Internet DRAFT - draft-ietf-rmt-simple-auth-for-alc-norm
draft-ietf-rmt-simple-auth-for-alc-norm
RMT V. Roca
Internet-Draft INRIA
Intended status: Standards Track December 9, 2011
Expires: June 11, 2012
Simple Authentication Schemes for the ALC and NORM Protocols
draft-ietf-rmt-simple-auth-for-alc-norm-06
Abstract
This document introduces four schemes that provide per-packet
authentication, integrity and anti-replay services in the context of
the ALC and NORM protocols. The first scheme is based on RSA digital
signatures. The second scheme relies on the Elliptic Curve Digital
Signature Algorithm (ECDSA). The third scheme relies on a group-
keyed Message Authentication Code (MAC). Finally, the fourth scheme
merges the digital signature and group schemes. These schemes have
different target use cases and they do not all provide the same
service.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on June 11, 2012.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
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to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1. Scope of this Document . . . . . . . . . . . . . . . . . . 7
1.2. Terminology, Notations and Definitions . . . . . . . . . . 7
2. Authentication Scheme Identification with the ASID Field . . . 9
3. RSA Digital Signature Scheme . . . . . . . . . . . . . . . . . 10
3.1. Authentication Header Extension Format . . . . . . . . . . 10
3.2. Parameters . . . . . . . . . . . . . . . . . . . . . . . . 11
3.3. Processing . . . . . . . . . . . . . . . . . . . . . . . . 12
3.3.1. Signature Processing . . . . . . . . . . . . . . . . . 12
3.3.2. Anti-Replay Processing . . . . . . . . . . . . . . . . 13
3.4. In Practice . . . . . . . . . . . . . . . . . . . . . . . 14
4. Elliptic Curve Digital Signature Scheme . . . . . . . . . . . 15
4.1. Authentication Header Extension Format . . . . . . . . . . 15
4.2. Parameters . . . . . . . . . . . . . . . . . . . . . . . . 16
4.3. Processing . . . . . . . . . . . . . . . . . . . . . . . . 16
4.3.1. Signature Processing . . . . . . . . . . . . . . . . . 16
4.3.2. Anti-Replay Processing . . . . . . . . . . . . . . . . 17
4.4. In Practice . . . . . . . . . . . . . . . . . . . . . . . 17
5. Group-Keyed Message Authentication Code (MAC) Scheme . . . . . 19
5.1. Authentication Header Extension Format . . . . . . . . . . 19
5.2. Parameters . . . . . . . . . . . . . . . . . . . . . . . . 20
5.3. Processing . . . . . . . . . . . . . . . . . . . . . . . . 21
5.3.1. Signature Processing . . . . . . . . . . . . . . . . . 21
5.3.2. Anti-Replay Processing . . . . . . . . . . . . . . . . 21
5.4. In Practice . . . . . . . . . . . . . . . . . . . . . . . 21
6. Combined Use of the RSA/ECC Digital Signatures and
group-keyed MAC Schemes . . . . . . . . . . . . . . . . . . . 23
6.1. Authentication Header Extension Format . . . . . . . . . . 23
6.2. Parameters . . . . . . . . . . . . . . . . . . . . . . . . 24
6.3. Processing . . . . . . . . . . . . . . . . . . . . . . . . 24
6.3.1. Signature Processing . . . . . . . . . . . . . . . . . 24
6.3.2. Anti-Replay Processing . . . . . . . . . . . . . . . . 25
6.4. In Practice . . . . . . . . . . . . . . . . . . . . . . . 25
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27
8. Security Considerations . . . . . . . . . . . . . . . . . . . 28
8.1. Dealing With DoS Attacks . . . . . . . . . . . . . . . . . 28
8.2. Dealing With Replay Attacks . . . . . . . . . . . . . . . 28
8.2.1. Impacts of Replay Attacks on the Simple
Authentication Schemes . . . . . . . . . . . . . . . . 28
8.2.2. Impacts of Replay Attacks on NORM . . . . . . . . . . 28
8.2.3. Impacts of Replay Attacks on ALC . . . . . . . . . . . 29
8.3. Dealing With Attacks on the Parameters Sent Out-of-Band . 30
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 31
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 32
10.1. Normative References . . . . . . . . . . . . . . . . . . . 32
10.2. Informative References . . . . . . . . . . . . . . . . . . 32
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Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 34
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1. Introduction
Many applications using multicast and broadcast communications
require that each receiver be able to authenticate the source of any
packet it receives to check its integrity. For instance, ALC
[RFC5775] and NORM [RFC5740] are two Content Delivery Protocols (CDP)
designed to reliably transfer objects (e.g. files) between a
session's sender and several receivers.
The NORM protocol is based on bidirectional transmissions. With NORM
each receiver acknowledges data received or, in case of packet
erasures, asks for retransmissions. On the opposite, the ALC
protocol defines unidirectional transmissions. With ALC, reliability
can be achieved by means of cyclic transmissions of the content
within a carousel, or by the use of proactive Forward Error
Correction codes (FEC), or by the joint use of these mechanisms.
Being purely unidirectional, ALC is massively scalable, while NORM is
intrinsically limited in terms of the number of receivers that can be
handled in a session. Both protocols have in common the fact that
they operate at application level, on top of an erasure channel (e.g.
the Internet) where packets can be lost (erased) during the
transmission.
With these CDP, an attacker might impersonate the ALC or NORM session
sender and inject forged packets to the receivers, thereby corrupting
the objects reconstructed by the receivers. An attacker might also
impersonate a NORM session receiver and inject forged feedback
packets to the NORM sender.
