ENUM B. Timms
Internet-Draft J. Reid
Intended status: Experimental Telnic
Expires: January 13, 2009 J. Schlyter
Kirei AB
July 12, 2008
IANA Registration for Encrypted ENUM
<draft-timms-encrypt-naptr-01.txt>
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Abstract
This document requests IANA registration of the "X-Crypto"
Enumservice. This Enumservice indicates that its NAPTR holds a
Uniform Resource Identifier that carries encrypted content from the
fields of another (unpublished) Protected NAPTR, for use in E.164
Number Mapping (ENUM).
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. The problem . . . . . . . . . . . . . . . . . . . . . . . 3
1.1.1. The requirements . . . . . . . . . . . . . . . . . . . 3
1.2. The solution . . . . . . . . . . . . . . . . . . . . . . . 4
1.2.1. Protected fields . . . . . . . . . . . . . . . . . . . 4
1.2.2. Protection process . . . . . . . . . . . . . . . . . . 5
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Enumservice Registration - X-Crypto . . . . . . . . . . . . . 7
4. Functional Specification . . . . . . . . . . . . . . . . . . . 8
4.1. Order . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.2. Preference . . . . . . . . . . . . . . . . . . . . . . . . 8
4.3. Services . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.4. Regexp . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.5. Replacement . . . . . . . . . . . . . . . . . . . . . . . 8
4.6. Encrypted Payload Generation . . . . . . . . . . . . . . . 9
5. Ciphersuite Subtypes . . . . . . . . . . . . . . . . . . . . . 10
5.1. Crypto Algorithms . . . . . . . . . . . . . . . . . . . . 10
5.2. Padding . . . . . . . . . . . . . . . . . . . . . . . . . 10
5.3. Hash . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
6.1. Terminal NAPTR Example . . . . . . . . . . . . . . . . . . 13
6.2. Non-Terminal NAPTR Example . . . . . . . . . . . . . . . . 14
7. Security Considerations . . . . . . . . . . . . . . . . . . . 15
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 18
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 19
10.1. Normative References . . . . . . . . . . . . . . . . . . . 19
10.2. Informative References . . . . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 20
Intellectual Property and Copyright Statements . . . . . . . . . . 21
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1. Introduction
1.1. The problem
The Domain Name System or DNS ([RFC1034],[RFC1035]) is a global
system; it does not differentiate on the data it returns. If a
Naming Authority Pointer (NAPTR) resource record [RFC3403] is
published in DNS, then by definition the same Resource Record Set
(RRset) will be returned in response to a query, regardless of the
user placing that query.
Where Universal Resource Indicators (URIs, defined in [RFC3986]) are
published within DNS (inside NAPTRs), the registrant may prefer to
make these available only to groups of individuals that he or she has
selected. Given the global nature of DNS, this can be a problem.
It is not reliably possible to return different RRset content to
different queries, depending on the user making the request. Even if
the authoritative server has been configured to discriminate based on
the source of the query, if there are any intermediary recursive
resolvers, the query may not even be passed to the authoritative
server and the response returned to the querying DNS client may not
be as the authoritative server would have chosen. It can also be
challenging to configure and maintain the authoritative server, and
this may also involve special configuration of each client that will
query for and use the data.
1.1.1. The requirements
There should be no need to use any special configuration for the
authoritative name servers, clients, or any intermediary recursive
resolvers when using this scheme. Also, there should be no special
DNS processing for the resource records used in any DNS components.
As a secondary requirement that follows from these, the same content
should be published in DNS and so made available to all without
discrimination. This will match the distributed design of the DNS
and maintain the effectiveness of the cacheing architecture.
However, the value of chosen content should be protected in such a
way that it is understandable only by a selected set of users.
There should be no performance impact on those clients that choose
not to process protected data. Thus it is important that the
recipient of this data can detect immediately that it is protected,
and either process it to extract the protected content using its
private knowledge, or immediately discard the data if it is not
interested in such protected records.
