Internet-Draft The GNU Name System November 2020
Schanzenbach, et al. Expires 14 May 2021 [Page]
Workgroup:
Independent Stream
Internet-Draft:
draft-schanzen-gns-02
Published:
Intended Status:
Informational
Expires:
Authors:
M. Schanzenbach
GNUnet e.V.
C. Grothoff
Berner Fachhochschule
B. Fix
GNUnet e.V.

The GNU Name System

Abstract

This document contains the GNU Name System (GNS) technical specification.

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 https://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 14 May 2021.

Table of Contents

1. Introduction

The Domain Name System (DNS) is a unique distributed database and a vital service for most Internet applications. While DNS is distributed, it relies on centralized, trusted registrars to provide globally unique names. As the awareness of the central role DNS plays on the Internet rises, various institutions are using their power (including legal means) to engage in attacks on the DNS, thus threatening the global availability and integrity of information on the Internet.

DNS was not designed with security as a goal. This makes it very vulnerable, especially to attackers that have the technical capabilities of an entire nation state at their disposal. This specification describes a censorship-resistant, privacy-preserving and decentralized name system: The GNU Name System (GNS). It is designed to provide a secure alternative to DNS, especially when censorship or manipulation is encountered. GNS can bind names to any kind of cryptographically secured token, enabling it to double in some respects as even as an alternative to some of today's Public Key Infrastructures, in particular X.509 for the Web.

This document contains the GNU Name System (GNS) technical specification of the GNU Name System [GNS], a fully decentralized and censorship-resistant name system. GNS provides a privacy-enhancing alternative to the Domain Name System (DNS). The design of GNS incorporates the capability to integrate and coexist with DNS. GNS is based on the principle of a petname system and builds on ideas from the Simple Distributed Security Infrastructure (SDSI), addressing a central issue with the decentralized mapping of secure identifiers to memorable names: namely the impossibility of providing a global, secure and memorable mapping without a trusted authority. GNS uses the transitivity in the SDSI design to replace the trusted root with secure delegation of authority thus making petnames useful to other users while operating under a very strong adversary model.

This document defines the normative wire format of resource records, resolution processes, cryptographic routines and security considerations for use by implementors. GNS requires a distributed hash table (DHT) for record storage. Specification of the DHT is out of scope of 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 [RFC2119].

2. Zones

A zone in GNS is defined by a zone type "ztype" that identifies a cryptosystem and a public/private key pair "(d,zk)", where "d" is the private key and "zk" the corresponding public key in the public key cipher identified by the "ztype". The contents of a zone are cryptographically signed before being published a distributed hash table (DHT). Records are grouped by their label and encrypted (Section 6.3) using an encryption key derived from the label and the zone public key. Instead of the zone private key "d", the signature MUST be created using a blinded public/private key pair "d'" and "zk'". This blinding is realized using a hierarchical deterministic key derivation (HDKD) scheme. Such a scheme allows the deterministic derivation of keys from the original public and private zone keys using "label" values. Specifically, the zone owner can derive private keys "d'", and a resolver to derive the corresponding public keys "zk'". Using different "label" values in the derivation results in different keys. Without knowledge of the "label" values, the different derivations are unlinkable both to the original key and to each other. This prevents zone enumeration and requires knowledge of both "zk" and the "label" to confirm affiliation with a specific zone. At the same time, the blinded "zk'" provides nodes with the ability to verifiy the integrity of the published information without disclosing the originating zone.

The following variables are associated with a zone in GNS:

ztype
is the unique type of the zone type as registered in the GNUnet Assigned Numbers Authority [GANA]. The zone type determines which cryptosystem is used for the asymmetric and symmetric key operations of the zone. A 32-bit number.
d
is the private zone key. The specific format depends on the zone type.
zk
is the public zone key. The specific format depends on the zone type.
zid
is the unique public identifier of a zone. It consists of the "ztype" and the public zone key "zk".
zTLD
is a string which encodes the "ztype" as well as the zone key "zk" into a domain name. The "zTLD" is used as a globally unique reference to a specific namespace in the process of name resolution.

The "zid" wire format is defined as follows:

0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|       ZONE TYPE       |      PUBLIC ZONE KEY  /
+-----+-----+-----+-----+                       /
/                                               /
/                                               /
Figure 1

For the string representation of the "zid", we use a base-32 encoding "StringEncode". However, instead of following [RFC4648] we base our character map on the optical character recognition friendly proposal of Crockford [CrockfordB32]. The only difference to Crockford is that the letter "U" decodes to the same base-32 value as the letter "V" (27).

zkl := <StringEncode(zid)>

If "zkl" is less than 63 characters, it is also the "zTLD". If the resulting "zkl" should be longer than 63 characters, the string must be divided into smaller labels separated by the label separator ".". Here, the most significant bytes of the "zid" must be contained in the rightmost label of the resulting string and the least significant bytes in the leftmost label of the resulting string. For example, assuming a "zkl" of 130 characters, the encoding would be:

zTLD := zkl[126:129].zkl[63:125].zkl[0:62]

3. Zone Types

A zone type identifies a family of eight functions:

Private-KeyGen() -> d
is a function to generate a fresh private key "d".
Public-KeyGen(d) -> zk
is a function to derive a public key "zk" from a private key "d".
HDKD-Private(d,label) -> d'
is an HDKD function which blinds a private zone key "d" using "label", resulting in another private key which can be used to create cryptographic signatures.
S-Encrypt(zk,label,nonce,expiration,rdata) -> bdata
is a deterministic symmetric encryption function which encrypts the record data "rdata" based on key material derived from "zk", "label", "nonce" and "expiration". A deterministic encryption scheme is required to improve performance by leveraging caching features of DHTs.
Sign(d',bdata) -> sig
is a function to sign "bdata" using the (blinded) private key "d'", yielding an unforgable cryptographic signature "sig".
HDKD-Public(zk,label) -> zk'
is a HDKD function which blinds a public zone key "zk" using "label". "zk" and "zk'" must be unlinkable. Furthermore, blinding "zk" with different values for "label" must result in unlinkable different resulting values for "zk'".
Verify(zk',bdata,sig) -> valid
is a function to verify the signature "sig" was created by the a private key "d'" derived from "d" and "label" if "zk'" was derived from the corresponding to "zk := Public-Keygen(d)" and "label". The function returns "true" if the signature is valid, and otherwise "false".
S-Decrypt(zk,label,nonce,expiration,bdata) -> rdata
is a symmetric encryption function which decrypts the encrypted record data "bdata" based on key material derived from "zk", "label", "nonce" and "expiration".

Zone types are identified by a 32-bit resource record type number. Resource record types are discussed in the next section.

4. Resource Records

A GNS implementor MUST provide a mechanism to create and manage resource records for local zones. A local zone is established by selecting a zone type and creating a zone key pair. Implementations SHOULD select a secure zone type automatically and not leave the zone type selection to the user. Records may be added to each zone, hence a (local) persistency mechanism for resource records and zones must be provided. This local zone database is used by the GNS resolver implementation and to publish record information.

A GNS resource record holds the data of a specific record in a zone. The resource record format is defined as follows:

0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|                   EXPIRATION                  |
+-----+-----+-----+-----+-----+-----+-----+-----+
|       DATA SIZE       |          TYPE         |
+-----+-----+-----+-----+-----+-----+-----+-----+
|           FLAGS       |        DATA           /
+-----+-----+-----+-----+                       /
/                                               /
/                                               /
Figure 2

where:

EXPIRATION
denotes the absolute 64-bit expiration date of the record. In microseconds since midnight (0 hour), January 1, 1970 in network byte order.
DATA SIZE
denotes the 32-bit size of the DATA field in bytes and in network byte order.
TYPE
is the 32-bit resource record type. This type can be one of the GNS resource records as defined in Section 4 or a DNS record type as defined in [RFC1035] or any of the complementary standardized DNS resource record types. This value must be stored in network byte order. Note that values below 2^16 are reserved for allocation via IANA ([RFC6895]), while values above 2^16 are allocated by the GNUnet Assigned Numbers Authority [GANA].
FLAGS
is a 32-bit resource record flags field (see below).
DATA
the variable-length resource record data payload. The contents are defined by the respective type of the resource record.