In case of group communications, several solutions exist to provide
the receiver some guaranties on the integrity of the packets it
receives and on the identity of the sender of these packets. These
solutions have different features that make them more or less suited
to a given use case:
o digital signatures [RFC4359] (see Section 3 and Section 4): this
scheme is well suited to low data rate flows, when a packet sender
authentication and packet integrity service is needed. However,
digital signatures based on RSA asymmetric cryptography are
limited by high computational costs and high transmission
overheads. The use of ECC ("Elliptic Curve Cryptography")
[RFC6090] significantly relaxes these constraints. For instance,
the following key lengths provide equivalent security: 1024 bit
RSA key versus 160 bit ECC key, or 2048 bit RSA key versus 224 bit
ECC key. However RSA puts more load on the signer but much much
less on the verifier, whereas ECC puts more similar load on both
and hence with many verifiers more CPU is consumed overall.
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o group-keyed Message Authentication Codes (MAC) (see Section 5):
this scheme is well suited to high data rate flows, when
transmission overheads must be minimized. However this scheme
cannot protect against attacks coming from inside the group, where
a group member impersonates the sender and sends forged messages
to other receivers.
o TESLA (Timed Efficient Stream Loss-tolerant Authentication)
[RFC4082][RFC5776]: this scheme is well suited to high data rate
flows, when transmission overheads must be minimized, and when a
packet sender authentication and packet integrity service is
needed. The price to pay is an increased complexity, in
particular the need to loosely synchronize the receivers and the
sender, as well as the need to wait for the key to be disclosed
before being able to authenticate a packet (i.e. the
authentication check is delayed)
The following table summarizes the pros/cons of each authentication/
integrity scheme used at application/transport level (where "-" means
bad, "0" means neutral, and "+" means good):
+-----------------+-------------+-------------+-------------+-------+
| | RSA Digital | ECC Digital | Group-Keyed | TESLA |
| | Signature | Signature | MAC | |
+-----------------+-------------+-------------+-------------+-------+
| Sender auth and | Yes | Yes | No (group | Yes |
| packet | | | security) | |
| integrity | | | | |
| | | | | |
| Non delayed | Yes | Yes | Yes | No |
| authentication | | | | |
| | | | | |
| Anti-replay | Opt | Opt | Opt | No |
| protection | | | | |
| | | | | |
| Processing load | - | sender: -, | + | + |
| | | recv: 0 | | |
| | | | | |
| Transmission | - | 0 | + | + |
| overhead | | | | |
| | | | | |
| Complexity | + | + | + | - |
+-----------------+-------------+-------------+-------------+-------+
Several authentication schemes MAY be used in the same ALC or NORM
session, even on the same communication path. This is made possible
through a dedicated identifier, "ASID" (Authentication Scheme
IDentifier), that is present in each HET=1 (EXT_AUTH) header
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extension and that tells a receiver how to interpret this HET=1
header extension. This is discussed in Section 2.
All the applications built on top of ALC and NORM directly benefit
from the source authentication and packet integrity services defined
in this document. For instance this is the case of the FLUTE
application [RMT-FLUTE] built on top of ALC.
The current specification assumes that several parameters (like
keying material) are communicated out-of-band, sometimes securely,
between the sender and the receivers. This is detailed in
Section 3.2, Section 4.2, Section 5.2, and Section 6.2.
1.1. Scope of this Document
[RFC5776] explains how to use TESLA in the context of ALC and NORM
protocols.
The current document specifies the use of the Digital Signature based
on RSA asymmetric cryptography, the Elliptic Curve Digital Signature
Algorithm (ECDSA) and group-keyed MAC schemes. The current document
also specifies the joint use of Digital Signature and group-keyed MAC
schemes.
Unlike the TESLA scheme, this specification considers the
authentication/integrity of the packets generated by the session's
sender as well as those generated by the receivers (NORM).
1.2. Terminology, Notations and Definitions
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].
The following notations and definitions are used throughout this
document:
o MAC is the Message Authentication Code;
o HMAC is the Keyed-Hash Message Authentication Code;
o sender denotes the sender of a packet that needs the
authentication/integrity check service. It can be an ALC or NORM
session sender, or a NORM session receiver in case of feedback
traffic;
o receiver denotes the receiver of a packet that needs the
authentication/integrity check service. It can be an ALC or NORM
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session receiver, or a NORM session sender in case of feedback
traffic;
o ASID is the Authentication Scheme IDentifier;
Key definitions for Digital signatures:
o the public key is used by a receiver to check a packet's
signature. This key MUST be communicated to all receivers, before
starting the session;
o the private key is used by a sender to generate a packet's
signature;
o the private key and public key length are expressed in bits. For
security considerations [RFC5751], when using RSA, RSASSA-PSS, and
DSA signatures, key sizes of length strictly inferior to 1024 bits
SHOULD NOT be used. Key sizes of length between 1024 and 2048
bits, inclusive, SHOULD be used. Key sizes of length strictly
superior to 2048 MAY be used.
Keys definitions for Group-keyed MAC:
o the shared group key is used by the senders and the receivers.
This key MUST be communicated to all group members,
confidentially, before starting the session;
o the group key length is expressed in bits;
o n_m is the length of the truncated output of the MAC [RFC2104].
Only the n_m left-most bits (most significant bits) of the MAC
output are kept;
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2. Authentication Scheme Identification with the ASID Field
As mentioned in Section 1, several authentication schemes MAY be used
in the same ALC or NORM session, even on the same communication path
(i.e., from a sender to a receiver, or vice-versa). All the schemes
mentioned in Section 1 (some of them being specified in this
document) use the same HET=1 (EXT_AUTH) authentication header
extension mechanism defined in [RFC5651]. Therefore, the same 4-bit
ASID (Authentication Scheme IDentifier) field has been reserved in
all the specifications (see Section 3.1, Section 5.1, Section 6.1 and
[RFC5776], section 5.1). For a given ALC or NORM session, the ASID
value contained in an incoming packet enables a receiver to
differentiate the actual use and format of the contents of the HET=1
(EXT_AUTH) header extension.
The association between the ASID value and the actual authentication
scheme of a given ALC or NORM session is defined at session startup
and communicated to all the session members by an out-of-band
mechanism. This association is per ALC or NORM session, and
different sessions MAY reuse the same ASID values for different
authentication schemes.
