Network Working Group B. Sarikaya
Internet-Draft F. Xia
Intended status: Standards Track Huawei USA
Expires: April 7, 2011 October 4, 2010
Lightweight Secure Neighbor Discovery for Low-power and Lossy Networks
draft-sarikaya-lwip-cgand-00
Abstract
This document defines lightweight secure neighbor discovery for low-
power and lossy networks. The nodes generate a Cryptographically
Generated Address using an Elliptic Curve Cryptography public key,
register the Cryptographically Generated Address with a default
router and periodically refresh the registration. Modifications to
6lowpan Neighbor Discovery protocol are described for secure neighbor
discovery for low-power and lossy networks. Cryptographically
generated address and digital signature are calculated using elliptic
curve cryptography public key of the node.
Status of this Memo
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This Internet-Draft will expire on April 7, 2011.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 4
4. New Options . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.1. CGA Parameters and Digital Signature Option . . . . . . . 4
4.2. Digital Signature Option . . . . . . . . . . . . . . . . . 6
4.3. Calculation of Digital Signature and CGA Using ECC . . . . 7
5. Protocol Interactions . . . . . . . . . . . . . . . . . . . . 7
5.1. Packet Sizes . . . . . . . . . . . . . . . . . . . . . . . 9
6. Security Considerations . . . . . . . . . . . . . . . . . . . 10
7. IANA considerations . . . . . . . . . . . . . . . . . . . . . 10
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
9.1. Normative References . . . . . . . . . . . . . . . . . . . 10
9.2. Informative references . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11
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1. Introduction
Neighbor discovery for IPv6 [RFC4861] and stateless address
autoconfiguration [RFC4862] together referred to as neighbor
discovery protocols (NDP) are defined for regular hosts operating in
wired/wireless links. These protocols are not suitable and require
optimizations for resource constrained, low power hosts operating in
lossy wireless links. Neighbor discovery optimizations for 6lowpan
networks include simple optimizations such as host address
registration feature using the address registration option which is
sent in unicast Neighbor Solicitation (NS) and Neighbor Advertisement
(NA) messages [I-D.ietf-6lowpan-nd].
Neighbor discovery protocols (NDP) are not secure especially when
physical security on the link is not assured and vulnerable to
attacks. Secure neighbor discovery protocol (SEND) is defined to
secure NDP [RFC3971]. Cryptographically generated addresses (CGA)
are used in SEND [RFC3972]. SEND mandates the use of RSA signature
algorithm which is computationally heavy and not suitable to use for
low-power and resource constrained nodes
[I-D.cheneau-csi-send-sig-agility]. The use of RSA public key and
signature leads to long message sizes not suitable to use in low-bit
rate, short range, asymmetric and non-transitive links such as IEEE
802.15.4.
In this document we extend 6lowpan neighbor discovery protocol with
cryptographically generated addresses. The nodes generate CGAs and
register them with the default router. CGA generation is based on
elliptic curve cryptography (ECC)and signature is calculated using
elliptic curve digital signature algorithm (ECDSA) known to be
lightweight and lead to much smaller packet sizes. The resulting
protocol is called Lightweight Secure Neighbor Discovery Protocol
(LSEND).
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].
The terminology in this document is based on the definitions in
[RFC3971], [RFC3972] in addition to the ones specified in
[I-D.ietf-6lowpan-nd].
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3. Problem Statement
In this section we state requirements on secure neighbor discovery
protocol for low-power and lossy networks.
The protocol MUST be based on Neighbor Discovery Optimization for
Low-power and Lossy Networks protocol defined in
[I-D.ietf-6lowpan-nd] due to the host-initiated interactions to allow
for sleeping hosts, elimination of multicast-based address resolution
for hosts, etc.
New options to be added to neighbor solicitation messages MUST lead
to minimal packet sizes. Such packet sizes facilitate low-power
transmission by resource constrained nodes on lossy links.
CGA generation, signature and key hash calculation MUST avoid the use
of SHA-1 which is known to have security flaws. In this document, we
use SHA-2 instead of SHA-1 and thus avoid SHA-1's flaws.
Public key and signature sizes MUST be minimized and signature
calculation MUST be lightweight. In this document we adopt ECC and
ECDSA with P-256 curve in order to meet this requirement.
4. New Options
4.1. CGA Parameters and Digital Signature Option
This option contains both CGA parameters and the digital signature.
