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+This is the Zot! social communications protocol. 
+
+Specification revision: 1
+2 October 2011
+
+Mike Macgirvin
+This specification is public domain.
+
+Zot is a framework for secure delivery of messages on the web based on 
+webfinger and encapsulating salmon.
+
+First read the salmon and salmon magic envelope specifications. Zot also 
+makes use of webfinger and ActivityStreams and several concepts from RFC822
+(email). Zot encompasses the zot delivery framework and the zid remote
+access protocol.
+
+The current specification revision (1) is frozen until a reference 
+implementation is available. After that, any protocol changes will require a 
+change to the revision number.  
+
+****************
+* Zot delivery *
+****************
+
+Format of a zot wrapper. This completely encapsulates a salmon magic envelope 
+and provides privacy protection, while defining a delivery envelope - a 
+concept familiar to email systems. All addresses in zot are webfinger 
+resolvable addresses containing zot endpoints and salmon public keys (zot 
+is a superset of salmon). 
+
+
+<?xml version='1.0' encoding='UTF-8'?>
+<zot:msg xmlns:zot='http://purl.org/zot/1.0'>
+ <zot:key>((key))</zot:key>
+ <zot:iv>((iv))</zot:iv>
+ <zot:env_key>((env_key))</zot:env_key>
+ <zot:env_iv>((env_iv))</zot:env_iv>
+ <zot:env>((envelope))</zot:env>
+ <zot:sig key_id="xxx">((sender signature))</zot:sig>
+ <zot:alg>AES-256-CBC</zot:alg>
+ <zot:data type='application/magic-envelope+xml'>((salmon))</zot:data>
+</zot:msg>
+
+
+zot:key
+*******
+
+A suitable randomly generated encyption key of length 32 octets for encrypting 
+the salmon packet. This is then encrypted with the sender's private key and 
+base64url encoded.
+
+zot:iv
+******
+
+A suitable randomly generated initialisation vector of length 16 octets for 
+encrypting the salmon packet. This is then encrypted with the sender's private 
+key and base64url encoded.
+
+zot:env_key
+***********
+
+A suitable randomly generated encyption key of length 32 octets for encrypting 
+the envelope. This is then encrypted with the recipient's public key and 
+base64url encoded. For bulk deliveries, it is encrypted with the site bulk 
+delivery public key.
+
+
+zot:env_iv
+**********
+
+A suitable randomly generated initialisation vector of length 16 octets for 
+encrypting the envelope. This is then encrypted with the recipient's public
+key and base64url encoded. For bulk deliveries, it is encrypted with the site 
+bulk delivery public key.
+
+
+zot:env
+*******
+
+This consists of RFC822-style header fields representing the sender and 
+recipient(s). Line lengths have no defined limit and RFC822 continuation
+lines are not supported. If an inbound server is not able to process an
+envelope or post due to size constraints, it SHOULD return a 
+"413 Entity too large" HTTP response. 
+
+Example:
+
+Z-From: zot:bob@example.com
+Z-Sender: zot:bob@example.com
+Z-To: zot:alice@example.com
+
+Both "Z-From:" and "Z-Sender:" MUST be provided, and represent a single 
+webfinger address of the author and sender respectively. The webfinger
+address for the From address MUST contain a discoverable salmon public key 
+which is needed to verify the enclosed salmon data. Sender is used to indicate
+the webfinger identity responsible for transmitting this message. From
+indicates the message author. 
+
+In web-based social systems, a reply to a message SHOULD be conveyed to all of 
+the original message participants. Only the author of the original message 
+may know all the recipients (such as those contained in Bcc: elements). The 
+author of a message always provides 'From'. They MUST duplicate this 
+information as 'Sender' when posting a followup message.
+
+A reply to a given message MUST be sent to the From address of the original
+post, and MAY be sent to any additional addresses in the recipient list. The
+original post author MUST send the reply to all known recipients of the 
+original message, with their webfinger identity as Sender, and the 
+comment/reply author as From.   
+
+Receiving agents SHOULD validate the From identity as the signer of the salmon
+magic envelope, and MAY reject it. They SHOULD also verify the Sender signature
+of the zot packet if it is different than the salmon signature. They MAY 
+reject the message if the Sender is not allowed in their "friend list", or if 
+they do not have a suitable relationship with the Sender, or if either
+signature fails to validate. Rejected messages for one of these reasons SHOULD 
+be indicated with a "400 Bad Request" HTTP response.   
