2 This is the Zot! social communications protocol.
4 Specification revision: 1
8 This specification is public domain.
10 Zot is a framework for secure delivery of messages on the web based on
11 webfinger and encapsulating salmon.
13 First read the salmon and salmon magic envelope specifications. Zot also
14 makes use of webfinger and ActivityStreams and several concepts from RFC822
15 (email). Zot encompasses the zot delivery framework, and the zid remote
22 Format of a zot wrapper. This completely encapsulates a salmon magic envelope
23 and provides privacy protection, while defining a delivery envelope - a
24 concept familiar to email systems. All addresses in zot are webfinger
25 resolvable addresses containing both salmon and zot endpoints.
28 <?xml version='1.0' encoding='UTF-8'?>
29 <zot:msg xmlns:zot='http://purl.org/zot/1.0'>
30 <zot:key>((key))</zot:key>
31 <zot:iv>((iv))</zot:iv>
32 <zot:env>((envelope))</zot:env>
33 <zot:sig key_id="xxx">((sender signature))</zot:sig>
34 <zot:alg>AES-256-CBC</zot:alg>
35 <zot:data type='application/magic-envelope+xml'>((salmon))</zot:data>
42 A suitable randomly generated encyption key of length 32 octets for encrypting
43 the envelope and salmon packet. This is then encrypted with the sender's
44 private key and base64url encoded.
49 A suitable randomly generated initialisation vector of length 16 octets for
50 encrypting the envelope and salmon packet. This is then encrypted with the
51 sender's private key and base64url encoded.
56 This consists of RFC822-style header fields representing the sender and
57 recipient(s). Example:
60 Sender: bob@example.com
63 Both "From:" and "Sender:" MUST be provided, and represent a webfinger
64 address of the author and sender respectively. The webfinger address for
65 the From address MUST contain a discoverable salmon public key that
66 is needed to verify the enclosed salmon data. Sender is used to indicate
67 the webfinger identity responsible for transmitting this message. From
68 indicates the message author.
70 In web-based social systems, a reply to a message SHOULD be conveyed to all of
71 the original message participants. Only the author of the original message
72 may know all the recipients (such as those contained in Bcc: elements). The
73 author of a message always provides 'From'. They MUST duplicate this
74 information as 'Sender'.
76 A reply to a given message MUST be sent to the original From address, and MAY
77 be sent to any additional addresses in the recipient list. The original author
78 MUST send the reply to all known recipients of the original message, with
79 their webfinger identity as Sender, and the comment/reply author as From.
81 Receiving agents SHOULD validate the From identity as the signer of the salmon
82 magic envelope, and MAY reject it. They SHOULD also verify the Sender signature
83 of the zot packet if it is different than the salmon signature. They MAY
84 reject the message if the Sender is not allowed in their "friend list", or if
85 they do not have a suitable relationship with the Sender, or if either
86 signature fails to validate.
91 indicates a public message with no specifically enumerated recipients.
93 The fields To:, Cc:, and/or Bcc: MAY be present. At least one recipient field
94 MUST be present. These fields may use the entire syntax specified by RFC822,
97 To: "Bob Smith" <bob@example.com>, "Alice Jones" <alice@example.com>
99 is a valid entry. A zot envelope is UTF-8 encoded, which differs from RFC822.
100 The host component MUST be US-ASCII, with punycode translation of
101 internationalised domain names applied.
103 The entire envelope is encrypted with alg using key and iv. Only AES-256-CBC
104 is defined as an algorithm in this specification. The encrypted envelope is
105 then base64url encoded for transmission.
107 The zot envelope MAY include remote addresses. A zot delivery agent MUST parse
108 all addresses and determine whether a delivery address to the current endpoint
109 is valid. This may be the result of:
111 1. An address contains the public message wildcard '*'
113 2. The current endpoint is a personal endpoint and one of the recipients
114 listed in the To:, Cc:, or Bcc: addresses matches the webfinger address of
115 the "owner" of the endpoint.
117 3. The current endpoint is a bulk delivery endpoint. The bulk delivery
118 ednpoint is defined elsewhere in this document. The bulk delivery agent
119 will deliver to all local addresses found in the address lists.