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1.2. The solution
A general solution for all DNS resource records that meets these
requirements is very difficult; the performance requirements for DNS
in general are severe. NAPTRs stored in ENUM [RFC3761] domains may
contain personally identifying information, so finding a solution may
be considered more pressing for such NAPTRs, and some restrictions or
processing costs may therefore be acceptable. Also, in the case of
NAPTRs a solution may be possible, as the problem is more restricted.
NAPTRs hold a small number of well defined fields. Not all of these
fields in a NAPTR will be sensitive and so require protection.
Those fields to be protected can be encrypted using a key known to
the intended users. Thus a "Protected" NAPTR can be processed into
two parts; the protected fields carried in a ciphertext, and the
public fields. A "Container" NAPTR can itself be used to carry this
ciphertext (inside its Regexp field content, in a URI), along with
those fields that are considered public and are not protected. These
public fields can be copied from the Protected NAPTR into this
Container NAPTR.
The Container NAPTR can be stored and retrieved in the normal way.
It will have an Enumservice indicating that it acts as a container
and MUST be decoded before the original Protected NAPTR can be
reconstructed and processed. When an ENUM client retrieves such a
Container NAPTR, it can immediately know that this requires
cryptographic processing, and if that client is not interested in
such processing, the NAPTR can be discarded.
1.2.1. Protected fields
There is no great benefit to encrypting all of the RDATA (Resource
record Data) for a NAPTR. The ORDER and PREFERENCE/PRIORITY fields
are used to indicate the preferred order in which the records within
a returned NAPTR RRset will be processed. Whether a particular NAPTR
acts as a container for a Protected NAPTR's content or not, the order
in which it will be processed should remain the same; there is no
change to the Dynamic Delegation Discovery System (DDDS) algorithm
specified in [RFC3402].
If instead the Container NAPTR had a different ORDER and PREFERENCE/
PRIORITY field values from those held in the Protected NAPTR, it
might be possible for a Container NAPTR to be considered first (as it
had a low numerical order/preference value), but, once decoded, the
Protected NAPTR content it contained was of a much lower priority,
and so should not be processed at that point. This would be
inappropriate, and so the ORDER and PREFERENCE/PRIORITY fields will
remain the same in both Protected and Container NAPTRs.
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Thus the ORDER and PREFERENCE/PRIORITY field values should be
considered public and be copied from the Protected NAPTR into the
Container NAPTR. However, all the other fields (flags, services,
regexp, and replacement) are sensitive in nature, and so that portion
of the binary format of the RDATA in which they are held will form
the plaintext that will be protected before publication in DNS.
1.2.2. Protection process
The NAPTR to be protected can have these sensitive fields placed into
a plaintext buffer. The buffer content is then encrypted using an
appropriate key to create a ciphertext. The ciphertext can then be
"armoured" into a form that can be presented in a data URI [RFC2397].
That URI can then be placed in a Container NAPTR within its Regexp
field, along with the "public" ORDER and PREFERENCE/PRIORITY fields
copied from the Protected NAPTR, together with a dedicated
Enumservice, terminal URI flag field ('u') and an empty Replacement
field.
If this Container NAPTR has an appropriate Enumservice then its
nature will be immediately detectable by the recipient of that NAPTR.
If the recipient has the appropriate key to decode the URI data, then
it can decrypt the URI content to form a buffer with the plaintext
fields. These fields (in combination with the ORDER and PREFERENCE/
PRIORITY fields that have been copied into the Container NAPTR and
have not been encoded) can be reconstructed into the RDATA that would
have existed in the original Protected NAPTR. That Protected NAPTR
content can then be processed by the client in the normal way.
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2. Terminology
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].
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3. Enumservice Registration - X-Crypto
The following template contains information required for the IANA
registrations of the 'X-Crypto' Enumservice, according to Section 3
of RFC 3761:
Enumservice Name: "X-Crypto"
Enumservice Type: "x-crypto"
Enumservice Subtype: "data"
Enumservice Sub-subtype: see Section 5
URI Schemes: "data"
Functional Specification: see Section 4
Security Specification: see Section 7
Intended Usage: COMMON
Author(s): Ben Timms, Jim Reid, Jakob Schlyter. (for authors contact
details see Authors' Addresses section).
