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Internet Engineering Task Force                              C. Grothoff
Internet-Draft                                                  M. Wachs
Intended status: Informational                                 TU Munich
Expires: September 4, 2014                                  H. Wolf, Ed.
                                                           GNU consensus
                                                            J. Appelbaum
                                                        Tor Project Inc.
                                                          March 03, 2014


            Special-Use Domain Names of Peer-to-Peer Systems
              draft-grothoff-iesg-special-use-p2p-names-02

Abstract

   This is an IESG Approval document requesting the reservation of six
   Top-Level Domains for special use, in conformance with the
   registration procedure defined in RFC 6761, section 4.

   Peer-to-Peer systems use specific decentralized mechanisms to
   allocate, register, manage, and resolve names.  Those mechanisms
   operate entirely outside of DNS, independently from the DNS root and
   delegation tree.  In order to avoid interoperability issues with DNS
   as well as to address security and privacy concerns, this document
   describes six pseudo Top-Level Domain names (pTLDs), reserved for
   special use.

   The following six domains relate to security-focused peer-to-peer
   systems.  They are: ".gnu", ".zkey", ".onion", ".exit", ".i2p", and
   ".bit".

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on September 4, 2014.




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Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology and Conventions Used in This Document . . . . . .   3
   3.  Description of Special-Use Domains in P2P Networks  . . . . .   4
     3.1.  The ".gnu" Relative pTLD  . . . . . . . . . . . . . . . .   4
     3.2.  The ".zkey" Compressed Public Key pTLD  . . . . . . . . .   4
     3.3.  Geographically Anonymous pTLDs  . . . . . . . . . . . . .   4
       3.3.1.  The ".onion" Hidden Service pTLD  . . . . . . . . . .   4
       3.3.2.  The ".exit" Client Source Routing pTLD  . . . . . . .   5
     3.4.  The ".i2p" Addressbook pTLD . . . . . . . . . . . . . . .   5
     3.5.  The ".bit" Timeline System pTLD . . . . . . . . . . . . .   6
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
     5.1.  Domain Name Reservation Considerations for ".gnu."  . . .   7
     5.2.  Domain Name Reservation Considerations for ".zkey." . . .   8
     5.3.  Domain Name Reservation Considerations for ".onion."  . .  10
     5.4.  Domain Name Reservation Considerations for ".exit." . . .  11
     5.5.  Domain Name Reservation Considerations for ".bit."  . . .  13
     5.6.  Domain Name Reservation Considerations for ".i2p."  . . .  14
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  15
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  15
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  15
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  15
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  17

1.  Introduction

   Today, the Domain Name System (DNS) is a key service for the
   Internet.  DNS is primarily used to map human-memorable names to IP
   addresses, which are used for routing but generally not meaningful
   for humans.  However, the hierarchical nature of DNS makes it
   unsuitable for various Peer-to-Peer (P2P) Name Systems.  As



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   compatibility with applications using domain names is desired, these
   overlay networks often define exclusive alternative pseudo Top-Level
   Domains (pTLDs) to avoid conflict between the P2P namespace and the
   DNS hierarchy.

   The purpose of this document is to inform the Internet community
   about current practice of such pseudo-TLDs within peer-to-peer
   systems, and to normalize their usage according to the rules of RFC
   6761.  Given their decentralized design, such P2P systems do not
   require a central authority to register names nor do they belong to
   the DNS resolution tree.

   RFC 6761 defines a mechanism for reserving domain names for special
   use.  This document is an IESG Approval document requesting the
   reservation of six pTLDs for special use: ".gnu", ".zkey", ".onion",
   ".exit", ".i2p", and ".bit".

   The GNU Name System (GNS) (".gnu", ".zkey"), the Tor network
   (".onion", ".exit"), the Invisible Internet Project (".i2p"), and the
   Dot-Bit Project (".bit") use these pseudo-Top-Level Domains (pTLDs)
   to realize fully-decentralized and censorship-resistant secure
   alternatives for DNS or, in the case of the ".exit" pTLD, to control
   overlay routing and to securely specify path selection choices
   [TOR-PATH].

   To facilitate integration with legacy applications, the overlay's
   namespaces can be accessed from applications to resolve these special
   TLDs, for example via specialized SOCKS proxies [RFC1928],
   specialized DNS servers, or transparent name resolution and ephemeral
   address mapping.