With ALC, the ASID value is scoped by the {sender IP address; TSI}
tuple [RFC5651] that fully identifies an ALC session. Since
[RFC5651] requires that "the TSI MUST be unique among all sessions
served by the sender during the period when the session is active,
and for a large period of time preceding and following when the
session is active", there is no risk of confusion between different
sessions. This is in line with Section 8.2.3.
With NORM, there is no session identifier within NORM packets.
Therefore, depending on whether an Any Source Multicast (ASM) or
Source Specific Multicast (SSM) group communication is used, the ASID
value is scoped either by the {destination multicast address;
destination port number} or {source IP address; destination multicast
address; destination port number} tuple that fully identifies a NORM
session [RFC5740]. Care should be taken that the above tuples remain
unique, within a given scope and for a sufficient period of time
preceding, during and following when the session is active, to avoid
confusion between different sessions. However, this is a
recommendation for NORM sessions, rather than something specific to
an authentication scheme. Note also that the ASID value is not
scoped by the {"source_id"; "instance_id"} tuple, which uniquely
identifies a host participation in a NORM session, rather than the
session itself Section 8.2.2.
In any case, because this ASID field is 4-bit long, there is a
maximum of 16 authentication schemes per ALC or NORM session.
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3. RSA Digital Signature Scheme
3.1. Authentication Header Extension Format
The integration of Digital Signatures is similar in ALC and NORM and
relies on the header extension mechanism defined in both protocols.
More precisely this document details the HET=1 (EXT_AUTH) header
extension defined in [RFC5651].
Several fields are added in addition to the HET (Header Extension
Type) and HEL (Header Extension Length) fields (Figure 1).
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| HET (=1) | HEL | ASID | rsvd|A| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
~ anti-replay Sequence Number (SN) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ ~
| Signature |
+ +-+-+-+-+-+-+-+-+
| | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Format of the Digital Signature EXT_AUTH header extension.
The fields of the Digital Signature EXT_AUTH header extension are:
"ASID" (Authentication Scheme IDentifier) field (4 bits):
The "ASID" identifies the source authentication scheme or protocol
in use. The association between the "ASID" value and the actual
authentication scheme is defined out-of-band, at session startup.
"Reserved" field (3 bits):
This is a reserved field that MUST be set to zero and ignored by
receivers.
"A" (Anti-replay) field (1 bit):
The "AR" field, when set to 0, indicates that the anti-replay
service is not used. When set to 1, it indicates that the anti-
replay service is used.
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"SN" (Sequence Number) field (8 or 40 bits):
The "SN" field contains an optional sequence number. When AR=0,
this is an 8 bit field that MUST be set to zero. No anti-replay
mechanism is used in that case. When AR=1, this is a 32+8=40 bit
field and all of the 40 bits MUST be considered by the anti-replay
mechanism.
"Signature" field (variable size, multiple of 32 bits):
The "Signature" field contains a digital signature of the message.
If need be, this field is padded (with 0) up to a multiple of 32
bits.
3.2. Parameters
Several parameters MUST be initialized by an out-of-band mechanism.
The sender or group controller:
o MUST communicate his public key, for each receiver to be able to
verify the signature of the packets received. For security
reasons [RFC5751], the use of key sizes between 1024 and 2048
inclusive is RECOMMENDED. Key sizes inferior to 1024 SHOULD NOT
be used. Key sizes above 2048 MAY be used. As a side effect, the
receivers also know the key length and the signature length, the
two parameters being equal;
o MAY communicate a certificate (which also means that a PKI has
been setup), for each receiver to be able to check the sender's
public key;
o MUST communicate the Signature Encoding Algorithm. For instance,
[RFC3447] defines the RSASSA-PKCS1-v1_5 and RSASSA-PSS algorithms
that are usually used to that purpose;
o MUST communicate the One-way Hash Function, for instance SHA-1,
SHA-224, SHA-256, SHA-384, or SHA-512. Because of security
threats on SHA-1, the use of SHA-256 is RECOMMENDED [RFC6194];
o MUST associate a value to the "ASID" field (Authentication Scheme
IDentifier) of the EXT_AUTH header extension (Section 3.1);
o MUST communicate whether the anti-replay service is used or not
for this session;
These parameters MUST be communicated to all receivers before they
can authenticate the incoming packets. For instance it can be
communicated in the session description, or initialized in a static
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way on the receivers, or communicated by means of an appropriate
protocol. The details of this out-of-band mechanism are out of the
scope of this document.
3.3. Processing
3.3.1. Signature Processing
The computation of the digital signature, using the private key, MUST
include the ALC or NORM header (with the various header extensions)
and the payload when applicable. The UDP/IP/MAC headers MUST NOT be
included. During this computation, the "Signature" field MUST be set
to 0.
Several "Signature Encoding Algorithms" can be used, including
RSASSA-PKCS1-v1_5 and RSASSA-PSS. With these encodings, several
"One-way Hash Function" can be used, like SHA-256.
First, let us consider a packet sender. More specifically, from
[RFC4359]: digital signature generation is performed as described in
[RFC3447], Section 8.2.1 for RSASSA-PKCS1-v1_5 and Section 8.1.1 for
RSASSA-PSS. The authenticated portion of the packet is used as the
message M, which is passed to the signature generation function. The
signer's RSA private key is passed as K. In summary (when SHA-256 is
used), the signature generation process computes a SHA-256 hash of
the authenticated packet bytes, signs the SHA-256 hash using the
private key, and encodes the result with the specified RSA encoding
type. This process results in a value S, which is the digital
signature to be included in the packet.
With RSASSA-PKCS1-v1_5 and RSASSA-PSS signatures, the size of the
signature is equal to the "RSA modulus", unless the "RSA modulus" is
not a multiple of 8 bits. In that case, the signature MUST be
prepended with between 1 and 7 bits set to zero such that the
signature is a multiple of 8 bits [RFC4359]. The key length, which
in practice is also equal to the "RSA modulus", has major security
implications. [RFC4359] explains how to choose this value depending
on the maximum expected lifetime of the session. This choice is out
of the scope of this document.