+
+
+Z-To: *
+
+indicates a public message with no specifically enumerated recipients.
+
+The fields Z-To: and/or Z-Bcc: MAY be present. At least one recipient field
+MUST be present.
+
+Z-To: zot:bob@example.com, zot:alice@example.com, mailto:dave@example.com 
+Z-Bcc: zot:https://example.com/profile/richard
+
+are valid entries. Adresses are comma separated and individual entries MUST NOT
+contain commas. There MAY be any number of ASCII space characters between
+entries for legibility. Header lines are terminated with a linefeed character
+(ASCII 0x0A). 
+
+This specification provides the following protocol address prefixes
+for use in Z-To: or Z-Bcc: elements:
+
+zot: - normal zot delivery using webfinger or LRDD resolvable address
+dfrn: - legacy DFRN mode delivery using webfinger or LRDD resovable address
+ostatus: - normal OStatus delivery using webfinger or LRDD resovable address
+diaspora: - Diaspora network delivery using webfinger address
+facebook: - Facebook profile page URL
+twitter: - Twitter personal page URL without AJAX '#!' fragment
+mailto: - email RFC822/ESMTP address
+
+Examples:
+
+twitter:http://twitter.com/bjensen
+facebook:http://facebook.com/profile.php?id=000000001
+
+Foreign protocol addresses which have not been defined in this specification 
+or future revisions of this specification and which are unknown to the
+recipient delivery process MAY be ignored.
+
+In cases where an address may contain either a webfinger or LRDD address, the
+webfinger address SHOULD be used preferentially. 
+
+
+Z-Bcc:
+******
+
+The Z-Bcc element may contain one or more addresses which are hidden from end
+user presentation. A zot receiving system MUST NOT store or allow for
+the display of the Bcc information. Implementations which require extreme
+privacy SHOULD send individual posts to each of the Bcc: recipients containing
+only a single address. They MAY send all Bcc: posts using bulk delivery, 
+however this may have privacy implications as there is no guarantee a
+receiving system will not log, store, or otherwise reveal the contents of the
+Bcc recipient list.
+
+Z-To: addresses MAY be shown to an end user.   
+ 
+
+Envelope encryption
+*******************
+
+
+The entire envelope is encrypted using alg with env_key and env_iv and
+base64url encoded for transmission.
+
+The zot envelope MAY include remote addresses. A zot inbound delivery agent
+MUST parse the envelope and determine whether a delivery address to the
+current endpoint is valid. This may be the result of:
+
+	1. An address contains the public message wildcard '*'
+
+	2. The current endpoint is a personal endpoint and one of the recipients
+listed in the Z-To: or Z-Bcc: addresses matches the webfinger address of
+the "owner" of the endpoint.
+
+	3. The current endpoint is a bulk delivery endpoint. The bulk delivery
+endpoint is defined elsewhere in this document. The bulk delivery agent
+will deliver to all local addresses found in the address lists. 
+
+zot:sig
+*******
+
+The Sender of the message signs the underlying salmon data in the manner 
+prescribed by salmon. If the Sender and From address are identical, the
+signature will be identical to the signature of the underlying salmon packet. 
+If they are different, this signature is verified with the Sender's public 
+key to verify the Sender. 
+
+zot:alg
+*******
+
+Currently the only valid choice for alg is "AES-256-CBC". 
+
+
+zot:data
+********
+
+The data field is a salmon magic envelope. This is encrypted with alg using 
+key and iv. The result is then base64url encoded for transmission.
+
+For the first release of this specification, the data format of the enclosed
+salmon SHOULD be 'application/atom+xml' representing an Atom formatted
+ActivityStream. Future revisions MAY allow other alternate data formats.
+All acceptable formats MUST be listed in an XRD property (described elsewhere
+in this document).  
+
+
+Delivery
+********
+
+The zot message is then POSTed to the zot endpoint URL as 
+application/text+xml and can be decoded/decrypted by the recipient using 
+their private key.
+
+The normal salmon endpoint for a service MAY be used as an alternate
+delivery method for non-encrypted (e.g. public) messages. 