2.  Terminology and Conventions Used in This Document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119.

   The word "peer" is used in the meaning of a individual system on the
   network.  Thus, "local peer" means the localhost.

   The acronym "pTLD" is used as a shortcut to mean a pseudo Top-Level
   Domain, i.e., a name or label for a network not allocated using
   common DNS procedures, and reserved with IANA for special use.

   In this document, ".tld" (with quotes) means: any domain or hostname
   within the scope of a given pTLD, while .tld (without quotes), or
   dot-tld, both refer to an adjective form.  For example, a collection
   of ".gnu" peers, but an .onion URL.  The pTLD itself is mentioned



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   with dot, and within double quotes, and usually followed by the word
   pTLD.

   The Tor-related names such as 'circuit', 'exit', 'node', 'relay',
   'stream', and related Tor terms are described in [Dingledine2004] and
   the Tor protocol specification [TOR-PROTOCOL].

3.  Description of Special-Use Domains in P2P Networks

3.1.  The ".gnu" Relative pTLD

   The ".gnu" pTLD is used to specify that a domain name should be
   resolved using GNS instead of DNS.  The GNS resolution process is
   documented in [Schanzenbach2012].  As GNS users need to install a GNS
   resolver on their individual system and as GNS resolution does not
   depend on DNS, there are no considerations for DNS with respect to
   the internals of the GNS resolution process itself.

3.2.  The ".zkey" Compressed Public Key pTLD

   The ".zkey" pTLD is used to signify that resolution of the given name
   MUST be performed using a record signed by an authority that is in
   possession of a particular public key.  Names in ".zkey" MUST end
   with a domain which is the compressed point representation from
   [EdDSA] on [Curve25519] of the public key of the authority, encoded
   using base32hex [RFC4648].  A GNS resolver uses the key to locate a
   record signed by the respective authority.

   The ".zkey" pTLD provides a (reverse) mapping from globally unique
   hashes to public key, therefore names in ".zkey" are non-memorable,
   and are expected to be hidden from the user [Schanzenbach2012].

3.3.  Geographically Anonymous pTLDs

   The Tor anonymization network makes use of several special pTLD
   labels, three of which have seen widespread usage to date
   [TOR-ADDRESS].

3.3.1.  The ".onion" Hidden Service pTLD

   The widely deployed ".onion" pTLD designates an anonymous Tor Hidden
   Service reachable via the Tor network [Dingledine2004].  These .onion
   URLs are self-authenticating addresses for use with any TCP service.
   Such addresses are typically resolved, reached and authenticated
   through transparent proxying or through a local SOCKS proxy running
   on TCP port 9050, TCP port 9150 or another user selected TCP port.
   The purpose of the Tor Hidden Services system is to provide
   geographic anonymity for the .onion host and for all clients visiting



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   the hidden service as well as other purposes such as NAT traversal,
   strong authentication, anonymity and censorship resistance.

   Addresses in ".onion" are opaque, non-mnemonic, alpha-semi-numeric
   hashes corresponding to an 80-bit truncated SHA1 hash over a given
   Tor hidden service's public key.  This hash can be made up of any
   letter of the alphabet and decimal digits beginning with 2 and ending
   with 7, thus representing a number in base32 [RFC4648].  Tor
   generates this "Onion key" automatically when the hidden service is
   configured.  Tor clients use it following the Tor Rendezvous
   specifications [TOR-RENDEZVOUS].

3.3.2.  The ".exit" Client Source Routing pTLD

   The dot-exit suffix is used as an in-band source routing control
   channel, usually for selection of a specific Tor relay during path
   creation as the last node in the Tor circuit.

   It may be used to access a DNS host via specific Torservers, in the
   form "hostname.nickname-or-fingerprint.exit", where the "hostname" is
   a valid hostname, and the "nickname-or-fingerprint" is either the
   nickname of a Tor relay in the Tor network consensus, or the hex-
   encoded SHA1 digest of the given node's public key (fingerprint).

   For example, "gnu.org.noisetor.exit" will route the client to
   "gnu.org" via the Tor node nicknamed "noisetor".  Using the
   fingerprint instead of the nickname ensures that the path selection
   uses a specific Tor exit node, and is harder to remember: e.g.,
   "gnu.org.f97f3b153fed6604230cd497a3d1e9815b007637.exit".

