[precis] draft evaluation of Resourceprep (RFC 3920)

[Peter Saint-Andre <[e-mail]>]

This message evaluates the Resourceprep profile of stringprep in
accordance with the template established by the PRECIS WG:

http://trac.tools.ietf.org/wg/precis/trac/wiki/StringprepReviewTemplate

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Specification:

   RFC 3920

Brief Description:

   - Resourcepart of JabberID ("JID"), as in:
     <localpart@domainpart/resourcepart>
   - Typically free-form text

How It's Used:

   - Device / session names (e.g., [e-mail]/Home)
   - Nicknames (e.g., [e-mail]/StPeter)

Who Generates It:

   - Often human users via an XMPP client
   - Often generated in an automated fashion by client or server

User Input Methods:

   - Typed by user
   - Copy-and-paste
   - Perhaps voice input

Enforcement:

   - Rules enforced by server / add-on service (e.g., chatroom
     service) on account login, joining a chatroom, etc.

Comparison Method:

   "Type 1" (byte-for-byte)

   (see http://tools.ietf.org/html/draft-ietf-precis-problem-statement )

Case Folding, Sensitivity, Preservation:

   - Strings are never folded
   - Case is preserved

Impact of Comparison:

   False positives:
     - interact with wrong device (e.g., for file transfer or voice call)
     - interact with wrong chatroom participant
     - improperly grant privileges (e.g., chatroom moderator)
     - allow communication with blocked entity

   False negatives:
     - unable to choose desired chatroom nick
     - unable to use granted privileges (e.g., chatroom moderator)
     - disallow communication with unblocked entity

Normalization:

   NFKC

Mapping:

   Spaces are mapped to nothing

Disallowed Characters:

   None

String Classes:

   - Basically a free-form identifier

Internal Structure:

   None

User Output:

   - text of message (e.g., in a chatroom)
   - device names often not exposed to human users

Operations:

  - Sometimes concatenated with other data and then
    used as input to a cryptographic hash function

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