+
+Discover of the zot endpoint is based on webfinger XRD:
+
+<Link rel="http://purl.org/zot/1.0/post" 
+	href="http://example/org/zot-endpoint" />
+
+
+Bulk Delivery
+*************
+
+A site MAY provide a bulk delivery endpoint, which MAY be used to avoid
+multiple encryptions of the same data for a single destination.
+This is discoverable by providing a zot endpoint with a corresponding
+salmon public key in the site's .well-known/host-meta file.
+A delivery to this endpoint will deliver to all local recipients provided
+within the zot envelope. 
+
+
+Extensibility
+*************
+
+This specification is subject to change. The current version which is in
+effect at a given site may be noted by XRD properties. The following 
+properties MUST be present in the XRD providing the relevant endpoint:
+
+<Property type="http://purl.org/zot/1.0/version">1</Property>
+<Property type="http://purl.org/zot/1.0/accept">application/atom+xml</Property>
+
+
+Version is specified in this document and indicates the current revision.
+Version is an increasing non-zero integer value. There are no minor versions. 
+Implementations MAY provide compatibility to multiple incompatible versions
+by using this version indication. The "accept" indicates a range of document
+content types which may be enclosed in the underlying salmon magic envelope.
+We anticipate this specification will in the future allow for a close variant
+of "message/rfc822" and which may include MIME. This may also be used to 
+embed alternate message formats and protocols such as 
+"application/x-diaspora+xml". If a delivery agent is unable to provide any
+acceptable data format to the remote system, the delivery to that system MUST
+be terminated/cancelled. 
+
+Foreign Messages
+****************
+
+Messages MAY be imported from other networks and systems which have no 
+knowledge of salmon signatures. The salmon signature in this case MUST be the
+exact string 'NOTSIGNED' to indicate that the author (From address) cannot be 
+validated using salmon verification. This message MUST be relayed by a Sender
+who can provide a valid salmon signature of the message via zot:sig. Delivery
+systems MAY reject foreign messages.  
+
+
+
+
+
+*******************************
+* Zid (Zot-ID) authentication *
+*******************************
+
+This section of the document is considered separate from the delivery 
+specification precding it and represents a different protocol, which is
+currently incomplete. This will be split off into another document in the
+future, but is presented here as a synergistic component of the Zot network
+model. 
+
+
+URLs may be present within a zot message which refer to private and/or
+protected resources. Zid uses OpenID to gain access to these protected
+resources. These could be private photos or profile information - or *any*
+web accessible resource. Using zid, these can have access controls which 
+extends to any resolvable webfinger address.
+
+Zid authentication relies on the presence of an OpenID provider element in
+webfinger, and a URL template which is applied to protected resources within
+a zot message.
+
+The template is designated with the characters "{zid=}" within a URL of a zot
+message. When the page is rendered for viewing to an observer, this template
+is replaced with the webfinger address of the viewer (if known), or an empty
+string if the webfinger address of the viewer cannot be determined.
+
+For example in a message body:
+
+http://example.com/photos/bob/picture.jpg?{zid=}
+
+refers to a private photo which is only visible to alice@example.com.
+
+If Alice is viewing the page, the link is rendered with
+
+http://example.com/photos/bob/picture.jpg?zid=alice@example.com
+
+If the page viewer is unknown, it is rendered as
+
+http://example.com/photos/bob/picture.jpg?zid=
+
+
+When the link is visited, the web server at example.com notes the presence of 
+the zid parameter and uses information from webfinger to locate the OpenID 
+provider for the zid webfinger address. It then redirects to the OpenID 
+server and requests authentication of the given person. If this is successful,
+access to the protected resource is granted.
+
+A browser cookie may be provided to avoid future authentication redirects
+and allow authenticated browsing to other resources on the website.
+
+Only authentication via OpenID is defined in this version of the specification.
+
+This can be used to provide access control of any web resource to any 
+webfinger identity on the internet.
+
+
+*********
+* Links *
+*********
+
+Salmon Protocol
+	http://www.salmon-protocol.org/salmon-protocol-summary
+
+Salmon Magic Envelope
+	http://salmon-protocol.googlecode.com/svn/trunk/draft-panzer-magicsig-01.html
+
+Atom Activity Stream Draft
+	http://activitystrea.ms/specs/atom/1.0/
+
+Activty Stream Base Schema
+	http://activitystrea.ms/head/activity-schema.html
+
+WebFinger Protocol
+	http://code.google.com/p/webfinger/wiki/WebFingerProtocol
+
+