   When Tor sees an address in this format, it uses the specified
   "nickname-or-fingerprint" as the exit node.  If no "hostname"
   component is given, Tor defaults to the published IPv4 address of the
   Tor exit node [TOR-EXTSOCKS].

   Because "hostname" is allegedly valid, the total length of a dot-exit
   construct may exceed the maximum length allowed for domain names.
   Moreover, the resolution of "hostname" happens at the exit node.
   Trying to resolve such invalid domain names, including chaining dot-
   exit names will likely return a DNS lookup failure at the first exit
   node.

3.4.  The ".i2p" Addressbook pTLD








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   The ".i2p" pTLD provides accessibility to anonymous services
   ("eepsites") within the I2P network.  I2P is a scalable, self-
   organizing, resilient packet switched anonymous network layer, upon
   which any number of different anonymity or security-conscious
   applications can operate.

   The local I2P proxy resolves such names either by looking up a local
   table called the addressbook, or by decoding Base32-encoded [RFC4648]
   public keys and establishing a tunnel to the respective authority,
   similar to contacting .onion hidden services.  The details of I2P's
   operation [I2P-NAMING] are outside of the scope of this document.

   As the system is decentralized, "example.i2p" may also resolve
   differently for different peers, depending on the state of their
   respective addressbooks.

3.5.  The ".bit" Timeline System pTLD

   The ".bit" pTLD provides a name space where names are registered via
   transactions in the Namecoin currency [Namecoin].  Like Bitcoins,
   Namecoins are created using a proof-of-work calculation, which is
   also used to establish a decentralized, multi-party consensus on the
   valid transaction history, and thus the set of registered names and
   their values [SquareZooko].

   The Namecoin used in a transaction to register a name in ".bit" is
   lost.  This is not a fundamental problem as more coins can be
   generated via mining (proof-of-work calculations).  The registration
   cost is set to decrease over time, to prevent early adopters from
   registering too many names.

   The owner of a name can update the associated value by issuing an
   update, which is a transaction that uses a special coin which is
   generated as change during the registration operation.  If a name is
   not updated for a long time, the registration expires.

4.  Security Considerations

   Specific software performs the resolution of the six requested
   Special-Use Domain Names presented in this document; this resolution
   process happens outside of the scope of DNS.  Leakage of requests to
   such domains to the global operational DNS can cause interception of
   traffic that might be misused to monitor, censor, or abuse the user's
   trust, and lead to privacy issues with potentially dramatic
   consequences for the user.

   This RFC addresses another possible security concern, as the
   reservation of several Top-Level Domain names for these purposes will



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   minimize the possibility of confusion and conflict, and especially
   privacy risks for users.

5.  IANA Considerations

   The P2P Name Systems domains listed below, and any domains falling
   within those domains are Special-Use Domain Names [RFC6761]:

      gnu.

      zkey.

      onion.

      exit.

      i2p.

      bit.

5.1.  Domain Name Reservation Considerations for ".gnu."

   The ".gnu." domain is special according to RFC 6761, section 5
   [RFC6761], in the following ways:

   1.  Users MAY use these names as they would other domain names,
       entering them anywhere that they would otherwise enter a
       conventional DNS domain name.

       Since there is no central authority responsible for assigning
       dot-gnu names, and that specific domain is local to the local
       peer, users SHOULD be aware of that specificity.

       In any case, resolution in the dot-gnu pTLD returns DNS
       compatible results, and thus SHOULD NOT affect normal usage of
       most Internet applications.


   2.  Application Software MAY pass requests for dot-gnu domains for
       normal DNS resolution.  If available, the local resolver MUST
       intercept such requests within the respective operating system
       hooks and return DNS compatible results.  However, GNS-aware
       applications MAY choose to talk directly to the respective GNS
       resolver, and use this to access additional record types (with
       numbers above 65535) that are not defined in DNS.

       As mentioned in points 4. and 5. below, regular DNS resolution is
       expected to respond with NXDOMAIN.  Therefore, if it can



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       differentiate between DNS and P2P name resolution, application
       software MAY expect such a response, and MAY choose to treat
       other responses from the DNS as errors.


   3.  For legacy applications and legacy name resolution APIs expecting
       DNS resolution, no changes are required.

       However, Name Resolution APIs and Libraries MAY choose to support
       additional record types over time for the dot-gnu names.  They
       MAY choose to directly resolve those domains via appropriate APIs
       or mechanisms such as the GNS-specific resolution protocol.