Any other information that the author deems interesting: None
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4. Functional Specification
The basic concept is covered in Section 1.2 and the process is
covered in Section 1.2.2. This section describes in detail how each
of the fields are handled.
Publication and use of a NAPTR with this Enumservice is based on two
concepts:
A Protected NAPTR that contains sensitive field values, and is not
stored and published in DNS.
A Container NAPTR with this Enumservice that holds the protected
fields in encrypted form within its Regexp field. This NAPTR
carries the "x-crypto" Enumservice
The Container NAPTR resource record fields are as follows:
4.1. Order
The value of the order field is copied in clear from the RDATA of the
Protected NAPTR into the Container NAPTR. It is not encoded.
4.2. Preference
The value of the preference field is copied in clear from the RDATA
of the Protected NAPTR to the Container NAPTR. It is not encoded.
4.3. Services
The value of the services field for the Container NAPTR is set to
"E2U+x-crypto:data:" combined with the ciphersuite sub-subtype
(Section 5).
4.4. Regexp
The encrypted payload (Section 4.6) is encoded in Base64 [RFC4648],
and transported as the value of a data URI [RFC2397] inside the
Container NAPTR.
Container NAPTR Regexp Example:
!^.*$!data:;base64,bWVrbWl0YXNkaWdvYXQK!
4.5. Replacement
The value of the Container NAPTR's replacement field MUST be set to
".".
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4.6. Encrypted Payload Generation
The Encrypted Payload consists of a base64 "armoured" string holding
an encrypted, optionally padded ciphertext reflecting a portion of
the Protected NAPTR's RDATA.
The portion of the Protected NAPTR RDATA holding its Flags, Services,
Regexp and Replacement fields is treated as the plaintext to be
processed. This plaintext is (optionally) padded and the resulting
block is then encrypted, to form the ciphertext. Potentially, an
optional hash may be generated from this. Once this cipehertext has
been generated, it is further encoded in Base64 to form the encrypted
payload that is then used as the value of the Container NAPTR's URI.
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5. Ciphersuite Subtypes
The enumservice sub-subtype carries the ciphersuite used for the
encrypted payload.
Ciphersuite sub-subtype example: RSA 1024-bit with PKCS#1.5 padding
and no hash would be encoded as 0x8210 and presented as enumservice
"E2U+x-crypto:data:8210".
5.1. Crypto Algorithms
A 1-byte field indicating the encryption algorithm is used for the
encrypted payload (Section 4.6).
+-------+----------------------+
| Value | Encryption Algorithm |
+-------+----------------------+
| 0x00 | NULL |
| | |
| 0x81 | RSA-512 |
| | |
| 0x82 | RSA-1024 |
| | |
| 0x83 | RSA-1536 |
| | |
| 0x84 | RSA-2048 |
| | |
| 0x85 | RSA-3072 |
| | |
| 0x86 | RSA-4096 |
+-------+----------------------+
5.2. Padding
A 4-bit field indicating what padding algorithm is used for the
encrypted payload (Section 4.6).
+-------+-------------------+
| Value | Padding Algorithm |
+-------+-------------------+
| 0x0 | NULL |
| | |
| 0x1 | PKCS #1.5 |
| | |
| 0x2 | OAEP |
+-------+-------------------+
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5.3. Hash
A 4-bit field indicating what hash algorithm is used for the
encrypted payload (Section 4.6).