Flags indicate metadata surrounding the resource record. A flag value of 0 indicates that all flags are unset. The following illustrates the flag distribution in the 32-bit flag value of a resource record:

... 5       4         3        2        1        0
------+--------+--------+--------+--------+--------+
/ ... | SHADOW | EXPREL | SUPPL  | PRIVATE|    /   |
------+--------+--------+--------+--------+--------+
Figure 3

where:

SHADOW
If this flag is set, this record should be ignored by resolvers unless all (other) records of the same record type have expired. Used to allow zone publishers to facilitate good performance when records change by allowing them to put future values of records into the DHT. This way, future values can propagate and may be cached before the transition becomes active.
EXPREL
The expiration time value of the record is a relative time (still in microseconds) and not an absolute time. This flag should never be encountered by a resolver for records obtained from the DHT, but might be present when a resolver looks up private records of a zone hosted locally.
SUPPL
This is a supplemental record. It is provided in addition to the other records. This flag indicates that this record is not explicitly managed alongside the other records under the respective name but may be useful for the application. This flag should only be encountered by a resolver for records obtained from the DHT.
PRIVATE
This is a private record of this peer and it should thus not be published in the DHT. Thus, this flag should never be encountered by a resolver for records obtained from the DHT. Private records should still be considered just like regular records when resolving labels in local zones.

5. Record Types

A registry of GNS Record Types is described in Section 12. The registration policy for this registry is "First Come First Served", as described in [RFC8126].

5.1. PKEY

In GNS, a delegation of a label to a zone of type "PKEY" is represented through a PKEY record. The PKEY number is a zone type and thus also implies the cryptosystem for the zone that is being delegated to. A PKEY resource record contains the public key of the zone to delegate to. A PKEY record MUST be the only record under a label. No other records are allowed. A PKEY DATA entry has the following format:

0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|                   PUBLIC KEY                  |
|                                               |
|                                               |
|                                               |
+-----+-----+-----+-----+-----+-----+-----+-----+
Figure 4

where:

PUBLIC KEY
A 256-bit ECDSA zone key.

For PKEY zones the zone key material is derived using the curve parameters of the twisted edwards representation of Curve25519 [RFC7748] (a.k.a. edwards25519) with the ECDSA scheme ([RFC6979]). Consequently , we use the following naming convention for our cryptographic primitives for PKEY zones:

d
is a 256-bit ECDSA private zone key.
zk
is the ECDSA public zone key corresponding to d. It is defined in [RFC6979] as the curve point d*G where G is the group generator of the elliptic curve. The public key is used to uniquely identify a GNS zone and is referred to as the "zone key".
p
is the prime of edwards25519 as defined in [RFC7748], i.e. 2^255 - 19.
G
is the group generator (X(P),Y(P)) of edwards25519 as defined in [RFC7748].
L
is the prime-order subgroup of edwards25519 in [RFC7748].

The "zid" of a PKEY is 32 + 4 bytes in length. This means that a "zTLD" will always fit into a single label and does not need any further conversion.

Given a label, the output d' of the HDKD-Private(d,label) function for zone key blinding is calculated as follows for PKEY zones:

zk := d * G
PRK_h := HKDF-Extract ("key-derivation", zk)
h := HKDF-Expand (PRK_h, label | "gns", 512 / 8)
d' := h * d mod L

Equally, given a label, the output zk' of the HDKD-Public(zk,label) function is calculated as follows for PKEY zones:

PRK_h := HKDF-Extract ("key-derivation", zk)
h := HKDF-Expand (PRK_h, label | "gns", 512 / 8)
zk' := h mod L * zk

The PKEY cryptosystem uses a hash-based key derivation function (HKDF) as defined in [RFC5869], using HMAC-SHA512 for the extraction phase and HMAC-SHA256 for the expansion phase. "PRK_h" is key material retrieved using an HKDF using the string "key-derivation" as salt and the public zone key "zk" as initial keying material. "h" is the 512-bit HKDF expansion result. The expansion info input is a concatenation of the label and string "gns". "label" is a UTF-8 string under which the resource records are published.

We point out that the multiplication of "zk" with "h" is a point multiplication, while the multiplication of "d" with "h" is a scalar multiplication.

The Sign() and Verify() functions for PKEY zones are implemented using 512-bit ECDSA deterministic signatures as specified in [RFC6979].

The S-Encrypt() and S-Decrypt() functions use AES in counter mode as defined in [MODES] (CTR-AES-256):

RDATA := CTR-AES256(K, IV, BDATA)
BDATA := CTR-AES256(K, IV, RDATA)

The key "K" and counter "IV" are derived from the record "label" and the zone key "zk" as follows:

PRK_k := HKDF-Extract ("gns-aes-ctx-key", zk)
PRK_n := HKDF-Extract ("gns-aes-ctx-iv", zk)
K := HKDF-Expand (PRK_k, label, 256 / 8);
NONCE := HKDF-Expand (PRK_n, label, 32 / 8)

HKDF is a hash-based key derivation function as defined in [RFC5869]. Specifically, HMAC-SHA512 is used for the extraction phase and HMAC-SHA256 for the expansion phase. The output keying material is 32 octets (256 bits) for the symmetric key and 4 octets (32 bits) for the nonce. The symmetric key "K" is a 256-bit AES [RFC3826] key.

The nonce is combined with a 64-bit initialization vector and a 32-bit block counter as defined in [RFC3686]. The block counter begins with the value of 1, and it is incremented to generate subsequent portions of the key stream. The block counter is a 32-bit integer value in network byte order. The initialization vector is the expiration time of the resource record block in network byte order. The resulting counter ("IV") wire format is as follows:

0     8     16    24    32
+-----+-----+-----+-----+
|         NONCE         |
+-----+-----+-----+-----+
|       EXPIRATION      |
|                       |
+-----+-----+-----+-----+
|      BLOCK COUNTER    |
+-----+-----+-----+-----+
Figure 5

5.2. EDKEY

In GNS, a delegation of a label to a zone of type "EDKEY" is represented through a EDKEY record. The EDKEY number is a zone type and thus also implies the cryptosystem for the zone that is being delegated to. An EDKEY resource record contains the public key of the zone to delegate to. A EDKEY record MUST be the only record under a label. No other records are allowed. A EDKEY DATA entry has the following format:

0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|                   PUBLIC KEY                  |
|                                               |
|                                               |
|                                               |
+-----+-----+-----+-----+-----+-----+-----+-----+
Figure 6

where:

PUBLIC KEY
A 256-bit EdDSA zone key.

For EDKEY zones the zone key material is derived using the curve parameters of the twisted edwards representation of Curve25519 [RFC7748] (a.k.a. edwards25519) with the Ed25519-SHA-512 scheme [ed25519]. Consequently , we use the following naming convention for our cryptographic primitives for EDKEY zones:

d
is a 256-bit EdDSA private zone key.
a
is is an integer derived from "d" using the SHA512 hash function as defined in [ed25519].
zk
is the EdDSA public zone key corresponding to "d". It is defined in [ed25519] as the curve point "a*G" where "G" is the group generator of the elliptic curve and "a" is an integer derived from "d" using the SHA512 hash function. The public key is used to uniquely identify a GNS zone and is referred to as the "zone key".
p
is the prime of edwards25519 as defined in [RFC7748], i.e. 2^255 - 19.
G
is the group generator (X(P),Y(P)) of edwards25519 as defined in [RFC7748].
L
is the prime-order subgroup of edwards25519 in [RFC7748].

