a major flaw that needs to be addressed.</p>
<p>In this scenario Romeo wants to send an encrypted text file over to Juliet. First, he generates a fresh AES-256 transport key and IV. In this case TK and IV are serialized into TS which is then encrypted using Romeos end-to-end-encryption session with Juliet.</p>
<p>Juliet decrypts the envelope element (EE) using her session with Romeo to retrieve TS from which she deserializes TK and IV. Both Juliet and Romeo then carry on with the session negotiation as described in &xep0234;. Before Romeo starts transmitting the file, he encrypts it using TK and IV. He then transmitts the encrypted file over to Juliet.</p>
<p>When Juliet received the file, she uses the TK and IV to decrypt the received file.</p>
</section2>
<section2topic='File Request'>
<p>Juliet might want to request a file transfer from Romeo. This can be the case, when Romeo hosts the file. In order to do so, she sends generates TK and IV, creates TS from those and encrypts TS with an encryption method of her choice to get EE. TK and IV will be used by Romeo to encrypt the requested file before sending it to Juliet.</p>
<examplecaption="Juliet initiates an encrypted file request"><