+-------+----------------+
| Value | Hash Algorithm |
+-------+----------------+
| 0x0 | NULL |
| | |
| 0x1 | MD2 |
| | |
| 0x2 | MD5 |
| | |
| 0x3 | SHA-1 |
| | |
| 0x4 | SHA-224 |
| | |
| 0x5 | SHA-256 |
| | |
| 0x6 | SHA-384 |
| | |
| 0x7 | SHA-512 |
+-------+----------------+
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6. Examples
In these examples, a 1024-bit RSA key pair is used for encryption and
decryption. The plaintext has cryptographic padding applied prior to
encryption, using the PKCS 1.5 algorithm. There is a null hash
applied to this. The ciphersuite value (i.e. the Enumservice sub-
sub-type string held in the container NAPTR) will be '8210'. The
resultant ciphertext is further "armoured" using Base 64 encoding,
and is placed into a data URI in that container NAPTR. A "default"
or "greedy" Extended Regular Expression, or ERE (i.e. '!^.*$!') is
used in the container NAPTR Regexp field. Note that (in keeping with
[RFC4648], section 3.1), the "aromouring" process MUST NOT add line
feeds to the base-encoded data.
For ease of presentation the examples are shown in textual form, but
the encryption process works on the binary form of the RDATA fields.
Note that, using this encryption, encoding and ERE mechanism, the
limit to the length of the "plaintext" (i.e. the fields of the RDATA
to be protected) is 117 bytes. This is because RSA is a block
cipher, with in this case 1024 bits (128 bytes) as the block size,
and the PKCS #1.5 padding to be added to the plaintext consumes 11
bytes, leaving a maximum plaintext size of 117 bytes.
Once encrypted, the ciphertext is also 128 bytes, but this is in
binary form, and has to be further "armoured" for carriage inside the
data: URI. The Base 64 encoding process expands the ciphertext to
4/3 (rounded up to the nearest 4 bytes) of its size in binary form,
giving a text block of 172 bytes. To this has to be added the rest
of the container NAPTR's Regexp content, giving a Regexp field length
of 193 bytes. Note that this field length is constant, as the
ciphertext is always the same length when using the same encryption
and padding scheme (regardless of the length of the plaintext fields
to be protected and whether these fields reflect a terminal or non-
terminal NAPTR).
In the following examples, it is assumed that the private key (in
PKCS 8 format, protected with the pass phrase "pkcs8passphrase", and
expressed in PEM format), is:
-----BEGIN ENCRYPTED PRIVATE KEY-----
MIICoTAbBgkqhkiG9w0BBQMwDgQIpwb76GrK0AgCAggABIICgEsRtkQ2isuKq3Cl
8wpAfDxzzFbumj0HdGu7WLEElVYaLt4CvRlz5kL3SK2G8ydpsdU104s0RnzgPGFv
63zsJZ5bC6d4lCcWMjbhv+U91YUhlrc6R6UHhIN4BSBWTeA/Ia/U7bwZm/TV7ke1
eeLOdsyzEnPr9lj3v1wdHFYU6CMY1lRP/lbqexVQMYEev5/w+tu9LyGdP3MPnnUC
N/OVk67OkwBqrBnQpHtHLC7i0bq6srLaJWB7nFVa/iXlQ8lCwFRGwV7RDq6JvgI2
LjgJArLG8i7QBx+WE/+LwLAessmU4RUzzvQhnlWdf3UkXR/hRDPRhJFFrr5zjfUr
cF5CfZms4WhMh+epqnlaoaX7uEj1gQ9gLvNef3b68akpRVIFuLBnqcdbahr0rzQA
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/LT5e62jfo2saSG9vVAY7f1fOmrh9K9+S69rlbQ4JLzx+sttPTty9CscIZf3/cDM
1GNdumwG1HewzkVuzvIlyJfLbM1ftWhv0tWTe8pPFqccTFYvwpjVnOxN6yr8EMUy
8VTyDCZT/us8E6vtei2fbvLHnmRzIqCgHUAYBVKM+cwrGELCuSBbx6pmOp21EyGH
5+Lobg0XYjArVxgynNvAU/mmQWbdVqhkfrIGhywCvi1+Jpigvn+2zBayCfPitdxh
BjvYhEp6qSE0/QWog4Qn6t5TaDK7ddV39Tw2pyuE1Gh+tAfZWrwO0aF9NKI9G5mJ