The "zid" of an EDKEY is 32 + 4 bytes in length. This means that a "zTLD" will always fit into a single label and does not need any further conversion.

The "EDKEY" HDKD instantiation is based on [Tor224]. Given a label, the output of the HDKD-Private function for zone key blinding is calculated as follows for EDKEY zones:

zk := a * G
PRK_h := HKDF-Extract ("key-derivation", zk)
h := HKDF-Expand (PRK_h, label | "gns", 512 / 8)
h[31] &= 7
a1 := a / 8 /* 8 is the cofactor of Curve25519 */
a2 := h * a1 mod L
a' = a2 * 8 /* 8 is the cofactor of Curve25519 */

Equally, given a label, the output of the HDKD-Public function is calculated as follows for PKEY zones:

PRK_h := HKDF-Extract ("key-derivation", zk)
h := HKDF-Expand (PRK_h, label | "gns", 512 / 8)
h[31] &= 7  // Implies h mod L == h
zk' := h * zk

We note that implementors must employ a constant time scalar multiplication for the constructions above. Also, implementors must ensure that the private key "a" is an ed25519 private key and specifically that "a[0] & 7 == 0" holds.

The EDKEY cryptosystem uses a hash-based key derivation function (HKDF) as defined in [RFC5869], using HMAC-SHA512 for the extraction phase and HMAC-SHA256 for the expansion phase. "PRK_h" is key material retrieved using an HKDF using the string "key-derivation" as salt and the public zone key "zk" as initial keying material. "h" is the 512-bit HKDF expansion result. The expansion info input is a concatenation of the label and string "gns". The result of the HKDF must be clamped. "a" is the 256-bit integer corresponding to the 256-bit private zone key "d". "label" is a UTF-8 string under which the resource records are published.

We point out that the multiplication of "zk" with "h" is a point multiplication, while the division and multiplication of "a" and "a1" with the cofactor are integer operations.

Signatures for EDKEY zones using the derived private key "a'" are NOT compliant with [ed25519]. Instead, signatures MUST be generated as follows for any given message M and deterministic random-looking "r":

R := r * G
S := r + SHA512(R, zk', M) * a' mod L

A signature (R,S) is valid if the following holds:

SB == R + SHA512(R, zk', M) * A'

The S-Encrypt() and S-Decrypt() functions use ChaCha20 as defined in [RFC7539] (ChaCha20-Poly1305):

RDATA := ChaCha20(K, IV, BDATA)
BDATA := ChaCha20(K, IV, RDATA) = CIPHERTEXT | TAG

The result of the ChaCha20 encryption function is the encrypted ciphertext concatenated with the 128-bit authentication tag "TAG". Accordingly, the length of BDATA equals the length of the RDATA plus the 16 octets of the authentication tag.

The key "K" and counter "IV" are derived from the record "label" and the zone key "zk" as follows:

PRK_k := HKDF-Extract ("gns-aes-ctx-key", zk)
PRK_n := HKDF-Extract ("gns-aes-ctx-iv", zk)
K := HKDF-Expand (PRK_k, label, 256 / 8);
NONCE := HKDF-Expand (PRK_n, label, 32 / 8)

HKDF is a hash-based key derivation function as defined in [RFC5869]. Specifically, HMAC-SHA512 is used for the extraction phase and HMAC-SHA256 for the expansion phase. The output keying material is 32 octets (256 bits) for the symmetric key and 4 octets (32 bits) for the NONCE. The symmetric key "K" is a 256-bit ChaCha20 [RFC7539] key. No additional authenticated data (AAD) is used.

The nonce is combined with a 64-bit initialization vector and a 32-bit block counter. The block counter begins with the value of 1, and it is incremented to generate subsequent portions of the key stream. The block counter is a 32-bit integer value treated as a 32-bit little-endian integer. The initialization vector is the expiration time of the resource record block in network byte order. The resulting counter ("IV") wire format is as follows:

0     8     16    24    32
+-----+-----+-----+-----+
|         NONCE         |
+-----+-----+-----+-----+
|       EXPIRATION      |
|                       |
+-----+-----+-----+-----+
|      BLOCK COUNTER    |
+-----+-----+-----+-----+
Figure 7

5.3. GNS2DNS

It is possible to delegate a label back into DNS through a GNS2DNS record. The resource record contains a DNS name for the resolver to continue with in DNS followed by a DNS server. Both names are in the format defined in [RFC1034] for DNS names. A GNS2DNS DATA entry has the following format:

0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|                    DNS NAME                   |
/                                               /
/                                               /
|                                               |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                 DNS SERVER NAME               |
/                                               /
/                                               /
|                                               |
+-----------------------------------------------+
Figure 8

where:

DNS NAME
The name to continue with in DNS (0-terminated).
DNS SERVER NAME
The DNS server to use. May be an IPv4/IPv6 address in dotted decimal form or a DNS name. It may also be a relative GNS name ending with a "+" top-level domain. The value is UTF-8 encoded (also for DNS names) and 0-terminated.

5.4. LEHO

Legacy hostname records can be used by applications that are expected to supply a DNS name on the application layer. The most common use case is HTTP virtual hosting, which as-is would not work with GNS names as those may not be globally unique. A LEHO resource record is expected to be found together in a single resource record with an IPv4 or IPv6 address. A LEHO DATA entry has the following format:

0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|                 LEGACY HOSTNAME               |
/                                               /
/                                               /
|                                               |
+-----+-----+-----+-----+-----+-----+-----+-----+
Figure 9

where:

LEGACY HOSTNAME
A UTF-8 string (which is not 0-terminated) representing the legacy hostname.

NOTE: If an application uses a LEHO value in an HTTP request header (e.g. "Host:" header) it must be converted to a punycode representation [RFC5891].

5.5. NICK

Nickname records can be used by zone administrators to publish an indication on what label this zone prefers to be referred to. This is a suggestion to other zones what label to use when creating a delegation record (Section 3) containing this zone's public zone key. This record SHOULD only be stored under the empty label "@" but MAY be returned with record sets under any label as a supplemental record. Section 8.2.6 details how a resolver must process supplemental and non-supplemental NICK records. A NICK DATA entry has the following format:

0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|                  NICKNAME                     |
/                                               /
/                                               /
|                                               |
+-----+-----+-----+-----+-----+-----+-----+-----+
Figure 10

where:

NICKNAME
A UTF-8 string (which is not 0-terminated) representing the preferred label of the zone. This string MUST NOT include a "." character.

5.6. BOX

In GNS, every "." in a name delegates to another zone, and GNS lookups are expected to return all of the required useful information in one record set. This is incompatible with the special labels used by DNS for SRV and TLSA records. Thus, GNS defines the BOX record format to box up SRV and TLSA records and include them in the record set of the label they are associated with. For example, a TLSA record for "_https._tcp.example.org" will be stored in the record set of "example.org" as a BOX record with service (SVC) 443 (https) and protocol (PROTO) 6 (tcp) and record TYPE "TLSA". For reference, see also [RFC2782]. A BOX DATA entry has the following format:

0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|   PROTO   |    SVC    |       TYPE            |
+-----------+-----------------------------------+
|                 RECORD DATA                   |
/                                               /
/                                               /
|                                               |
+-----+-----+-----+-----+-----+-----+-----+-----+
Figure 11

where:

PROTO
the 16-bit protocol number, e.g. 6 for tcp. In network byte order.
SVC
the 16-bit service value of the boxed record, i.e. the port number. In network byte order.
TYPE
is the 32-bit record type of the boxed record. In network byte order.
RECORD DATA
is a variable length field containing the "DATA" format of TYPE as defined for the respective TYPE in DNS.