Now let us consider a receiver. From [RFC4359]: Digital signature
verification is performed as described in [RFC3447], Section 8.2.2
(RSASSA-PKCS1-v1_5) and [RFC3447], Section 8.1.2 (RSASSA-PSS). Upon
receipt, the digital signature is passed to the verification function
as S. The authenticated portion of the packet is used as the message
M, and the RSA public key is passed as (n, e). In summary (when SHA-
256 is used), the verification function computes a SHA-256 hash of
the authenticated packet bytes, decrypts the SHA-256 hash in the
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packet using the sender's public key, and validates that the
appropriate encoding was applied. The two SHA-256 hashes are
compared and if they are identical the validation is successful.
3.3.2. Anti-Replay Processing
Let us assume the anti-replay service is used. The principles are
similar to the Sequence Number mechanism described in [RFC4303], with
the exception that the present document uses a 40 bit field that
contains all the bits of the sequence number counter.
At the sender, the mechanism works as follows ([RFC4303], section
2.2). The sender's sequence number counter is initialized to 0 at
session startup. The sender increments the Sequence Number counter
for this session and inserts the value into the SN field. Thus, the
first packet sent will contain a SN of 1. The SN value of the
Authentication Header Extension MUST be initialized before the
signature generation process, in order to enable a receiver to check
the SN value during the integrity verification process.
The sender SHOULD ensure that the counter does not cycle before
inserting the new value in the SN field. Failing to follow this rule
would enable an attacker to replay a packet sent during the previous
cycle, i.e., it would limit the anti-replay service to a single SN
cycle. Since the sequence number is contained in a 40 bit field, it
is expected that cycling will never happen in most situations. For
instance, on a 10 Gbps network, with small (i.e., 64 byte long)
packets, cycling will happen after slightly more than 15 hours.
At the receiver, the mechanism works as follows ([RFC4303], sections
3.4.3 and A2). For each received packet, the receiver MUST verify
that the packet contains a Sequence Number that does not duplicate
the Sequence Number of any other packets received during the session.
If this preliminary check fails, the packet is discarded, thus
avoiding the need for any cryptographic operations by the receiver.
If the preliminary check is successful, the receiver cannot yet
modify its local counter, because the integrity of the Sequence
Number has not been verified at this point.
Duplicates are rejected through the use of a sliding receive window.
The "right" edge of the window represents the highest, validated
Sequence Number value received on this session. Packets that contain
sequence numbers lower than the "left" edge of the window are
rejected. Packets falling within the window are checked against a
list of received packets within the window (how this list is managed
is a local, implementation based decision). This window limits how
far out of order a packet can be, relative to the packet with the
highest sequence number that has been authenticated so far.
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If the received packet falls within the window and is not a
duplicate, or if the packet is to the right of the window, then the
receiver proceeds to integrity verification. If the integrity check
fails, the receiver MUST discard the received packet as invalid,
otherwise the receive window is updated and packet processing
continues.
3.4. In Practice
Each packet sent MUST contain exactly one Digital Signature EXT_AUTH
header extension. A receiver MUST drop all the packets that do not
contain a Digital Signature EXT_AUTH header extension.
All receivers MUST recognize EXT_AUTH but MAY not be able to parse
its content, for instance because they do not support digital
signatures. In that case the Digital Signature EXT_AUTH header
extension is ignored.
If the anti-replay mechanism is used, each packet sent MUST contain a
valid sequence number. All the packets that fail to contain a valid
sequence number MUST be immediately dropped.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| HET (=1) | HEL (=33) | ASID | 0 |0| 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ---
| | ^ 1
+ + | 2
| | | 8
. . |
. Signature (128 bytes) . | b
. . | y
| | | t
+ + | e
| | v s
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ---
Figure 2: Example: Format of the Digital Signature EXT_AUTH header
extension using 1024 bit signatures, without any anti-replay
protection.
For instance Figure 2 shows the digital signature EXT_AUTH header
extension when using 128 byte (1024 bit) key digital signatures
(which also means that the signature field is 128 byte long). The
Digital Signature EXT_AUTH header extension is then 132 byte long.
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4. Elliptic Curve Digital Signature Scheme
This document focuses on the Elliptic Curve Digital Signature
Algorithm (ECDSA). However [RFC6090] describes alternative Elliptic
Curve techniques, like KT-I Signatures. The use of such alternatives
is not considered in this document, but may be added in the future.
4.1. Authentication Header Extension Format
The integration of ECC Digital Signatures is similar to that of RSA
Digital Signatures. Several fields are added in addition to the HET
(Header Extension Type) and HEL (Header Extension Length) fields, as
illustrated in Figure 1.
The fields of the Digital Signature EXT_AUTH header extension are:
"ASID" (Authentication Scheme IDentifier) field (4 bits):
The "ASID" identifies the source authentication scheme or protocol
in use. The association between the "ASID" value and the actual
authentication scheme is defined out-of-band, at session startup.
"Reserved" field (3 bits):
This is a reserved field that MUST be set to zero and ignored by
receivers.
"A" (Anti-replay) field (1 bit):
The "AR" field, when set to 0, indicates that the anti-replay
service is not used. When set to 1, it indicates that the anti-
replay service is used.
"SN" (Sequence Number) field (8 or 40 bits):
The "SN" field contains an optional sequence number. When AR=0,
this is an 8 bit field that MUST be set to zero. No anti-replay
mechanism is used in that case. When AR=1, this is a 32+8=40 bit
field and all of the 40 bits MUST be considered by the anti-replay
mechanism.
"Signature" field (variable size, multiple of 32 bits):
The "Signature" field contains a digital signature of the message.
If need be, this field is padded (with 0) up to a multiple of 32
bits.
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4.2. Parameters
Several parameters MUST be initialized by an out-of-band mechanism.
