1 This is the Zot! social communications protocol.
3 Specification revision: 1
7 This specification is public domain.
9 Zot is a framework for secure delivery of messages on the web based on
10 webfinger and encapsulating salmon.
12 First read the salmon and salmon magic envelope specifications. Zot also
13 makes use of webfinger and ActivityStreams and several concepts from RFC822
14 (email). Zot encompasses the zot delivery framework, and the zid remote
17 The current specification revision (1) is frozen until a reference
18 implementation is available. After that, any protocol changes will require a
19 change to the revision number.
25 Format of a zot wrapper. This completely encapsulates a salmon magic envelope
26 and provides privacy protection, while defining a delivery envelope - a
27 concept familiar to email systems. All addresses in zot are webfinger
28 resolvable addresses containing both salmon and zot endpoints.
31 <?xml version='1.0' encoding='UTF-8'?>
32 <zot:msg xmlns:zot='http://purl.org/zot/1.0'>
33 <zot:key>((key))</zot:key>
34 <zot:iv>((iv))</zot:iv>
35 <zot:env_key>((env_key))</zot:env_key>
36 <zot:env_iv>((env_iv))</zot:env_iv>
37 <zot:env>((envelope))</zot:env>
38 <zot:sig key_id="xxx">((sender signature))</zot:sig>
39 <zot:alg>AES-256-CBC</zot:alg>
40 <zot:data type='application/magic-envelope+xml'>((salmon))</zot:data>
47 A suitable randomly generated encyption key of length 32 octets for encrypting
48 the salmon packet. This is then encrypted with the sender's private key and
54 A suitable randomly generated initialisation vector of length 16 octets for
55 encrypting the salmon packet. This is then encrypted with the sender's private
56 key and base64url encoded.
61 A suitable randomly generated encyption key of length 32 octets for encrypting
62 the envelope. This is then encrypted with the recipient's public key and
63 base64url encoded. For bulk deliveries, it is encrypted with the site bulk
70 A suitable randomly generated initialisation vector of length 16 octets for
71 encrypting the envelope. This is then encrypted with the recipient's public
72 key and base64url encoded. For bulk deliveries, it is encrypted with the site
73 bulk delivery public key.
79 This consists of RFC822-style header fields representing the sender and
80 recipient(s). Example:
83 Sender: bob@example.com
86 Both "From:" and "Sender:" MUST be provided, and represent a webfinger
87 address of the author and sender respectively. The webfinger address for
88 the From address MUST contain a discoverable salmon public key that
89 is needed to verify the enclosed salmon data. Sender is used to indicate
90 the webfinger identity responsible for transmitting this message. From
91 indicates the message author.
93 In web-based social systems, a reply to a message SHOULD be conveyed to all of
94 the original message participants. Only the author of the original message
95 may know all the recipients (such as those contained in Bcc: elements). The
96 author of a message always provides 'From'. They MUST duplicate this
97 information as 'Sender'.
99 A reply to a given message MUST be sent to the original From address, and MAY
100 be sent to any additional addresses in the recipient list. The original author
101 MUST send the reply to all known recipients of the original message, with
102 their webfinger identity as Sender, and the comment/reply author as From.
104 Receiving agents SHOULD validate the From identity as the signer of the salmon
105 magic envelope, and MAY reject it. They SHOULD also verify the Sender signature
106 of the zot packet if it is different than the salmon signature. They MAY
107 reject the message if the Sender is not allowed in their "friend list", or if
108 they do not have a suitable relationship with the Sender, or if either
109 signature fails to validate.
114 indicates a public message with no specifically enumerated recipients.
116 The fields To:, Cc:, and/or Bcc: MAY be present. At least one recipient field
117 MUST be present. These fields may use the entire syntax specified by RFC822,
120 To: "Bob Smith" <bob@example.com>, "Alice Jones" <alice@example.com>
122 is a valid entry. A zot envelope is UTF-8 encoded, which differs from RFC822.
123 The host component MUST be US-ASCII, with punycode translation of
124 internationalised domain names applied.
126 The entire envelope is then encrypted using alg with env_key and env_iv and
127 base64url encoded for transmission.
129 The zot envelope MAY include remote addresses. A zot delivery agent MUST parse
130 all addresses and determine whether a delivery address to the current endpoint
131 is valid. This may be the result of:
133 1. An address contains the public message wildcard '*'
135 2. The current endpoint is a personal endpoint and one of the recipients
136 listed in the To:, Cc:, or Bcc: addresses matches the webfinger address of
137 the "owner" of the endpoint.
139 3. The current endpoint is a bulk delivery endpoint. The bulk delivery
140 endpoint is defined elsewhere in this document. The bulk delivery agent
141 will deliver to all local addresses found in the address lists.