5.7. VPN

A VPN DATA entry has the following format:

0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|          HOSTING PEER PUBLIC KEY              |
|                (256 bits)                     |
|                                               |
|                                               |
+-----------+-----------------------------------+
|   PROTO   |    SERVICE  NAME                  |
+-----------+                                   +
/                                               /
/                                               /
|                                               |
+-----+-----+-----+-----+-----+-----+-----+-----+
Figure 12

where:

HOSTING PEER PUBLIC KEY
is a 256-bit EdDSA public key identifying the peer hosting the service.
PROTO
the 16-bit protocol number, e.g. 6 for TCP. In network byte order.
SERVICE NAME
a shared secret used to identify the service at the hosting peer, used to derive the port number requird to connect to the service. The service name MUST be a 0-terminated UTF-8 string.

6. Publishing Records

GNS resource records are published in a distributed hash table (DHT). We assume that a DHT provides two functions: GET(key) and PUT(key,value). In GNS, resource records are grouped by their respective labels, encrypted and published together in a single resource records block (RRBLOCK) in the DHT under a key "q": PUT(q, RRBLOCK). The key "q" which is derived from the zone key "zk" and the respective "label" of the contained records.

6.1. DHT Key Derivations

Given a label, the DHT key "q" is derived as follows:

q := SHA512 (HDKD-Public(zk, label))
label
is a UTF-8 string under which the resource records are published.
zk
is the public zone key.
q
Is the 512-bit DHT key under which the resource records block is published. It is the SHA512 hash over the derived public zone key.

6.2. Resource Records Block

GNS records are grouped by their labels and published as a single block in the DHT. The grouped record sets MAY be paired with any number of supplemental records. Supplemental records must have the supplemental flag set (See Section 4). The contained resource records are encrypted using a symmetric encryption scheme. A GNS implementation must publish RRBLOCKs in accordance to the properties and recommendations of the underlying DHT. This may include a periodic refresh publication. A GNS RRBLOCK has the following format:

0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|       ZONE TYPE       |    PUBLIC ZONE KEY    |
+-----+-----+-----+-----+       (BLINDED)       |
/                                               /
/                                               /
|                                               |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                   SIGNATURE                   |
/                                               /
/                                               /
|                                               |
+-----+-----+-----+-----+-----+-----+-----+-----+
|         SIZE          |       PURPOSE         |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                   EXPIRATION                  |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                    BDATA                      /
/                                               /
/                                               |
+-----+-----+-----+-----+-----+-----+-----+-----+
Figure 13

where:

ZONE TYPE
is the 32-bit zone type.
ZONE PUBLIC KEY
is the blinded public zone key "HDKD-Public(zk, label)" to be used to verify SIGNATURE.
SIGNATURE
The signature is computed over the data following the PUBLIC KEY field. The signature is created using the Sign() function of the cryptosystem of the zone and the derived private key "HDKD-Private(d, label)" (see Section 3).
SIZE
A 32-bit value containing the length of the signed data following the PUBLIC KEY field in network byte order. This value always includes the length of the fields SIZE (4), PURPOSE (4) and EXPIRATION (8) in addition to the length of the BDATA. While a 32-bit value is used, implementations MAY refuse to publish blocks beyond a certain size significantly below 4 GB. However, a minimum block size of 62 kilobytes MUST be supported.
PURPOSE
A 32-bit signature purpose flag. This field MUST be 15 (in network byte order).
EXPIRATION
Specifies when the RRBLOCK expires and the encrypted block SHOULD be removed from the DHT and caches as it is likely stale. However, applications MAY continue to use non-expired individual records until they expire. The value MUST be set to the expiration time of the resource record contained within this block with the smallest expiration time. If a records block includes shadow records, then the maximum expiration time of all shadow records with matching type and the expiration times of the non-shadow records is considered. This is a 64-bit absolute date in microseconds since midnight (0 hour), January 1, 1970 in network byte order.
BDATA
The encrypted resource records with a total size of SIZE - 16.

6.3. Record Data Encryption and Decryption

A symmetric encryption scheme is used to encrypt the resource records set RDATA into the BDATA field of a GNS RRBLOCK. The wire format of the RDATA looks as follows:

0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|     RR COUNT          |        EXPIRA-        /
+-----+-----+-----+-----+-----+-----+-----+-----+
/         -TION         |       DATA SIZE       |
+-----+-----+-----+-----+-----+-----+-----+-----+
|         TYPE          |          FLAGS        |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                      DATA                     /
/                                               /
/                                               |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                   EXPIRATION                  |
+-----+-----+-----+-----+-----+-----+-----+-----+
|       DATA SIZE       |          TYPE         |
+-----+-----+-----+-----+-----+-----+-----+-----+
|           FLAGS       |        DATA           /
+-----+-----+-----+-----+                       /
/                       +-----------------------/
/                       |                       /
+-----------------------+                       /
/                     PADDING                   /
/                                               /
Figure 14

where:

RR COUNT
A 32-bit value containing the number of variable-length resource records which are following after this field in network byte order.
EXPIRATION, DATA SIZE, TYPE, FLAGS and DATA
These fields were defined in the resource record format in Section 4. There MUST be a total of RR COUNT of these resource records present.
PADDING
The padding MUST contain the value 0 in all octets. The padding MUST ensure that the size of the RDATA WITHOUT the RR COUNT field is a power of two. As a special exception, record sets with (only) a zone delegation record type are never padded. Note that a record set with a delegation record MUST NOT contain other records.

7. Internationalization and Character Encoding

All labels in GNS are encoded in UTF-8 [RFC3629]. This does not include any DNS names found in DNS records, such as CNAME records, which are internationalized through the IDNA specifications [RFC5890].

8. Name Resolution

Names in GNS are resolved by recursively querying the DHT record storage. In the following, we define how resolution is initiated and each iteration in the resolution is processed.

GNS resolution of a name must start in a given starting zone indicated using a zone public key. Details on how the starting zone may be determined is discussed in Section 10.

When GNS name resolution is requested, a desired record type MAY be provided by the client. The GNS resolver will use the desired record type to guide processing, for example by providing conversion of VPN records to A or AAAA records, if that is desired. However, filtering of record sets according to the required record types MUST still be done by the client after the resource record set is retrieved.

8.1. Recursion

In each step of the recursive name resolution, there is an authoritative zone zk and a name to resolve. The name may be empty. Initially, the authoritative zone is the start zone. If the name is empty, it is interpreted as the apex label "@".

From here, the following steps are recursively executed, in order:

  1. Extract the right-most label from the name to look up.
  2. Calculate q using the label and zk as defined in Section 6.1.
  3. Perform a DHT query GET(q) to retrieve the RRBLOCK.
  4. Verify and process the RRBLOCK and decrypt the BDATA contained in it as defined in Section 6.3.

Upon receiving the RRBLOCK from the DHT, apart from verifying the provided signature, the resolver MUST check that the authoritative zone key was used to sign the record: The derived zone key "h*zk" MUST match the public key provided in the RRBLOCK, otherwise the RRBLOCK MUST be ignored and the DHT lookup GET(q) MUST continue.

8.2. Record Processing

Record processing occurs at the end of a single recursion. We assume that the RRBLOCK has been cryptographically verified and decrypted. At this point, we must first determine if we have received a valid record set in the context of the name we are trying to resolve:

  1. Case 1: If the remainder of the name to resolve is empty and the record set does not consist of a delegation, CNAME or DNS2GNS record, the record set is the result and the recursion is concluded.
  2. Case 2: If the name to be resolved is of the format "_SERVICE._PROTO" and the record set contains one or more matching BOX records, the records in the BOX records are the result and the recusion is concluded (Section 8.2.4).
  3. Case 3: If the remainder of the name to resolve is not empty and does not match the "_SERVICE._PROTO" syntax, then the current record set MUST consist of a single delegation record (Section 8.2.1), a single CNAME record (Section 8.2.3), or one or more GNS2DNS records (Section 8.2.2), which are processed as described in the respective sections below. The record set may include any number of supplemental records. Otherwise, resolution fails and the resolver MUST return an empty record set. Finally, after the recursion terminates, the client preferences for the record type SHOULD be considered. If a VPN record is found and the client requests an A or AAAA record, the VPN record SHOULD be converted (Section 8.2.5) if possible.