The sender or group controller:
o MUST communicate his public key, for each receiver to be able to
verify the signature of the packets received. As a side effect,
the receivers also know the key length and the signature length,
the two parameters being equal;
o MAY communicate a certificate (which also means that a PKI has
been setup), for each receiver to be able to check the sender's
public key;
o MUST communicate the Message Digest Algorithm;
o MUST communicate the Elliptic Curve;
o MUST associate a value to the "ASID" field (Authentication Scheme
IDentifier) of the EXT_AUTH header extension (Section 3.1);
o MUST communicate whether the anti-replay service is used or not
for this session;
These parameters MUST be communicated to all receivers before they
can authenticate the incoming packets. For instance it can be
communicated in the session description, or initialized in a static
way on the receivers, or communicated by means of an appropriate
protocol. The details of this out-of-band mechanism are out of the
scope of this document.
4.3. Processing
4.3.1. Signature Processing
The computation of the ECC digital signature, using the private key,
MUST include the ALC or NORM header (with the various header
extensions) and the payload when applicable. The UDP/IP/MAC headers
MUST NOT be included. During this computation, the "Signature" field
MUST be set to 0.
Several "Elliptic Curves" groups can be used, as well as several
"Hash Algorithms". In practice both choices are related and there is
a minimum hash algorithm size for any key length. Using a larger
hash algorithm and then truncated the output is also feasible,
however it consumes more processing power than is necessary. In
order to promote interoperability, [RFC4754] [RFC5480] list several
possible choices (see table below).
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+---------------------------+--------+------------------+-----------+
| Digital Signature | Key | Message Digest | Elliptic |
| Algorithm name [RFC4754] | Size | Algorithm | Curve |
+---------------------------+--------+------------------+-----------+
| ECDSA-256 (default) | 256 | SHA-256 | secp256r1 |
| | | | |
| ECDSA-384 | 384 | SHA-384 | secp384r1 |
| | | | |
| ECDSA-521 | 512 | SHA-512 | secp521r1 |
+---------------------------+--------+------------------+-----------+
The ECDSA-256, ECDSA-384 and ECDSA-521 are designed to offer security
comparable with AES-128, AES-192 and AES-256 respectively [RFC4754].
Among them, the use of ECDSA-256/secp256r1 is RECOMMENDED.
4.3.2. Anti-Replay Processing
The anti-replay processing follows the principles described in
Section 3.3.2.
4.4. In Practice
Each packet sent MUST contain exactly one ECC Digital Signature
EXT_AUTH header extension. A receiver MUST drop all the packets that
do not contain an ECC Digital Signature EXT_AUTH header extension.
All receivers MUST recognize EXT_AUTH but MAY not be able to parse
its content, for instance because they do not support ECC digital
signatures. In that case the Digital Signature EXT_AUTH header
extension is ignored.
If the anti-replay mechanism is used, each packet sent MUST contain a
valid sequence number. All the packets that fail to contain a valid
sequence number MUST be immediately dropped.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| HET (=1) | HEL (=9) | ASID | 0 |0| 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ---
| | ^ 3
+ + | 2
. . |
. Signature (32 bytes) . | b
. . | y
| | | t
+ + | e
| | v s
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ---
Figure 3: Example: Format of the ECC Digital Signature EXT_AUTH
header extension using ECDSA-256 signatures, without any anti-replay
protection.
For instance Figure 3 shows the digital signature EXT_AUTH header
extension when using ECDSA-256 (256 bit) ECC digital signatures. The
ECC Digital Signature EXT_AUTH header extension is then 36 byte long.
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5. Group-Keyed Message Authentication Code (MAC) Scheme
5.1. Authentication Header Extension Format
The integration of group-keyed MAC is similar in ALC and NORM and
relies on the header extension mechanism defined in both protocols.
More precisely this document details the HET=1 (EXT_AUTH) header
extension defined in [RFC5651].
Several fields are added in addition to the HET (Header Extension
Type) and HEL (Header Extension Length) fields (Figure 4).
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| HET (=1) | HEL | ASID | rsvd|A| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
~ anti-replay Sequence Number (SN) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ ~
| Group-keyed MAC |
+ +-+-+-+-+-+-+-+-+
| | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Format of the group-keyed MAC EXT_AUTH header extension.
The fields of the group-keyed MAC EXT_AUTH header extension are:
"ASID" (Authentication Scheme IDentifier) field (4 bits):
The "ASID" identifies the source authentication scheme or protocol
in use. The association between the "ASID" value and the actual
authentication scheme is defined out-of-band, at session startup.
"Reserved" field (3 bits):
This is a reserved field that MUST be set to zero and ignored by
receivers.
"A" (Anti-replay) field (1 bit):
The "AR" field, when set to 0, indicates that the anti-replay
service is not used. When set to 1, it indicates that the anti-
replay service is used.
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"SN" (Sequence Number) field (8 or 40 bits):
The "SN" field contains an optional sequence number. When AR=0,
this is an 8 bit field that MUST be set to zero. No anti-replay
mechanism is used in that case. When AR=1, this is a 32+8=40 bit
field and all of the 40 bits MUST be considered by the anti-replay
mechanism.
"Group-keyed MAC" field (variable size, multiple of 32 bits):
The "Group-keyed MAC" field contains a truncated Group-keyed MAC
of the message. If need be, this field is padded (with 0) up to a
multiple of 32 bits.
5.2. Parameters
Several parameters MUST be initialized by an out-of-band mechanism.
The sender or group controller:
o MUST communicate the Cryptographic MAC Function, for instance,
HMAC-SHA-1, HMAC-SHA-224, HMAC-SHA-256, HMAC-SHA-384, or HMAC-SHA-
512. As a side effect, with these functions, the receivers also
know the key length and the non truncated MAC output length.