Db3Jqm9UzAoulH8cnMdCAa7oDVCl/8ky1VKTIz8fe3bVsMCm8Cgv3/vz8vupaGV5
exzJUEeEJweenReOaI8Eocl2qSKmcrtlhAQI+l77KnvM3J0QSPSxeH203OnLovG3
lQkJjd4=
-----END ENCRYPTED PRIVATE KEY-----
The public key, expressed in PEM format, is:
-----BEGIN PUBLIC KEY-----
MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDoOyVQpfJlai3i7RlF5iGGlYUb
/HXOuyV1IVKoQ1iQQvm91gU5L10GwVWN1WY4yfqYtPXnJMoMbAIK72wNnaB6Jo4/
ELbi40yOQSIe4TKXVcfMkFbpJlN7FfktHtpLai60zsT8Ywt4OF8rUFmb5CdE3gtV
yqQfmfczYheXqPW7iwIDAQAB
-----END PUBLIC KEY-----
6.1. Terminal NAPTR Example
This example shows a NAPTR holding a SIP Enumservice as the protected
NAPTR. Given that a terminal E2U (ENUM) NAPTR is to be protected,
the combined maximum length of the Enumservice string, the ERE
pattern and the original URI is (117 - 12) bytes, or 105 bytes. If a
"greedy" ERE field is used in that protected NAPTR, the space
available for the Enumservice string and the URI is 105 - 4 bytes, or
101 bytes. In the example shown here, the NAPTR to be protected has
a SIP Enumservice (and corresponding sip: URI scheme). This means
that the SIP address value can be a maximum of 94 bytes long. In
this case, it occuplies 24 bytes.
The protected NAPTR RDATA:
100 50 'u' 'E2U+sip' '!^.*$!sip:alice@wonderland.example!' .
Is replaced by the container NAPTR RDATA:
100 50 'u' 'E2U+X-crypto:data:8210'
'!^.*$!data:;base64,OQZl3x9TEaZtQamA5t3IJqXaKUT6QuV+yLtW34/hszd
D2jtSwavlxiax8CDMWekikXkgbPQqEo7X6g8aX3REiXVJ/PqrbxFASIIktnIIVE
rZU3RVl8WAvxQvWGs+wEY3YAi4UnOoqAOdbv3tsV0i4h15I+wePz9Rw9VBpU95h
Wc=!' .
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6.2. Non-Terminal NAPTR Example
In this example, a non-terminal NAPTR is protected. As the
replacement field in a NAPTR is not permitted (as specified in RFC
3403) to use DNS domain compression, the fully qualified domain name
of the target domain is held in the replacement field. This fully
qualified domain name is, of course, stored in binary form within the
RDATA.
Note that, using the same protection scheme (1024-bit RSA, with PKCS
1.5 padding, null hash), the maximum length of the fully qualified
domain name will be 117 - 3, or 114 bytes. In this example, the
fully qualified domain name is 1+5+1+10+1+7+1 = 26 bytes long.
The protected non-terminal NAPTR RDATA:
100 51 '' '' '' alice.wonderland.example.
Is replaced by the container NAPTR RDATA:
100 51 'u' 'e2u+x-crypto:data:8210'
'!^.*$!data:;base64,j+WNPPwriy5pu4SfabMavRtE+c/f3Sk62Ab5TNYOomo
RcGrKk5q23i6BB4fp71+z3ezK1U91jTdpzmpF0M7WVs9M9AnhDxyrbQwo1mP/uU
YpflaZuG5aEnY14aTntAldh7UacPvfaiWc1QPg/6C9Wb7MBedmZAYajc2YZHgKQ
1o=!' .
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7. Security Considerations
This is an Enumservice for a NAPTR intended to carry protected NAPTR
content in encrypted form. It does not discuss the means by which
the keys needed to decrypt the protected content are exchanged. For
this Enumservice registration, this is considered "out of scope".
However, the technique used for key exchange is important, and must
be considered thoroughly; there is little point in applying a complex
encryption scheme if the keys are available to eavesdroppers. Of
course, although technically permitted, confidentiality will not be
achieved unless a non-null encryption is applied.