8.2.1. Encountering zone delegation records

When the resolver encounters a record of a supported zone delegation record type (such as PKEY or EDKEY) and the remainder of the name is not empty, resolution continues recursively with the remainder of the name in the GNS zone specified in the delegation record. Implementations MUST NOT allow multiple different zone type delegations under a single label. Implementations MAY support any subset of zone types. If an unsupported zone type is encountered, resolution fails (NXDOMAIN).

If the remainder of the name to resolve is empty and we have received a record set containing only a single PKEY record, the recursion is continued with the PKEY as authoritative zone and the empty apex label "@" as remaining name, except in the case where the desired record type is PKEY, in which case the PKEY record is returned and the resolution is concluded without resolving the empty apex label.

8.2.2. GNS2DNS

When a resolver encounters one or more GNS2DNS records and the remaining name is empty and the desired record type is GNS2DNS, the GNS2DNS records are returned.

Otherwise, it is expected that the resolver first resolves the IP(s) of the specified DNS name server(s). GNS2DNS records MAY contain numeric IPv4 or IPv6 addresses, allowing the resolver to skip this step. The DNS server names may themselves be names in GNS or DNS. If the DNS server name ends in ".+", the rest of the name is to be interpreted relative to the zone of the GNS2DNS record. If the DNS server name ends in a label representation of a zone key, the DNS server name is to be resolved against the GNS zone zk.

Multiple GNS2DNS records may be stored under the same label, in which case the resolver MUST try all of them. The resolver MAY try them in any order or even in parallel. If multiple GNS2DNS records are present, the DNS name MUST be identical for all of them, if not the resolution fails and an emtpy record set is returned as the record set is invalid.

Once the IP addresses of the DNS servers have been determined, the DNS name from the GNS2DNS record is appended to the remainder of the name to be resolved, and resolved by querying the DNS name server(s). As the DNS servers specified are possibly authoritative DNS servers, the GNS resolver MUST support recursive resolution and MUST NOT delegate this to the authoritative DNS servers. The first successful recursive name resolution result is returned to the client. In addition, the resolver returns the queried DNS name as a supplemental LEHO record (Section 5.4) with a relative expiration time of one hour.

GNS resolvers SHOULD offer a configuration option to disable DNS processing to avoid information leakage and provide a consistent security profile for all name resolutions. Such resolvers would return an empty record set upon encountering a GNS2DNS record during the recursion. However, if GNS2DNS records are encountered in the record set for the apex and a GNS2DNS record is expicitly requested by the application, such records MUST still be returned, even if DNS support is disabled by the GNS resolver configuration.

8.2.3. CNAME

If a CNAME record is encountered, the canonical name is appended to the remaining name, except if the remaining name is empty and the desired record type is CNAME, in which case the resolution concludes with the CNAME record. If the canonical name ends in ".+", resolution continues in GNS with the new name in the current zone. Otherwise, the resulting name is resolved via the default operating system name resolution process. This may in turn again trigger a GNS resolution process depending on the system configuration.

The recursive DNS resolution process may yield a CNAME as well which in turn may either point into the DNS or GNS namespace (if it ends in a label representation of a zone key). In order to prevent infinite loops, the resolver MUST implement loop detections or limit the number of recursive resolution steps. If the last CNAME was a DNS name, the resolver returns the DNS name as a supplemental LEHO record (Section 5.4) with a relative expiration time of one hour.

8.2.4. BOX

When a BOX record is received, a GNS resolver must unbox it if the name to be resolved continues with "_SERVICE._PROTO". Otherwise, the BOX record is to be left untouched. This way, TLSA (and SRV) records do not require a separate network request, and TLSA records become inseparable from the corresponding address records.

8.2.5. VPN

At the end of the recursion, if the queried record type is either A or AAAA and the retrieved record set contains at least one VPN record, the resolver SHOULD open a tunnel and return the IPv4 or IPv6 tunnel address, respectively. The type of tunnel depends on the contents of the VPN record data. The VPN record MUST be returned if the resolver implementation does not support setting up a tunnnel.

8.2.6. NICK

NICK records are only relevant to the recursive resolver if the record set in question is the final result which is to be returned to the client. The encountered NICK records may either be supplemental (see Section 4) or non-supplemental. If the NICK record is supplemental, the resolver only returns the record set if one of the non-supplemental records matches the queried record type.

The differentiation between a supplemental and non-supplemental NICK record allows the client to match the record to the authoritative zone. Consider the following example:

Query: alice.example (type=A)
Result:
A: 192.0.2.1
NICK: eve
Figure 15

In this example, the returned NICK record is non-supplemental. For the client, this means that the NICK belongs to the zone "alice.doe" and is published under the empty label along with an A record. The NICK record should be interpreted as: The zone defined by "alice.doe" wants to be referred to as "eve". In contrast, consider the following:

Query: alice.example (type=AAAA)
Result:
AAAA: 2001:DB8::1
NICK: john (Supplemental)
Figure 16

In this case, the NICK record is marked as supplemental. This means that the NICK record belongs to the zone "doe" and is published under the label "alice" along with an A record. The NICK record should be interpreted as: The zone defined by "doe" wants to be referred to as "john". This distinction is likely useful for other records published as supplemental.

9. Zone Revocation

Whenever a recursive resolver encounters a new GNS zone, it MUST check against the local revocation list whether the respective zone key has been revoked. If the zone key was revoked, the resolution MUST fail with an empty result set.

In order to revoke a zone key, a signed revocation object SHOULD be published. This object MUST be signed using the private zone key. The revocation object is flooded in the overlay network. To prevent flooding attacks, the revocation message MUST contain a proof of work (PoW). The revocation message including the PoW MAY be calculated ahead of time to support timely revocation.

For all occurences below, "Argon2id" is the Password-based Key Derivation Function as defined in [Argon2]. For the PoW calculations the algorithm is instantiated with the following parameters:

S
The salt. Fixed 16-octet string: "GnsRevocationPow".
t
Number of iterations: 3
m
Memory size in KiB: 1024
T
Output length of hash in bytes: 64
p
Parallelization parameter: 1
v
Algorithm version: 0x13
y
Algorithm type (Argon2id): 2
X
Unused
K
Unused

The following is the message string "P" on which the PoW is calculated:

0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|                      POW                      |
+-----------------------------------------------+
|                   TIMESTAMP                   |
+-----------------------------------------------+
|       ZONE TYPE       |    PUBLIC ZONE KEY    |
+-----+-----+-----+-----+                       |
/                                               /
/                                               /
+-----+-----+-----+-----+-----+-----+-----+-----+
Figure 17

where:

POW
A 64-bit solution to the PoW. In network byte order.
TIMESTAMP
denotes the absolute 64-bit date when the revocation was computed. In microseconds since midnight (0 hour), January 1, 1970 in network byte order.
PUBLIC KEY
is the 256-bit public key "zk" of the zone which is being revoked and the key to be used to verify SIGNATURE. The wire format of this value is defined in [RFC8032], Section 5.1.5.

Traditionally, PoW schemes require to find a "POW" such that at least D leading zeroes are found in the hash result. D is then referred to as the "difficulty" of the PoW. In order to reduce the variance in time it takes to calculate the PoW, we require that a number "Z" different PoWs must be found that on average have "D" leading zeroes.