   4.  Caching DNS servers SHOULD recognize dot-gnu names as special and
       SHOULD NOT, by default, attempt to look up NS records for them,
       or otherwise query authoritative DNS servers in an attempt to
       resolve dot-gnu names.  Instead, caching DNS servers SHOULD, by
       default, generate immediate negative responses for all such
       queries.


   5.  Authoritative DNS Servers are not expected to treat dot-gnu
       domain requests specially.  In practice, they MUST answer with
       NXDOMAIN, as dot-gnu is not available via global DNS resolution,
       and not doing so MAY put users' privacy at risk, e.g., as
       suggested in the next point.


   6.  DNS Server Operators SHOULD treat requests to the dot-gnu domain
       as errors, for correct installations MUST NOT allow such requests
       to escape to DNS.  DNS operators MUST NOT choose to redirect such
       requests to a site, not even to explain to the user that their
       P2P resolver is missing or mis-configured as this MAY violate
       privacy expectations of the user.


   7.  DNS Registries/Registrars

       In order to avoid conflicts with the P2P namespaces [SAC45], IANA
       reserves ".gnu." and thereby ensures that this label cannot be
       registered within the DNS tree, nor their management delegated to
       any particular organization.


5.2.  Domain Name Reservation Considerations for ".zkey."





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   The ".zkey." domain is special according to RFC 6761, section 5
   [RFC6761], in the following ways:

   1.  Users MAY use these names as they would other domain names,
       entering them anywhere that they would otherwise enter a
       conventional DNS domain name.

       Since there is no central authority necessary or possible for
       assigning dot-zkey names, and those names match cryptographic
       keys, users SHOULD be aware that they do not belong to regular
       DNS, but are still global in their scope.

       In any case, resolution in the dot-zkey pTLD returns DNS
       compatible results, and thus SHOULD NOT affect normal usage of
       most Internet applications.


   2.  Application Software MAY pass requests for dot-zkey domains for
       normal DNS resolution.  If available, the local resolver MUST
       intercept such requests within the respective operating system
       hooks and return DNS compatible results.  However, GNS-aware
       applications MAY choose to talk directly to the respective GNS
       resolver, and use this to access additional record types (with
       numbers above 65535) that are not defined in DNS.

       As mentioned in points 4. and 5. below, regular DNS resolution is
       expected to respond with NXDOMAIN.  Therefore, if it can
       differentiate between DNS and P2P name resolution, application
       software MAY expect such a response, and MAY choose to treat
       other responses from the DNS as errors.


   3.  For legacy applications and legacy name resolution APIs expecting
       DNS resolution, no changes are required.

       However, Name Resolution APIs and Libraries MAY choose to support
       additional record types over time for the dot-zkey names.  They
       MAY choose to directly resolve those domains via appropriate APIs
       or mechanisms such as the GNS-specific resolution protocol.


   4.  Caching DNS servers SHOULD recognize dot-zkey names as special
       and SHOULD NOT, by default, attempt to look up NS records for
       them, or otherwise query authoritative DNS servers in an attempt
       to resolve dot-zkey names.  Instead, caching DNS servers SHOULD,
       by default, generate immediate negative responses for all such
       queries.




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   5.  Authoritative DNS Servers are not expected to treat dot-zkey
       domain requests specially.  In practice, they MUST answer with
       NXDOMAIN, as dot-zkey is not available via global DNS resolution,
       and not doing so MAY put users' privacy at risk, e.g., as
       suggested in the next point.


   6.  DNS Server Operators SHOULD treat requests to the dot-zkey domain
       as errors, for correct installations MUST NOT allow such requests
       to escape to DNS.  DNS operators MUST NOT choose to redirect such
       requests to a site, not even to explain to the user that their
       P2P resolver is missing or mis-configured as this MAY violate
       privacy expectations of the user.


   7.  DNS Registries/Registrars

       In order to avoid conflicts with the P2P namespaces [SAC45], IANA
       reserves ".zkey." and thereby ensures that this label cannot be
       registered within the DNS tree, nor their management delegated to
       any particular organization.


5.3.  Domain Name Reservation Considerations for ".onion."

   The ".onion." domain is special according to RFC 6761, section 5
   [RFC6761], in the following ways:

   1.  Users MAY use these names as they would other domain names,
       entering them anywhere that they would otherwise enter a
       conventional DNS domain name.