There are limitations on field size within DNS, so that, for example,
the Regexp field has a maximum length of 255 bytes. Several of these
bytes will be taken up in the container NAPTR's Regexp field with the
sub-field delimiters, with the ERE sub-field content, and with the
URI scheme itself. There is limited space to carry the armoured
ciphertext as the data URI value, given the armouring choice proposed
here and the simple use of the existing Regexp field to carry the
protected data. This will in turn limit the choices for encryption
method, hash algorithm, and any padding. See also the examples
above.
Even if an eavesdropper cannot decode the content carried in a
container NAPTR, the fact that ORDER and PREFERENCE/PRIORITY fields
are copied from the protected NAPTR opens the possibility of opaque
traffic analysis. If the ORDER and PREFERENCE/PRIORITY field values
for a NAPTR within a RRSet change (for example, to reflect the domain
owner going from office to home) then this change will be reflected
in the NAPTR even if it is protected. Simply due to changes in RRSet
relative ORDER and PREFERENCE/PRIORITY values, an attacker might
surmise that the protected data was associated with the domain
owner's office or home number. This information might in itself be
useful to the attacker (for example, by indicating when the domain
owner was or was not present at a particular location).
Finally, if the value of a contact (such as a SIP URI or telephone
number) were to be available to an attacker using other means, then
there may be potential for differential cryptographic analysis based
on an assumed "known plaintext". The amount of data available to an
attacker with realistic numbers of NAPTRs is small, but it is
important to use appropriate cryptographic padding to limit the
potential for such an attack.
These issues mean that the environment in which NAPTRs with this
Enumservice can be used may be restricted, and further security
analysis will depend on deployment experience.
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An analysis of threats specific to the dependence of ENUM on the DNS,
and the applicability of DNSSEC ("Domain Name Security") [RFC4035] to
these, is provided in [RFC3833].
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8. IANA Considerations
This document requests registration of the "X-Crypto" Enumservice
with the "x-crypto:data:<ciphersuite>" type according to the
guidelines and specifications in RFC 3761 [RFC3761] and the
definitions in this document. This Enumservice is intended for use
with the "data:" URI scheme.
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9. Acknowledgements
The authors gratefully acknowledge the contributions of Romek
Szczesniak. He helped greatly to clarify some of the issues with
deployed security schemes and current implementations. We also
acknowledge the support of Khashayar Mahdavi whose original idea this
draft embodies, and Henri Asseily for driving the development of the
environment in which this is being used.
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10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2397] Masinter, L., "The "data" URL scheme", RFC 2397,
August 1998.
[RFC3402] Mealling, M., "Dynamic Delegation Discovery System (DDDS)
Part Two: The Algorithm", RFC 3402, October 2002.
[RFC3403] Mealling, M., "Dynamic Delegation Discovery System (DDDS)
Part Three: The Domain Name System (DNS) Database",
RFC 3403, October 2002.
[RFC3761] Faltstrom, P. and M. Mealling, "The E.164 to Uniform
Resource Identifiers (URI) Dynamic Delegation Discovery
System (DDDS) Application (ENUM)", RFC 3761, April 2004.
[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, October 2006.
10.2. Informative References
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, November 1987.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987.
[RFC3833] Atkins, D. and R. Austein, "Threat Analysis of the Domain
Name System (DNS)", RFC 3833, August 2004.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005.
[RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Protocol Modifications for the DNS Security
Extensions", RFC 4035, March 2005.
Timms, et al. Expires January 13, 2009 [Page 19]
Internet-Draft ENUM Encryption July 2008
Authors' Addresses
Ben Timms
Telnic
37 Percy Street
London W1T 2DJ
United Kingdom
Email: btimms@telnic.org
Jim Reid
Telnic
37 Percy Street
London W1T 2DJ
United Kingdom
Email: jim@telnic.org
Jakob Schlyter
Kirei AB
P.O. Box 53204
Goteborg SE-400 16
Sweden
Email: jakob@kirei.se
Timms, et al. Expires January 13, 2009 [Page 20]
Internet-Draft ENUM Encryption July 2008
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Timms, et al. Expires January 13, 2009 [Page 21]