The resulting proofs may then published and disseminated. The concrete dissemination and publication methods are out of scope of this document. Given an average difficulty of "D", the proofs have an expiration time of EPOCH. With each additional bit difficulty, the lifetime of the proof is prolonged for another EPOCH. Consequently, by calculating a more difficult PoW, the lifetime of the proof can be increased on demand by the zone owner.

The parameters are defined as follows:

Z
The number of PoWs required is fixed at 32.
D
The difficulty is fixed at 22.
EPOCH
A single epoch is fixed at 365 days.

Given that proof has been found, a revocation data object is defined as follows:

0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|                   TIMESTAMP                   |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                      TTL                      |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                     POW_0                     |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                       ...                     |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                     POW_Z-1                   |
+-----------------------------------------------+
|       ZONE TYPE       |    PUBLIC ZONE KEY    |
+-----+-----+-----+-----+                       |
/                                               /
/                                               /
+-----+-----+-----+-----+-----+-----+-----+-----+
|                   SIGNATURE                   |
/                                               /
/                                               /
|                                               |
+-----+-----+-----+-----+-----+-----+-----+-----+
Figure 18

where:

TIMESTAMP
denotes the absolute 64-bit date when the revocation was computed. In microseconds since midnight (0 hour), January 1, 1970 in network byte order. This is the same value as the timestamp used in the individual PoW calculations.
TTL
denotes the relative 64-bit time to live of of the record in microseconds also in network byte order. This field is informational for a verifier. The verifier may discard revocation if the TTL indicates that it is already expired. However, the actual TTL of the revocation must be determined by examining the leading zeros in the proof of work calculation.
POW_i
The values calculated as part of the PoW, in network byte order. Each POW_i MUST be unique in the set of POW values. To facilitate fast verification of uniqueness, the POW values must be given in strictly monotonically increasing order in the message.
ZONE TYPE
The 32-bit zone type corresponding to the zone public key.
ZONE PUBLIC KEY
is the public key "zk" of the zone which is being revoked and the key to be used to verify SIGNATURE.
SIGNATURE
A signature over a timestamp and the public zone zk of the zone which is revoked and corresponds to the key used in the PoW. The signature is created using the Sign() function of the cryptosystem of the zone and the private zone key (see Section 3).

The signature over the public key covers a 32-bit pseudo header conceptually prefixed to the public key. The pseudo header includes the key length and signature purpose:

0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|         SIZE (0x30)   |       PURPOSE (0x03)  |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                   TIMESTAMP                   |
+-----+-----+-----+-----+-----+-----+-----+-----+
|       ZONE TYPE       |     ZONE PUBLIC KEY   |
+-----+-----+-----+-----+                       |
/                                               /
/                                               /
+-----+-----+-----+-----+-----+-----+-----+-----+
Figure 19

where:

SIZE
A 32-bit value containing the length of the signed data in bytes in network byte order.
PURPOSE
A 32-bit signature purpose flag. This field MUST be 3 (in network byte order).
ZONE TYPE
The 32-bit zone type corresponding to the zone public key.
ZONE PUBLIC KEY / TIMESTAMP
Both values as defined in the revocation data object above.

In order to verify a revocation the following steps must be taken, in order:

  1. The current time MUST be between TIMESTAMP and TIMESTAMP+TTL.
  2. The signature MUST match the public key.
  3. The set of POW values MUST NOT contain duplicates.
  4. The average number of leading zeroes resulting from the provided POW values D' MUST be greater than D.
  5. The validation period (TTL) of the revocation is calculated as (D'-D) * EPOCH * 1.1. The EPOCH is extended by 10% in order to deal with unsynchronized clocks. The TTL added on top of the TIMESTAMP yields the expiration date.

10. Determining the Root Zone and Zone Governance

The resolution of a GNS name must start in a given start zone indicated to the resolver using any public zone key. The local resolver may have a local start zone configured/hard-coded which points to a local or remote start zone key. A resolver client may also determine the start zone from the suffix of the name given for resolution or using information retrieved out of band. The governance model of any zone is at the sole discretion of the zone owner. However, the choice of start zone(s) is at the sole discretion of the local system administrator or user.

This is an important distinguishing factor from the Domain Name System where root zone governance is centralized at the Internet Corporation for Assigned Names and Numbers (ICANN). In DNS terminology, GNS roughly follows the idea of a hyper-hyper local root zone deployment, with the difference that it is not expected that all deployments use the same local root zone.

In the following, we give examples how a local client resolver SHOULD discover the start zone. The process given is not exhaustive and clients MAY suppliement it with other mechanisms or ignore it if the particular application requires a different process.

GNS clients MUST first try to interpret the top-level domain of a GNS name as a zone key representation ("zTLD"). If the top-level domain is indicated to be a label representation of a public zone key with a well-defined "ztype" value, the root zone of the resolution process is implicitly given by the suffic of the name:

Example name: www.example.<zTLD>
=> Root zone: zk of type ztype
=> Name to resolve from root zone: www.example

In GNS, users MAY own and manage their own zones. Each local zone SHOULD be associated with a single GNS label, but users MAY choose to use longer names consisting of multiple labels. If the name of a locally managed zone matches the suffix of the name to be resolved, resolution SHOULD start from the respective local zone:

Example name: www.example.org
Local zones:
fr = (d0,zk0)
gnu = (d1,zk1)
com = (d2,zk2)
...
=> Entry zone: zk1
=> Name to resolve from entry zone: www.example

Finally, additional "suffix to zone" mappings MAY be configured. Suffix to zone key mappings SHOULD be configurable through a local configuration file or database by the user or system administrator. The suffix MAY consist of multiple GNS labels concatenated with a ".". If multiple suffixes match the name to resolve, the longest matching suffix MUST BE used. The suffix length of two results cannot be equal, as this would indicate a misconfiguration. If both a locally managed zone and a configuration entry exist for the same suffix, the locally managed zone MUST have priority.

Example name: www.example.org
Local suffix mappings:
gnu = zk0
example.org = zk1
example.com = zk2
...
=> Entry zone: zk1
=> Name to resolve from entry zone: www

11. Security Considerations

11.1. Cryptography

The security of cryptographic systems depends on both the strength of the cryptographic algorithms chosen and the strength of the keys used with those algorithms. The security also depends on the engineering of the protocol used by the system to ensure that there are no non-cryptographic ways to bypass the security of the overall system.

This document concerns itself with the selection of cryptographic algorithms for use in GNS. The algorithms identified in this document are not known to be broken (in the cryptographic sense) at the current time, and cryptographic research so far leads us to believe that they are likely to remain secure into the foreseeable future. However, this isn't necessarily forever, and it is expected that new revisions of this document will be issued from time to time to reflect the current best practices in this area.

GNS PKEY zone keys use ECDSA over Curve25519. This is an unconventional choice, as ECDSA is usually used with other curves. However, traditional ECDSA curves are problematic for a range of reasons described in the Curve25519 and EdDSA papers. Using EdDSA directly is also not possible, as a hash function is used on the private key which destroys the linearity that the GNU Name System depends upon. We are not aware of anyone suggesting that using Curve25519 instead of another common curve of similar size would lower the security of ECDSA. GNS uses 256-bit curves because that way the encoded (public) keys fit into a single DNS label, which is good for usability.

In terms of crypto-agility, whenever the need for an updated cryptographic scheme arises to, for example, replace ECDSA over Curve25519 for PKEY records it may simply be introduced through a new record type. Such a new record type may then replace the delegation record type for future records. The old record type remains and zones can iteratively migrate to the updated zone keys.