       Since there is no central authority necessary or possible for
       assigning dot-onion names, and those names correspond to
       cryptographic keys, users SHOULD be aware that they do not belong
       to regular DNS, but are still global in their scope.

   2.  Application Software SHOULD NOT pass requests for dot-onion
       domains for normal DNS resolution.

       As mentioned in points 4. and 5. below, regular DNS resolution is
       expected to respond with NXDOMAIN.  Therefore, if it can
       differentiate between DNS and P2P name resolution, application
       software MAY expect such a response, and MAY choose to treat
       other responses from the DNS as errors.






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   3.  For legacy applications, the only way to resolve dot-onion
       domains properly is via a SOCKS proxy.  Using tools like
       TorSocks, SOCKS support can be added to legacy applications
       without changes to the application itself.


   4.  Caching DNS servers SHOULD recognize dot-onion names as special
       and SHOULD NOT, by default, attempt to look up NS records for
       them, or otherwise query authoritative DNS servers in an attempt
       to resolve dot-onion names.  Instead, caching DNS servers SHOULD,
       by default, generate immediate negative responses for all such
       queries.


   5.  Authoritative DNS Servers are not expected to treat dot-onion
       domain requests specially.  In practice, they MUST answer with
       NXDOMAIN, as dot-onion is not available via global DNS
       resolution, and not doing so MAY put users' privacy at risk,
       e.g., as suggested in the next point.


   6.  DNS Server Operators SHOULD treat requests to the dot-onion
       domain as errors, for correct installations MUST NOT allow such
       requests to escape to DNS.  DNS operators MUST NOT choose to
       redirect such requests to a site, not even to explain to the user
       that their P2P resolver is missing or mis-configured as this MAY
       violate privacy expectations of the user.


   7.  DNS Registries/Registrars

       In order to avoid conflicts with the P2P namespaces [SAC45], IANA
       reserves ".onion." and thereby ensures that this label cannot be
       registered within the DNS tree, nor their management delegated to
       any particular organization.


5.4.  Domain Name Reservation Considerations for ".exit."

   The ".exit." domain is special according to RFC 6761, section 5
   [RFC6761], in the following ways:

   1.  Users MAY use these names as they would other domain names,
       entering them anywhere that they would otherwise enter a
       conventional DNS domain name.

       Since dot-exit names correspond to a Tor-specific routing
       construct to reach target hosts via chosen Tor exit nodes, users



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       SHOULD be aware that they do not belong to regular DNS and that
       the actual target precedes the second-level domain name.

   2.  Application Software SHOULD NOT pass requests for dot-exit
       domains for normal DNS resolution.

       As mentioned in points 4. and 5. below, regular DNS resolution is
       expected to respond with NXDOMAIN.  Therefore, if it can
       differentiate between DNS and P2P name resolution, application
       software MAY expect such a response, and MAY choose to treat
       other responses from the DNS as errors.


   3.  For legacy applications, the only way to resolve dot-exit domains
       properly is via a SOCKS proxy.  Using tools like TorSocks, SOCKS
       support can be added to legacy applications without changes to
       the application itself.


   4.  Caching DNS servers SHOULD recognize dot-exit names as special
       and SHOULD NOT, by default, attempt to look up NS records for
       them, or otherwise query authoritative DNS servers in an attempt
       to resolve dot-exit names.  Instead, caching DNS servers SHOULD,
       by default, generate immediate negative responses for all such
       queries.


   5.  Authoritative DNS Servers are not expected to treat dot-exit
       domain requests specially.  In practice, they MUST answer with
       NXDOMAIN, as dot-exit is not available via global DNS resolution,
       and not doing so MAY put users' privacy at risk, e.g., as
       suggested in the next point.


   6.  DNS Server Operators SHOULD treat requests to the dot-exit domain
       as errors, for correct installations MUST NOT allow such requests
       to escape to DNS.  DNS operators MUST NOT choose to redirect such
       requests to a site, not even to explain to the user that their
       P2P resolver is missing or mis-configured as this MAY violate
       privacy expectations of the user.


   7.  DNS Registries/Registrars

       In order to avoid conflicts with the P2P namespaces [SAC45], IANA
       reserves ".exit." and thereby ensures that this label cannot be
       registered within the DNS tree, nor their management delegated to
       any particular organization.



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5.5.  Domain Name Reservation Considerations for ".bit."