124 The Sender of the message signs the underlying salmon data in the manner
125 prescribed by salmon. If the Sender and From address are identical, the
126 signature will be identical to the signature of the underlying salmon packet.
127 If they are different, this signature is verified with the Sender's public
128 key to verify the Sender.
133 Currently the only valid choice for alg is "AES-256-CBC".
139 The data field is a salmon magic envelope. This is encrypted with alg using
140 key and iv. The result is then base64url encoded for transmission.
142 For the first release of this specification, the data format of the enclosed
143 salmon SHOULD be 'application/atom+xml' representing an Atom formatted
144 ActivityStream. Future revisions MAY allow other alternate data formats.
145 All acceptable formats MUST be listed in an XRD property (described elsewhere
152 The zot message is then POSTed to the zot endpoint URL as
153 application/text+xml and can be decoded/decrypted by the recipient using
156 The normal salmon endpoint for a service MAY be used as an alternate
157 delivery method for non-encrypted (e.g. public) messages.
159 Discover of the zot endpoint is based on webfinger XRD:
161 <link rel="http://purl.org/zot/1.0/post"
162 href="http://example/org/zot-endpoint" />
168 A site MAY provide a bulk delivery endpoint, which MAY be used to avoid
169 multiple encryptions of the same data for a single destination.
170 This is discoverable by providing a zot endpoint with a corresponding
171 salmon public key in the site's .well-known/host-meta file.
172 A delivery to this endpoint will deliver to all local recipients provided
173 within the zot envelope.
179 This specification is subject to change. The current version which is in
180 effect at a given site may be noted by XRD properties. The following
181 properties MUST be present in the XRD providing the relevant endpoint:
183 <Property xmlns:zot="http://purl.og/zot/1.0"
184 type="http://purl.org/zot/1.0/version"
187 <Property xmlns:zot="http://purl.og/zot/1.0"
188 type="http://purl.org/zot/1.0/accept"
189 zot:accept="application/atom+xml" />
191 Version is specified in this document and indicates the current revision.
192 Implementations MAY provide compatibility to multiple incompatible versions
193 by using this version indication. The "accept" indicates a range of document
194 content types which may be enclosed in the underlying salmon magic envelope.
195 We anticipate this specification will in the future allow for a close variant
196 of "message/rfc822" and which may include MIME. This may also be used to
197 embed alternate message formats and protocols such as
198 "application/x-diaspora+xml". If a delivery agent is unable to provide any
199 acceptable data format, the delivery MUST be terminated/cancelled.
202 **********************
203 * Zid authentication *
204 **********************
206 URLs may be present within a zot message which refer to private and/or
207 protected resources. Zid uses OpenID to gain access to these protected
208 resources. These could be private photos or profile information - or *any*
209 web accessible resource. Using zid, these can have access controls which
210 extends to any resolvable webfinger address.
212 Zid authentication relies on the presence of an OpenID provider element in
213 webfinger, and a URL template which is applied to protected resources within
216 The template is designated with the characters "{zid=}" within a URL of a zot
217 message. When the page is rendered for viewing to an observer, this template
218 is replaced with the webfinger address of the viewer (if known), or an empty
219 string if the webfinger address of the viewer cannot be determined.
221 For example in a message body:
223 http://example.com/photos/bob/picture.jpg?{zid=}
225 refers to a private photo which is only visible to alice@example.com.
227 If Alice is viewing the page, the link is rendered with
229 http://example.com/photos/bob/picture.jpg?zid=alice@example.com
231 If the page viewer is unknown, it is rendered as
233 http://example.com/photos/bob/picture.jpg?zid=
236 When the link is visited, the web server at example.com notes the presence of
237 the zid parameter and uses information from webfinger to locate the OpenID
238 provider for the zid webfinger address. It then redirects to the OpenID
239 server and requests authentication of the given person. If this is successful,
240 access to the protected resource is granted.
242 A browser cookie may be provided to avoid future authentication redirects
243 and allow authenticated browsing to other resources on the website.
245 Only authentication via OpenID is defined in this version of the specification.
247 This can be used to provide access control to any web resource to any
248 webfinger identity on the internet.