Because of security threats on SHA-1, the use of HMAC-SHA-256 is
RECOMMENDED [RFC6194];
o MUST communicate the length of the truncated output of the MAC,
n_m, which depends on the Cryptographic MAC Function chosen. Only
the n_m left-most bits (most significant bits) of the MAC output
are kept. Of course, n_m MUST be lower or equal to the key
length;
o MUST communicate the group key to the receivers, confidentially,
before starting the session. This key might have to be
periodically refreshed for improved robustness;
o MUST associate a value to the "ASID" field (Authentication Scheme
IDentifier) of the EXT_AUTH header extension (Section 5.1);
o MUST communicate whether the anti-replay service is used or not
for this session;
These parameters MUST be communicated to all receivers before they
can authenticate the incoming packets. For instance it can be
communicated in the session description, or initialized in a static
way on the receivers, or communicated by means of an appropriate
protocol (this will be often the case when periodic re-keying is
required). The details of this out-of-band mechanism are out of the
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scope of this document.
5.3. Processing
5.3.1. Signature Processing
The computation of the group-keyed MAC, using the group key, includes
the ALC or NORM header (with the various header extensions) and the
payload when applicable. The UDP/IP/MAC headers are not included.
During this computation, the Weak group-keyed MAC field MUST be set
to 0. Then the sender truncates the MAC output to keep the n_m most
significant bits and stores the result in the group-keyed MAC
Authentication header.
Upon receiving this packet, the receiver computes the group-keyed
MAC, using the group key, and compares it to the value carried in the
packet. During this computation, the Group MAC field MUST also be
set to 0. If the check fails, the packet MUST be immediately
dropped.
[RFC2104] explains that it is current practice to truncate the MAC
output, on condition that the truncated output length, n_m be not
less than half the length of the hash and not less than 80 bits.
However, this choice is out of the scope of this document.
5.3.2. Anti-Replay Processing
The anti-replay processing follows the principles described in
Section 3.3.2.
5.4. In Practice
Each packet sent MUST contain exactly one group-keyed MAC EXT_AUTH
header extension. A receiver MUST drop packets that do not contain a
group-keyed MAC EXT_AUTH header extension.
All receivers MUST recognize EXT_AUTH but MAY not be able to parse
its content, for instance because they do not support group-keyed
MAC. In that case the group-keyed MAC EXT_AUTH extension is ignored.
If the anti-replay mechanism is used, each packet sent MUST contain a
valid sequence number. All the packets that fail to contain a valid
sequence number MUST be immediately dropped.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| HET (=1) | HEL (=4) | ASID | 0 |0| 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| group-keyed MAC (16 bytes) |
+ +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: Example: Format of the group-keyed MAC EXT_AUTH header
extension using HMAC-SHA-256, without any anti-replay protection.
For instance Figure 5 shows the group-keyed MAC EXT_AUTH header
extension when using HMAC-SHA-256. The group-keyed MAC EXT_AUTH
header extension is then 16 byte long.
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6. Combined Use of the RSA/ECC Digital Signatures and group-keyed MAC
Schemes
6.1. Authentication Header Extension Format
The integration of combined RSA/ECC Digital Signature and group-keyed
MAC is similar in ALC and NORM and relies on the header extension
mechanism defined in both protocols. More precisely this document
details the HET=1 (EXT_AUTH) header extension defined in [RFC5651].
Several fields are added in addition to the HET (Header Extension
Type) and HEL (Header Extension Length) fields (Figure 6).
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| HET (=1) | HEL | ASID | rsvd|A| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| anti-replay Sequence Number (SN) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ ~
| Signature |
+ +-+-+-+-+-+-+-+-+
| | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| group-keyed MAC |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: Format of the group-keyed MAC EXT_AUTH header extension.
The fields of the group-keyed MAC EXT_AUTH header extension are:
"ASID" (Authentication Scheme IDentifier) field (4 bits):
The "ASID" identifies the source authentication scheme or protocol
in use. The association between the "ASID" value and the actual
authentication scheme is defined out-of-band, at session startup.
"Reserved" field (3 bits):
This is a reserved field that MUST be set to zero and ignored by
receivers.
"A" (Anti-replay) field (1 bit):
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The "AR" field MUST be set to 1 and it indicates that the anti-
replay service is used (see Section 6.3).
"SN" (Sequence Number) field (8 or 40 bits):
The "SN" field contains a sequence number. Since AR=1, this is a
32+8=40 bit field and all of the 40 bits MUST be considered by the
anti-replay mechanism.
"Signature" field (variable size, multiple of 32 bits):
The "Signature" field contains a digital signature of the message.
If need be, this field is padded (with 0) up to a multiple of 32
bits.
"group-keyed MAC" field (variable size, multiple of 32 bits, by
default 32 bits):
The "group-keyed MAC" field contains a truncated group-keyed MAC
of the message.
6.2. Parameters
Several parameters MUST be initialized by an out-of-band mechanism,
as defined in Section 3.2, Section 4.2 and Section 5.2.
6.3. Processing
In some situations, it can be interesting to use both authentication
schemes. The goal of the group-keyed MAC is to mitigate DoS attacks
coming from attackers that are not group members [RFC4082] by adding
a light authentication scheme as a front-end.
6.3.1. Signature Processing
Before sending a message, the sender sets the Signature field and
group-keyed MAC field to zero. Then the sender computes the
Signature as detailed in Section 3.3 or in Section 4.3 and stores the
value in the Signature field. Then the sender computes the group-
keyed MAC as detailed in Section 5.3 and stores the value in the
group-keyed MAC field. The (RSA or ECC) digital signature value is
therefore protected by the group-keyed MAC, which avoids DoS attacks
where the attacker corrupts the digital signature itself.
Upon receiving the packet, the receiver first checks the group-keyed
MAC, as detailed in Section 5.3. If the check fails, the packet MUST
be immediately dropped. Otherwise the receiver checks the Digital
Signature, as detailed in Section 3.3. If the check fails, the
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packet MUST be immediately dropped.