146 The Sender of the message signs the underlying salmon data in the manner
147 prescribed by salmon. If the Sender and From address are identical, the
148 signature will be identical to the signature of the underlying salmon packet.
149 If they are different, this signature is verified with the Sender's public
150 key to verify the Sender.
155 Currently the only valid choice for alg is "AES-256-CBC".
161 The data field is a salmon magic envelope. This is encrypted with alg using
162 key and iv. The result is then base64url encoded for transmission.
164 For the first release of this specification, the data format of the enclosed
165 salmon SHOULD be 'application/atom+xml' representing an Atom formatted
166 ActivityStream. Future revisions MAY allow other alternate data formats.
167 All acceptable formats MUST be listed in an XRD property (described elsewhere
174 The zot message is then POSTed to the zot endpoint URL as
175 application/text+xml and can be decoded/decrypted by the recipient using
178 The normal salmon endpoint for a service MAY be used as an alternate
179 delivery method for non-encrypted (e.g. public) messages.
181 Discover of the zot endpoint is based on webfinger XRD:
183 <link rel="http://purl.org/zot/1.0/post"
184 href="http://example/org/zot-endpoint" />
190 A site MAY provide a bulk delivery endpoint, which MAY be used to avoid
191 multiple encryptions of the same data for a single destination.
192 This is discoverable by providing a zot endpoint with a corresponding
193 salmon public key in the site's .well-known/host-meta file.
194 A delivery to this endpoint will deliver to all local recipients provided
195 within the zot envelope.
201 This specification is subject to change. The current version which is in
202 effect at a given site may be noted by XRD properties. The following
203 properties MUST be present in the XRD providing the relevant endpoint:
205 <Property xmlns:zot="http://purl.og/zot/1.0"
206 type="http://purl.org/zot/1.0/version"
209 <Property xmlns:zot="http://purl.og/zot/1.0"
210 type="http://purl.org/zot/1.0/accept"
211 zot:accept="application/atom+xml" />
213 Version is specified in this document and indicates the current revision.
214 Implementations MAY provide compatibility to multiple incompatible versions
215 by using this version indication. The "accept" indicates a range of document
216 content types which may be enclosed in the underlying salmon magic envelope.
217 We anticipate this specification will in the future allow for a close variant
218 of "message/rfc822" and which may include MIME. This may also be used to
219 embed alternate message formats and protocols such as
220 "application/x-diaspora+xml". If a delivery agent is unable to provide any
221 acceptable data format, the delivery MUST be terminated/cancelled.
224 **********************
225 * Zid authentication *
226 **********************
228 URLs may be present within a zot message which refer to private and/or
229 protected resources. Zid uses OpenID to gain access to these protected
230 resources. These could be private photos or profile information - or *any*
231 web accessible resource. Using zid, these can have access controls which
232 extends to any resolvable webfinger address.
234 Zid authentication relies on the presence of an OpenID provider element in
235 webfinger, and a URL template which is applied to protected resources within
238 The template is designated with the characters "{zid=}" within a URL of a zot
239 message. When the page is rendered for viewing to an observer, this template
240 is replaced with the webfinger address of the viewer (if known), or an empty
241 string if the webfinger address of the viewer cannot be determined.
243 For example in a message body:
245 http://example.com/photos/bob/picture.jpg?{zid=}
247 refers to a private photo which is only visible to alice@example.com.
249 If Alice is viewing the page, the link is rendered with
251 http://example.com/photos/bob/picture.jpg?zid=alice@example.com
253 If the page viewer is unknown, it is rendered as
255 http://example.com/photos/bob/picture.jpg?zid=
258 When the link is visited, the web server at example.com notes the presence of
259 the zid parameter and uses information from webfinger to locate the OpenID
260 provider for the zid webfinger address. It then redirects to the OpenID
261 server and requests authentication of the given person. If this is successful,
262 access to the protected resource is granted.
264 A browser cookie may be provided to avoid future authentication redirects
265 and allow authenticated browsing to other resources on the website.
267 Only authentication via OpenID is defined in this version of the specification.
269 This can be used to provide access control of any web resource to any
270 webfinger identity on the internet.
278 http://www.salmon-protocol.org/salmon-protocol-summary
280 Salmon Magic Envelope
281 http://salmon-protocol.googlecode.com/svn/trunk/draft-panzer-magicsig-01.html
283 Atom Activity Stream Draft
284 http://activitystrea.ms/specs/atom/1.0/
286 Activty Stream Base Schema
287 http://activitystrea.ms/head/activity-schema.html
290 http://code.google.com/p/webfinger/wiki/WebFingerProtocol