In order to ensure ciphertext indistinguishability, care must be taken with respect to the initialization vector in the counter block. In our design, the IV is always the expiration time of the record block. For blocks with relative expiration times it is implicitly ensured that each time a block is published into the DHT, its IV is unique as the expiration time is calculated dynamically and increases monotonically. For blocks with absolute expiration times, the implementation MUST ensure that the expiration time is modified when the record data changes. For example. the expiration time may be increased by a single microsecond.

11.2. Abuse mitigation

GNS names are UTF-8 strings. Consequently, GNS faces similar issues with respect to name spoofing as DNS does for internationalized domain names. In DNS, attackers may register similar sounding or looking names (see above) in order to execute phishing attacks. GNS zone administrators must take into account this attack vector and incorporate rules in order to mitigate it.

Further, DNS can be used to combat illegal content on the internet by having the respective domains seized by authorities. However, the same mechanisms can also be abused in order to impose state censorship, which ist one of the motivations behind GNS. Hence, such a seizure is, by design, difficult to impossible in GNS. In particular, GNS does not support WHOIS ([RFC3912]).

11.3. Zone management

In GNS, zone administrators need to manage and protect their zone keys. Once a zone key is lost it cannot be recovered. Once it is compromised it cannot be revoked (unless a revocation message was pre-calculated and is still available). Zone administrators, and for GNS this includes end-users, are required to responsibly and dilligently protect their cryptographic keys. Offline signing is in principle possible, but GNS does not support separate zone signing and key-signing keys (as in [RFC6781]) in order to provide usable security.

Similarly, users are required to manage their local root zone. In order to ensure integrity and availability or names, users must ensure that their local root zone information is not compromised or outdated. It can be expected that the processing of zone revocations and an initial root zone is provided with a GNS client implementation ("drop shipping"). Extension and customization of the zone is at the full discretion of the user.

11.4. Impact of underlying DHT

This document does not specifiy the properties of the underlying distributed hash table (DHT) which is required by any GNS implementation. For implementors, it is important to note that the properties of the DHT are directly inherited by the GNS implementation. This includes both security as well as other non-functional properties such as scalability and performance. Implementors should take great care when selecting or implementing a DHT for use in a GNS implementation. DHTs with strong security and performance guarantees exist [R5N]. It should also be taken into consideration that GNS implementations which build upon different DHT overlays are unlikely to be interoperable with each other.

11.5. Revocations

Zone administrators are advised to pre-generate zone revocations and securely store the revocation information in case the zone key is lost, compromised or replaced in the furture. Pre-calculated revocations may become invalid due to expirations or protocol changes such as epoch adjustments. Consequently, implementors and users must make precautions in order to manage revocations accordingly.

Revocation payloads do NOT include a 'new' key for key replacement. Inclusion of such a key would have two major disadvantages:

If revocation is used after a private key was compromised, allowing key replacement would be dangerous: if an adversary took over the private key, the adversary could then broadcast a revocation with a key replacement. For the replacement, the compromised owner would have no chance to issue even a revocation. Thus, allowing a revocation message to replace a private key makes dealing with key compromise situations worse.

Sometimes, key revocations are used with the objective of changing cryptosystems. Migration to another cryptosystem by replacing keys via a revocation message would only be secure as long as both cryptosystems are still secure against forgery. Such a planned, non-emergency migration to another cryptosystem should be done by running zones for both ciphersystems in parallel for a while. The migration would conclude by revoking the legacy zone key only once it is deemed no longer secure, and hopefully after most users have migrated to the replacement.

12. GANA Considerations

GANA [GANA] is requested to create an "GNU Name System Record Types" registry. The registry shall record for each entry:

The registration policy for this sub-registry is "First Come First Served", as described in [RFC8126]. GANA is requested to populate this registry as follows:

Number | Name    | Contact | References | Description
-------+---------+---------+------------+-------------------------
65536  | PKEY    | N/A     | [This.I-D] | GNS zone delegation
65537  | NICK    | N/A     | [This.I-D] | GNS zone nickname
65538  | LEHO    | N/A     | [This.I-D] | GNS legacy hostname
65539  | VPN     | N/A     | [This.I-D] | VPN resolution
65540  | GNS2DNS | N/A     | [This.I-D] | Delegation to DNS
65541  | BOX     | N/A     | [This.I-D] | Boxed record
Figure 20

GANA is requested to amend the "GNUnet Signature Purpose" registry as follows:

Purpose | Name            | References | Description
--------+-----------------+------------+--------------------------
  3     | GNS_REVOCATION  | [This.I-D] | GNS zone key revocation
 15     | GNS_RECORD_SIGN | [This.I-D] | GNS record set signature
Figure 21

13. Test Vectors

The following represents a test vector for a record set with a DNS record of type "A" as well as a GNS record of type "PKEY" under the label "test".


Zone private key (d, little-endian, with ztype prepended):
0001000020110ab2
807d702f7b86dc30
6c37e8e2e0a5dbb2
7ae934727d9ca07d
69c73579

Zone identifier (zid):
0001000063db8bf0
44212617ce5db4fc
7c06fb9e35b2e177
3b4b76c05b42a1e7
17d018c6

Encoded zone identifier (zkl = zTLD):
000G0033VE5Z0H114RBWWQDMZHY0DYWY6PSE2XSV9DVC0PT2M7KHFM0RRR

Label: test
RRCOUNT: 2

Record #0
EXPIRATION: 1602865000130231
DATA_SIZE: 4
TYPE: 1
FLAGS: 0
DATA:
01020304

Record #1
EXPIRATION: 1602865000130231
DATA_SIZE: 32
TYPE: 65536
FLAGS: 2
DATA:
00010000796f4a8b
66d7780f62f46604
24c750295f31674d
052a4989cf0779a7

RDATA:
0005b1cc16f4a6b7
0000000400000001
0000000001020304
0005b1cc16f4a6b7
0000002000010000
0000000200010000
796f4a8b66d7780f
62f4660424c75029
5f31674d052a4989
cf0779a700000000
0000000000000000
0000000000000000
0000000000000000
0000000000000000
0000000000000000
0000000000000000

BDATA:
4f20986bde1fbbed
b57196c1c23e35e9
f1ee62207de81297
0c2b370a9980042f
e8296cdd8ca66d69
11ebb2f3b2550959
7cb781ef56ac07d1
7c5dd0903bb94c67
c07e100079f59db3
3363fe110f435838
ef482e60b527f553
2ee435e4c0525439
3965d3dbe72e7c92
9bb4172b3bda7270
06c33578682cb212
23ac2cf389a4fbab
bb8cb55e

RRBLOCK:
000100007bc2eb40
ef056b05a5a84c35
241ca7190284a4a4
f5afdae14e8b784c
4b516dd6082d7969
2d2bbcb1328bc1df
270b2c02693bdaa9
f4d496dd850068d4
3a471fac0156b902
3536e54960fac47b
58762d82c5ad8e7f
34a121819c7ca75d
64c78d3a00000094
0000000f0005b1cc
16f4a6b74f20986b
de1fbbedb57196c1
c23e35e9f1ee6220
7de812970c2b370a
9980042fe8296cdd
8ca66d6911ebb2f3
b25509597cb781ef
56ac07d17c5dd090
3bb94c67c07e1000
79f59db33363fe11
0f435838ef482e60
b527f5532ee435e4
c05254393965d3db
e72e7c929bb4172b
3bda727006c33578
682cb21223ac2cf3
89a4fbabbb8cb55e

The following is an example revocation for a zone:


Zone private key (d, little-endian scalar, with ztype prepended):
00010000a065bf68
07cb3d90d10394a9
a56693e07087ad35
24f8e303931d4ade
946dc447

Zone identifier (zid):
00010000d06ab6d9
14e8a8064609b2b3
cb661c586042adcb
0dc5faeb61994d25
5ebdca72