   The ".bit." domain is special according to RFC 6761, section 5
   [RFC6761], in the following ways:

   1.  Users MAY use these names as they would other domain names,
       entering them anywhere that they would otherwise enter a
       conventional DNS domain name.

       From the user's perspective, the resolution of dot-bit pTLD is
       similar to the normal DNS resolution, and thus SHOULD NOT affect
       normal usage of most Internet applications.


   2.  Application Software MAY pass requests to the dot-bit pTLD for
       normal DNS resolution if A/AAAA records are desired.  If
       available, the local resolver MUST intercept such requests within
       the respective operating system hooks and return DNS compatible
       results.  However, NameCoin-aware applications MAY choose to talk
       directly to the respective P2P resolver, and use this to access
       additional record types that are not defined in DNS.


   3.  For legacy applications and legacy name resolution APIs expecting
       DNS resolution, no changes are required.

       However, Name Resolution APIs and Libraries MAY choose to support
       additional record types over time for the dot-bit domain.  They
       MAY choose to directly resolve those domains via blockchain-based
       resolution.


   4.  Caching DNS servers SHOULD recognize dot-bit names as special and
       SHOULD NOT, by default, attempt to look up NS records for them,
       or otherwise query authoritative DNS servers in an attempt to
       resolve dot-bit names.  Instead, caching DNS servers SHOULD, by
       default, generate immediate negative responses for all such
       queries.

       Given that dot-bit users typically have no special privacy
       expectations, and those names are globally unique, local caching
       DNS servers MAY choose to treat them as regular domain names, and
       cache the responses obtained from the Namecoin blockchain.  In
       that case however, NXDOMAIN results SHOULD NOT be cached, as new
       dot-bit domains may become active at any time.






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   5.  Authoritative DNS Servers are not expected to treat dot-bit
       domain requests specially.  In practice, they MUST answer with
       NXDOMAIN, as dot-bit is not available via global DNS resolution.


   6.  DNS Server Operators SHOULD treat requests to the dot-bit domain
       as errors, for correct installations SHOULD NOT allow such
       requests to escape to DNS.


   7.  DNS Registries/Registrars

       In order to avoid conflicts with the P2P namespaces [SAC45], IANA
       reserves ".bit." and thereby ensures that this label cannot be
       registered within the DNS tree, nor their management delegated to
       any particular organization.


5.6.  Domain Name Reservation Considerations for ".i2p."

   The ".i2p." domain is special according to RFC 6761, section 5
   [RFC6761], in the following ways:

   1.  Users MAY use these names as they would other domain names,
       entering them anywhere that they would otherwise enter a
       conventional DNS domain name.

       Since there is no central authority responsible for assigning
       dot-i2p names, and that the ultimate mapping is decided by the
       local peer, users SHOULD be aware of that specificity.

   2.  Application Software SHOULD NOT pass requests for dot-i2p domains
       for normal DNS resolution.

       As mentioned in points 4. and 5. below, regular DNS resolution is
       expected to respond with NXDOMAIN.  Therefore, if it can
       differentiate between DNS and P2P name resolution, application
       software MAY expect such a response, and MAY choose to treat
       other responses from the DNS as errors.


   3.  For legacy applications, the only way to resolve dot-i2p domains
       properly is via a SOCKS proxy.


   4.  Caching DNS servers SHOULD recognize dot-i2p names as special and
       SHOULD NOT, by default, attempt to look up NS records for them,
       or otherwise query authoritative DNS servers in an attempt to



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       resolve dot-i2p names.  Instead, caching DNS servers SHOULD, by
       default, generate immediate negative responses for all such
       queries.

   5.  Authoritative DNS Servers are not expected to treat dot-i2p
       domain requests specially.  In practice, they MUST answer with
       NXDOMAIN, as dot-i2p is not available via global DNS resolution,
       and not doing so MAY put users' privacy at risk, e.g., as
       suggested in the next point.


   6.  DNS Server Operators SHOULD treat requests to the dot-i2p domain
       as errors, for correct installations MUST NOT allow such requests
       to escape to DNS.  DNS operators MUST NOT choose to redirect such
       requests to a site, not even to explain to the user that their
       P2P resolver is missing or mis-configured as this MAY violate
       privacy expectations of the user.


   7.  DNS Registries/Registrars

       In order to avoid conflicts with the P2P namespaces [SAC45], IANA
       reserves ".i2p." and thereby ensures that this label cannot be
       registered within the DNS tree, nor their management delegated to
       any particular organization.