A summary of the CGA Parameters and Digital Signature Option format
is shown below.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Pad Length | Sig. Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. CGA Parameters .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. Digital Signature .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. Padding .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
TBA1 for CGA Parameters and Digital Signature
Length
The length of the option (including the Type, Length, Pad Length,
Signature Length, CGA Parameters, Digital Signature and Padding
fields) in units of 8 octets.
Pad Length
The length of the Padding field.
Sig Length
The length of the Digital Signature field.
CGA Parameters
The CGA Parameters field is variable-length containing the CGA
Parameters data structure described in Section 4 of [RFC3972].
Digital Signature
The Digital Signature field is a variable length field containing
a Elliptic Curve Digital Signature Algorithm (ECDSA) signature
(with SHA-256 and P-256 curve of [FIPS-186-3]). Digital signature
is constructed as explained in Section 4.3.
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Padding
The Padding field contains a variable-length field making the CGA
Parameters and Digital Signature Option length a multiple of 8.
4.2. Digital Signature Option
This option contains the digital signature.
A summary of the Digital Signature Option format is shown below.
Note that this option has the same format as RSA Signature Option
defined in [RFC3971]. The differences are that Digital Signature
field carries Ellictic Curve Cryptography signature not RSA signature
and in calculating Key Hash field SHA-2 is used not SHA-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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Key Hash |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. Digital Signature .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. Padding .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
TBA2 for Digital Signature
Length
The length of the option (including the Type, Length, Reserved,
Key Hash, Digital Signature and Padding fields) in units of 8
octets.
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Key Hash
The Key Hash field is a 128-bit field containing the most
significant (leftmost) 128 bits of a SHA-2 hash of the public key
used for constructing the signature. This is the same as in
[RFC3971] except for SHA-1 which has been proved to be flawed in
the light of recent attacks [NIST-ST].
Digital Signature
Same as in Section 4.1.
Padding
The Padding field contains a variable-length field containing as
many bytes long as remain after the end of the signature.
4.3. Calculation of Digital Signature and CGA Using ECC
Due to the use of Elliptic Curve Cryptography, the following
modifications are needed to [RFC3971] and [RFC3972].
Digital signature is constructed by using the sender's private key
over the same sequence of octets specified in Section 5.2 of
[RFC3971] up to all neighbor discovery protocol options preceding the
Digital Signature option containing Elliptic Curve Cryptography
digital signature. The signature value is computed using the ECDSA
signature algorithm as defined in [SEC1] and hash function SHA-256.
Public Key is the most important parameter in CGA Parameters defined
in Section 4.1. Public Key MUST be DER-encoded ASN.1 structure of
the type SubjectPublicKeyInfo formatted as ECC Public Key. The
AlgorithmIdentifier, contained in ASN.1 structure of type
SubjectPublicKeyInfo, MUST be the (unrestricted) id- ecPublicKey
algorithm identifier, which is OID 1.2.840.10045.2.1, and the
subjectPublicKey MUST be formatted as an ECC Public Key, specified in
Section 2.2 of [RFC5480].
Note that the ECC key lengths are determined by the namedCurves
parameter stored in ECParameters field of the AlgorithmIdentifier.
The named curve to use is secp256r1 corresponding to P-256 which is
OID 1.2.840.10045.3.1.7.
5. Protocol Interactions
Lightweight Secure Neighbor Discovery for Low-power and Lossy
Networks (LSEND for LLN) modifies Neighbor Discovery Optimization for
Low-power and Lossy Networks [I-D.ietf-6lowpan-nd] as explained in
this section. Protocol interactions are shown in Figure 1.
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6LoWPAN Border Routers (6LBR) send router advertisements (RA).
6LoWPAN Nodes (6LN) or nodes in short receive these RAs and generate
their own cryptographically generated addresses using elliptic curve
cryptography as explained in Section 4.3. The node sends a neighbor
solicitation (NS) message with address registration option (ARO) to
6LBR. Such a NS is called an address registration NS.
A LSEND for LLN node MUST send an address registration NS message
after adding CGA Parameters and Digital Signature Option defined in
Section 4.1. Source address MUST be set to its crypotographically
generated address. A LSEND for LLN node MUST set the Owner Interface
Identifier field (EUI-64) in ARO to the rightmost 64 bits of its
crypotographically generated address. Subnet Prefix field of CGA
Parameters MUST be set to the leftmost 64 bits of its
crypotographically generated address. Public Key field of CGA
Parameters MUST be set to the node's ECC Public Key.