Encoded zone identifier (zkl = zTLD):
000G006GDAVDJ578N034C2DJPF5PC72RC11AVJRDRQXEPRCS9MJNXFEAE8

Difficulty (5 base difficulty + 2 epochs): 7

Proof:
0005b13f536e2b0e
0000395d1827c000
5caaeaa2b955d82c
5caaeaa2b955da02
5caaeaa2b955daf0
5caaeaa2b955db20
5caaeaa2b955db2d
5caaeaa2b955dba1
5caaeaa2b955dba9
5caaeaa2b955dbc2
5caaeaa2b955dbc8
5caaeaa2b955dbd1
5caaeaa2b955dbf7
5caaeaa2b955dc0e
5caaeaa2b955dc54
5caaeaa2b955dc8c
5caaeaa2b955dca5
5caaeaa2b955dcb5
5caaeaa2b955dcf8
5caaeaa2b955dd47
5caaeaa2b955dd91
5caaeaa2b955dd98
5caaeaa2b955dd99
5caaeaa2b955ddc4
5caaeaa2b955de7f
5caaeaa2b955de80
5caaeaa2b955de92
5caaeaa2b955ded3
5caaeaa2b955df1a
5caaeaa2b955df77
5caaeaa2b955dfdf
5caaeaa2b955e06e
5caaeaa2b955e08d
5caaeaa2b955e0c4
00010000d06ab6d9
14e8a8064609b2b3
cb661c586042adcb
0dc5faeb61994d25
5ebdca7206b11f93
41f4e1649976c421
b1efe668a44becbe
5a9f76804adb6f6e
2cd16de00d81841d
cbd135aacad3bdab
3f2209bd10d55cc1
c7aed9a9bd53a1f6
cae1789d

14. Normative References

[RFC1034]
Mockapetris, P., "Domain names - concepts and facilities", STD 13, RFC 1034, DOI 10.17487/RFC1034, , <https://www.rfc-editor.org/info/rfc1034>.
[RFC1035]
Mockapetris, P., "Domain names - implementation and specification", STD 13, RFC 1035, DOI 10.17487/RFC1035, , <https://www.rfc-editor.org/info/rfc1035>.
[RFC2782]
Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for specifying the location of services (DNS SRV)", RFC 2782, DOI 10.17487/RFC2782, , <https://www.rfc-editor.org/info/rfc2782>.
[RFC2119]
Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <https://www.rfc-editor.org/info/rfc2119>.
[RFC3629]
Yergeau, F., "UTF-8, a transformation format of ISO 10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, , <https://www.rfc-editor.org/info/rfc3629>.
[RFC3686]
Housley, R., "Using Advanced Encryption Standard (AES) Counter Mode With IPsec Encapsulating Security Payload (ESP)", RFC 3686, DOI 10.17487/RFC3686, , <https://www.rfc-editor.org/info/rfc3686>.
[RFC3826]
Blumenthal, U., Maino, F., and K. McCloghrie, "The Advanced Encryption Standard (AES) Cipher Algorithm in the SNMP User-based Security Model", RFC 3826, DOI 10.17487/RFC3826, , <https://www.rfc-editor.org/info/rfc3826>.
[RFC3912]
Daigle, L., "WHOIS Protocol Specification", RFC 3912, DOI 10.17487/RFC3912, , <https://www.rfc-editor.org/info/rfc3912>.
[RFC4648]
Josefsson, S., "The Base16, Base32, and Base64 Data Encodings", RFC 4648, DOI 10.17487/RFC4648, , <https://www.rfc-editor.org/info/rfc4648>.
[RFC5869]
Krawczyk, H. and P. Eronen, "HMAC-based Extract-and-Expand Key Derivation Function (HKDF)", RFC 5869, DOI 10.17487/RFC5869, , <https://www.rfc-editor.org/info/rfc5869>.
[RFC5890]
Klensin, J., "Internationalized Domain Names for Applications (IDNA): Definitions and Document Framework", RFC 5890, DOI 10.17487/RFC5890, , <https://www.rfc-editor.org/info/rfc5890>.
[RFC5891]
Klensin, J., "Internationalized Domain Names in Applications (IDNA): Protocol", RFC 5891, DOI 10.17487/RFC5891, , <https://www.rfc-editor.org/info/rfc5891>.
[RFC6781]
Kolkman, O., Mekking, W., and R. Gieben, "DNSSEC Operational Practices, Version 2", RFC 6781, DOI 10.17487/RFC6781, , <https://www.rfc-editor.org/info/rfc6781>.
[RFC6895]
Eastlake 3rd, D., "Domain Name System (DNS) IANA Considerations", BCP 42, RFC 6895, DOI 10.17487/RFC6895, , <https://www.rfc-editor.org/info/rfc6895>.
[RFC6979]
Pornin, T., "Deterministic Usage of the Digital Signature Algorithm (DSA) and Elliptic Curve Digital Signature Algorithm (ECDSA)", RFC 6979, DOI 10.17487/RFC6979, , <https://www.rfc-editor.org/info/rfc6979>.
[RFC7539]
Nir, Y. and A. Langley, "ChaCha20 and Poly1305 for IETF Protocols", RFC 7539, DOI 10.17487/RFC7539, , <https://www.rfc-editor.org/info/rfc7539>.
[RFC7748]
Langley, A., Hamburg, M., and S. Turner, "Elliptic Curves for Security", RFC 7748, DOI 10.17487/RFC7748, , <https://www.rfc-editor.org/info/rfc7748>.
[RFC8032]
Josefsson, S. and I. Liusvaara, "Edwards-Curve Digital Signature Algorithm (EdDSA)", RFC 8032, DOI 10.17487/RFC8032, , <https://www.rfc-editor.org/info/rfc8032>.
[RFC8126]
Cotton, M., Leiba, B., and T. Narten, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 8126, DOI 10.17487/RFC8126, , <https://www.rfc-editor.org/info/rfc8126>.
[GANA]
GNUnet e.V., "GNUnet Assigned Numbers Authority (GANA)", , <https://gana.gnunet.org/>.
[GNS]
Wachs, M., Schanzenbach, M., and C. Grothoff, "A Censorship-Resistant, Privacy-Enhancing and Fully Decentralized Name System", , <https://doi.org/10.1007/978-3-319-12280-9_9>.
[R5N]
Evans, N. S. and C. Grothoff, "R5N: Randomized recursive routing for restricted-route networks", , <https://doi.org/10.1109/ICNSS.2011.6060022>.
[Argon2]
Biryukov, A., Dinu, D., Khovratovich, D., and S. Josefsson, "The memory-hard Argon2 password hash and proof-of-work function", , <https://datatracker.ietf.org/doc/draft-irtf-cfrg-argon2/>.
[MODES]
Dworkin, M., "Recommendation for Block Cipher Modes of Operation: Methods and Techniques", , <https://doi.org/10.6028/NIST.SP.800-38A>.
[CrockfordB32]
Douglas, D., "Base32", , <https://www.crockford.com/base32.html>.
[Tor224]
Goulet, D., Kadianakis, G., and N. Mathewson, "Next-Generation Hidden Services in Tor", , <https://gitweb.torproject.org/torspec.git/tree/proposals/224-rend-spec-ng.txt#n2135>.
[ed25519]
Bernstein, D., Duif, N., Lange, T., Schwabe, P., and B. Yang, "High-Speed High-Security Signatures", , <http://link.springer.com/chapter/10.1007/978-3-642-23951-9_9>.

Authors' Addresses

Martin Schanzenbach
GNUnet e.V.
Boltzmannstrasse 3
85748 Garching
Germany
Christian Grothoff
Berner Fachhochschule
Hoeheweg 80
CH-2501 Biel/Bienne
Switzerland
Bernd Fix
GNUnet e.V.
Boltzmannstrasse 3
85748 Garching
Germany