This scheme features a few limits:
o the group-keyed MAC is of no help if a group member (who knows the
group key) impersonates the sender and sends forged messages to
other receivers. DoS attacks are still feasible;
o it requires an additional MAC computing for each packet, both at
the sender and receiver sides;
o it increases the size of the authentication headers. In order to
limit this problem, the length of the truncated output of the MAC,
n_m, SHOULD be kept small (see [RFC3711] section 9.5). In the
current specification, n_m MUST be a multiple of 32 bits, and
default value is 32 bits. As a side effect, with n_m = 32 bits,
the authentication service is significantly weakened since the
probability that any packet be successfully forged is one in 2^32.
Since the group-keyed MAC check is only a pre-check that is
followed by the standard signature authentication check, this is
not considered to be an issue.
For a given use-case, the benefits brought by the group-keyed MAC
must be balanced against these limitations.
6.3.2. Anti-Replay Processing
The anti-replay processing follows the principles described in
Section 3.3.2. Here an anti-replay service MUST be used. Indeed,
failing to enable anti-replay protection would facilitate DoS
attacks, since all replayed (but otherwise valid) packets would pass
the light authentication scheme and oblige a receiver to perform a
complex signature verification.
6.4. In Practice
Each packet sent MUST contain exactly one combined Digital Signature/
group-keyed MAC EXT_AUTH header extension. A receiver MUST drop
packets that do not contain a combined Digital Signature/group-keyed
MAC EXT_AUTH header extension.
All receivers MUST recognize EXT_AUTH but MAY not be able to parse
its content, for instance because they do not support combined
Digital Signature/group-keyed MAC. In that case the combined Digital
Signature/group-keyed MAC EXT_AUTH extension is ignored.
Since the anti-replay mechanism MUST be used, each packet sent MUST
contain a valid sequence number. All the packets that fail to
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contain a valid sequence number MUST be immediately dropped.
It is RECOMMENDED that the n_m parameter of the group authentication
scheme be small, and by default equal to 32 bits (Section 6.3).
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| HET (=1) | HEL (=35) | ASID | 0 |1| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| anti-replay Sequence Number (SN) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ---
| | ^ 1
+ + | 2
| | | 8
. . |
. Signature (128 bytes) . | b
. . | y
| | | t
+ + | e
| | v s
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ---
| group-keyed MAC (32 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ---
Figure 7: Example: Format of the combined RSA Digital Signature/
group-keyed MAC EXT_AUTH header extension using 1024 bit signatures,
with anti-replay protection.
For instance Figure 7 shows the combined Digital Signature/
group-keyed MAC EXT_AUTH header extension when using 128 byte (1024
bit) key RSA digital signatures (which also means that the signature
field is 128 byte long). The EXT_AUTH header extension is then 140
byte long.
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7. IANA Considerations
This document does not require any IANA registration.
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8. Security Considerations
8.1. Dealing With DoS Attacks
Let us consider packets secured through the use of a digital
signature scheme first. Because faked packets are easy to create but
checking them requires to compute a costly digital signature, this
scheme introduces new opportunities for an attacker to mount DoS
attacks. More precisely an attacker can easily saturate the
processing capabilities of the receiver.
In order to mitigate these attacks, it is RECOMMENDED to use the
combined Digital Signature/group-keyed MAC scheme (Section 6.3).
However, no mitigation is possible if a group member acts as an
attacker. Additionally, even if checking a group-keyed MAC is
significantly faster than checking a digital signature, there are
practical limits on how many group-keyed MAC can be checked per time
unit. Therefore it is RECOMMENDED to limit the number of
authentication checks per time unit when the number of incoming
packets that fail the authentication check exceeds a given threshold
(i.e., in case of a DoS attack).
The RECOMMENDATION to limit the number of checks per time unit under
(presumed) attack situations can be extended to the other
authentication schemes.
8.2. Dealing With Replay Attacks
Replay attacks consist for an attacker to store a valid message and
to replay it later on. It is RECOMMENDED to use the anti-replay
service defined in this document with the signature and group-keyed
MAC solutions, and this anti-replay service MUST be used in case of a
combined use of signature and group-keyed MAC (see Section 6.3.2).
The following section details some of the potential consequences of
not using the anti-replay protection.
8.2.1. Impacts of Replay Attacks on the Simple Authentication Schemes
Since all the above authentication schemes are stateless, replay
attacks have no impact on these schemes.
8.2.2. Impacts of Replay Attacks on NORM
We review here the potential impacts of a replay attack on the NORM
component. Note that we do not consider here the protocols that
could be used along with NORM, for instance the congestion control
protocols.
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First, let us consider replay attacks within a given NORM session.
NORM being a stateful protocol, replaying a packet may have
consequences.
NORM defines a "sequence" field that may be used to protect against
replay attacks [RFC5740] within a given NORM session. This
"sequence" field is a 16-bit value that is set by the message
originator (sender or receiver) as a monotonically increasing number
incremented with each NORM message transmitted. Using this field as
an anti-replay protection would be possible if there is no wrapping
to zero, i.e., would only be possible if at most 65535 packets are
sent. This may be true for some use-cases but not for the general
case. Using this field as an anti-replay protection would also be
possible if the keying material is updated before wrapping to zero
happens. This may be true for some use-cases but not for the general
case.
Now let us consider replay attacks across several NORM sessions. A
host participation in a NORM session is uniquely identified by the
{"source_id"; "instance_id"} tuple. Therefore, when a given host
participates in several NORM sessions, it is RECOMMENDED that the
"instance_id" be changed for each NORM instance. It is also
RECOMMENDED, when the group-keyed MAC authentication/integrity check
scheme is used, that the shared group key be changed across sessions.
Therefore, NORM can be made robust in front of replay attacks across
different sessions.
8.2.3. Impacts of Replay Attacks on ALC
We review here the potential impacts of a replay attack on the ALC
component. Note that we do not consider here the protocols that
could be used along with ALC, for instance the layered or wave based
congestion control protocols.