6.  Acknowledgements

   The authors thank the I2P developers for their constructive feedback,
   and Leif Ryge for his proof-reading and valuable feedback.

7.  References

7.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

   [RFC6761]  Cheshire, S. and M. Krochmal, "Special-Use Domain Names",
              RFC 6761, February 2013.

7.2.  Informative References




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   [Curve25519]
              Bernstein, D., "Curve25519: new Diffie-Hellman speed
              record", February 2006,
              <http://cr.yp.to/ecdh/curve25519-20060209.pdf>.

   [Dingledine2004]
              Dingledine, R., Mathewson, N., and P. Syverson, "Tor: the
              second-generation onion router", 2004, <https://www.onion-
              router.net/Publications/tor-design.pdf>.

   [EdDSA]    Bernstein, D., Duif, N., Lange, T., Schwabe, P., and Y.
              Yang, "High-speed, high-security signatures", September
              2011, <http://ed25519.cr.yp.to/ed25519-20110926.pdf>.

   [I2P-NAMING]
              Random, J., "Naming in I2P and Addressbook", 2003,
              <http://www.i2p2.de/naming.html>.

   [Namecoin]
              The .bit Project, "Namecoin DNS - DotBIT Project", 2013,
              <http://dot-bit.org/>.

   [RFC1928]  Leech, M., Ganis, M., Lee, Y., Kuris, R., Koblas, D., and
              L. Jones, "SOCKS Protocol Version 5", RFC 1928, March
              1996.

   [RFC4648]  Josefsson, S., "The Base16, Base32, and Base64 Data
              Encodings", RFC 4648, October 2006.

   [SAC45]    ICANN Security and Stability Advisory Committee, "Invalid
              Top Level Domain Queries at the Root Level of the Domain
              Name System", November 2010, <http://www.icann.org/en/
              groups/ssac/documents/sac-045-en.pdf>.

   [Schanzenbach2012]
              Schanzenbach, M., "Design and Implementation of a
              Censorship Resistant and Fully Decentralized Name System",
              September 2012.

   [SquareZooko]
              Swartz, A., "Squaring the Triangle: Secure, Decentralized,
              Human-Readable Names", 2011,
              <http://www.aaronsw.com/weblog/squarezooko>.

   [TOR-ADDRESS]
              Mathewson, N. and R. Dingledine, "Special Hostnames in
              Tor", September 2011, <https://gitweb.torproject.org/
              torspec.git/blob/HEAD:/address-spec.txt>.



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   [TOR-EXTSOCKS]
              Mathewson, N. and R. Dingledine, "Tor's extensions to the
              SOCKS protocol", September 2011, <https://
              gitweb.torproject.org/torspec.git/blob/HEAD:/socks-
              extensions.txt>.

   [TOR-PATH]
              Mathewson, N. and R. Dingledine, "Tor Path Specification",
              April 2013, <https://gitweb.torproject.org/torspec.git/
              blob/HEAD:/path-spec.txt>.

   [TOR-PROTOCOL]
              Dingledine, R. and N. Mathewson, "Tor Protocol
              Specification", November 2013, <https://
              gitweb.torproject.org/torspec.git/blob/HEAD:/tor-
              spec.txt>.

   [TOR-RENDEZVOUS]
              Mathewson, N. and R. Dingledine, "Tor Rendezvous
              Specification", September 2013, <https://
              gitweb.torproject.org/torspec.git/blob/HEAD:/rend-
              spec.txt>.

Authors' Addresses

   Christian Grothoff
   TU Munich
   Free Secure Network Systems Group
   Lehrstuhl fuer Netzarchitekturen und Netzdienste
   Boltzmannstrasse 3
   Technische Universitaet Muenchen
   Garching bei Muenchen, Bayern  D-85748
   DE

   Email: christian@grothoff.org


   Matthias Wachs
   TU Munich
   Free Secure Network Systems Group
   Lehrstuhl fuer Netzarchitekturen und Netzdienste
   Boltzmannstrasse 3
   Technische Universitaet Muenchen
   Garching bei Muenchen, Bayern  D-85748
   DE

   Email: wachs@net.in.tum.de




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   Hellekin O. Wolf (editor)
   GNU consensus

   Email: hellekin@gnu.org


   Jacob Appelbaum
   Tor Project Inc.

   Email: jacob@appelbaum.net









































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