First, let us consider replay attacks within a given ALC session:
o replayed encoding symbol: a replayed encoding symbol (coming from
a replayed data packet) is detected thanks to the object/block/
symbol identifiers and is silently discarded.
o replayed control information: more precisely:
* At the end of the session, a "close session" (A flag) packet is
sent. Replaying a packet containing this flag has no impact
since the receivers already left.
* Similarly, replaying a packet containing a "close object" (B
flag) has no impact since this object is probably already
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marked as closed by the receiver.
* Timing information sent as part of an LCT EXT_TIME header
extension [RFC5651] may be more sensitive to replay attacks.
For instance replaying a packet containing an ERT (Expected
Residual Time) may mislead a receiver to believe an object
transmission will continue for some time whereas the
transmission of symbols for this object is about to stop.
Replaying a packet containing a SCT (Sender Current Time) is
easily identified if the receiver verifies that time progresses
upon receiving such EXT_TIME header extensions. Replaying a
packet containing a SLC (Session Last Changed) is easily
identified if the receiver verifies the chronology upon
receiving such EXT_TIME header extensions.
This analysis shows that ALC might be, to a limited extent, sensitive
to replay attacks within the same session if timing information is
used. Otherwise ALC is robust in front of replay attacks within the
same session.
Now let us consider replay attacks across several ALC sessions. An
ALC session is uniquely identified by the {sender's IP address;
Transport Session Identifier (TSI)}. Therefore, when a given sender
creates several sessions, the TSI MUST be changed for each ALC
session, so that each TSI is unique among all active sessions of this
sender and for a large period of time preceding and following when
the session is active [RFC5651]. Therefore, ALC can be made robust
in front of replay attacks across different sessions. Of course,
when the group-keyed MAC authentication/integrity check scheme is
used, the shared group key SHOULD be changed across sessions if the
set of receivers changes.
8.3. Dealing With Attacks on the Parameters Sent Out-of-Band
This specification requires several parameters to be communicated to
the receiver(s) via an out-of-band mechanism that is out of the scope
of this document. This is in particular the case for the mapping
between an ASID value and the associated authentication scheme
(Section 1). Since this mapping is critical, this information SHOULD
be carried in a secure way from the sender to the receiver(s).
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9. Acknowledgments
The author is grateful to the authors of [RFC4303], [RFC4359],
[RFC4754] and [RFC5480] that inspired several sections of the present
document. The author is also grateful to all the IESG members, and
in particular to David Harrington, Stephen Farrell and Sean Turner
for their very detailed reviews.
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10. References
10.1. Normative References
[RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
Hashing for Message Authentication", RFC 2104,
February 1997.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, BCP 14, March 1997.
[RFC5651] Luby, M., Watson, M., and L. Vicisano, "Layered Coding
Transport (LCT) Building Block", RFC 5651, October 2009.
[RFC5740] Adamson, B., Bormann, C., Handley, M., and J. Macker,
"NACK-Oriented Reliable Multicast (NORM) Transport
Protocol", RFC 5740, November 2009.
[RFC5775] Luby, M., Watson, M., and L. Vicisano, "Asynchronous
Layered Coding (ALC) Protocol Instantiation", RFC 5775,
April 2010.
10.2. Informative References
[RFC3447] Jonsson, J. and B. Kaliski, "Public-Key Cryptography
Standards (PKCS) #1: RSA Cryptography Specifications
Version 2.1", RFC 3447, February 2003.
[RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K.
Norrman, "The Secure Real-time Transport Protocol (SRTP)",
RFC 3711, March 2004.
[RFC4082] Perrig, A., Song, D., Canetti, R., Tygar, J., and B.
Briscoe, "Timed Efficient Stream Loss-Tolerant
Authentication (TESLA): Multicast Source Authentication
Transform Introduction", RFC 4082, June 2005.
[RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)",
RFC 4303, December 2005.
[RFC4359] Weis, B., "The Use of RSA/SHA-1 Signatures within
Encapsulating Security Payload (ESP) and Authentication
Header (AH)", RFC 4359, January 2006.
[RFC4754] Fu, D. and J. Solinas, "IKE and IKEv2 Authentication Using
the Elliptic Curve Digital Signature Algorithm (ECDSA)",
RFC 4754, January 2007.
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[RFC5480] Turner, S., Brown, D., Yiu, K., Housley, R., and T. Polk,
"Elliptic Curve Cryptography Subject Public Key
Information", RFC 5480, March 2009.
[RFC5751] Ramsdell, B. and S. Turner, "Secure/Multipurpose Internet
Mail Extensions (S/MIME) Version 3.2 Message
Specification", RFC 5751, January 2010.
[RFC5776] Roca, V., Francillon, A., and S. Faurite, "Use of Timed
Efficient Stream Loss-Tolerant Authentication (TESLA) in
the Asynchronous Layered Coding (ALC) and NACK-Oriented
Reliable Multicast (NORM) Protocols", RFC 5776,
April 2010.
[RFC6090] McGrew, D., Igoe, K., and M. Salter, "Fundamental Elliptic
Curve Cryptography Algorithms", RFC 6090, February 2011.
[RFC6194] Polk, T., Chen, L., Turner, S., and P. Hoffman, "Security
Considerations for the SHA-0 and SHA-1 Message-Digest
Algorithms", RFC 6194, March 2011.
[RMT-FLUTE]
Paila, T., Walsh, R., Luby, M., Roca, V., and R. Lehtonen,
"FLUTE - File Delivery over Unidirectional Transport",
Work in Progress, February 2011.
Roca Expires June 11, 2012 [Page 33]
Internet-Draft Simple authentication for ALC and NORM December 2011
Author's Address
Vincent Roca
INRIA
655, av. de l'Europe
Inovallee; Montbonnot
ST ISMIER cedex 38334
France
Email: vincent.roca@inria.fr
URI: http://planete.inrialpes.fr/people/roca/
Roca Expires June 11, 2012 [Page 34]