6LBR receives the address registration NS. 6LBR verifies the source
address as described in Section 5.1.2. of [RFC3971] using the claimed
source address and CGA Parameters field in the message. After
successfully verifying the address 6LBR next does a cryptographic
check of the signature included in Digital Signature field in the
message. If all checks succeed then 6LBR performs a duplicate
address detection procedure first on the address. If that also
succeeds 6LBR registers CGA in the neighbor cache. 6LBR also caches
the node's public key.
6LBR sends an address registration neighbor advertisement (NA) as a
reply to confirm the node's registration. Status is set to 0 to
indicate success. This completes initial address registration. The
address registration needs to be refreshed after the neighbor cache
entry times out.
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6LN 6LBR
| |
|<-----------------------RA-------------------------------|
| |
|---------------NS with ARO and CGA Option--------------->|
| |
|<-----------------------NA with ARO----------------------|
| |
|---------------NS with ARO and Digital Signature Option->|
| |
|<-----------------------NA with ARO----------------------|
| |
|---------------NS with ARO and Digital Signature Option->|
| |
|<-----------------------NA with ARO----------------------|
Figure 1: Lightweight SEND for LLA Protocol
In order to refresh the neighbor cache entry, a LSEND for LLN node
MUST send an address registration NS message after adding Digital
Signature Option defined in Section 4.2. Key hash field is a hash of
the node's public key and MUST be set as described in Section 4.2.
Digital Signature field MUST be set as described in Section 4.2.
6LBR receives the address registration refresh NS. 6LBR uses the key
hash field in Digital Signature Option to find the node's public key
from the neighbor cache. 6LBR verifies the digital signature in the
NS. In case of successful verification, 6LBR sends back an address
registration neighbor advertisement (NA) to the node and sets the
status to 0 indicating successful refreshment of the CGA of the node.
Similar refresh NS and NA exchanges happen afterwards as shown in
Figure 1
5.1. Packet Sizes
Original address registration NS message contains 40 byte header and
ARO is 16 octets. DER-encoded ECC Public Key for P-256 curve is 88
octets long. Digital Signature field when using ECDSA for P-256
curve is 71 octets long without padding
[I-D.cheneau-csi-ecc-sig-agility].
CGA Parameters and Digital Signature Option's CGA Parameters include
16 octet modifier, 8 octet prefix obtained from the router
advertisement message sent from 6LBR, 1 octet collision count and 88
octet Public Key. Digital Signature is 71 octets. The option is 184
octets with Padding 0 octets. The total message size of an original
LSEND address registration NS message is 240 octets and such a
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message can be encapsulated into three 802.15.4 frames.
An address registration refresh NS message contains an ARO which is
16 octets and digital signature option containing 16 octet key hash
and 71 octet signature and 5 octet Padding. The message is 152
octets long with the header. Such a message could be encapsulated in
two 802.15.4 frames.
6. Security Considerations
Same considerations regarding the threats to the Local Link Not
Covered as in [RFC3971] apply.
The threats discussed in Section 9.2 of [RFC3971] are countered by
the protocol described in this document as well.
As to the attacks to the protocol itself, denial of service attacks
that involve producing a very high number of packets are deemed
unlikely because of the assumptions on the node capabilities in low-
power and lossy networks.
7. IANA considerations
This document defines two new options to be used in neighbor
discovery protocol messages and new type values for CGA Parameters
and Digital Signature Option (TBA1) and Digital Signature Option
(TBA2) need to be assigned by IANA.
8. Acknowledgements
TBD.
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3971] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure
Neighbor Discovery (SEND)", RFC 3971, March 2005.
[RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)",
RFC 3972, March 2005.
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[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
September 2007.
[RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
Address Autoconfiguration", RFC 4862, September 2007.
[RFC5480] Turner, S., Brown, D., Yiu, K., Housley, R., and T. Polk,
"Elliptic Curve Cryptography Subject Public Key
Information", RFC 5480, March 2009.
[I-D.ietf-6lowpan-nd]
Shelby, Z., Chakrabarti, S., and E. Nordmark, "Neighbor
Discovery Optimization for Low-power and Lossy Networks",
draft-ietf-6lowpan-nd-13 (work in progress),
September 2010.
9.2. Informative references
[SEC1] "Standards for Efficient Crtptography Group. SEC 1:
Elliptic Curve Cryptography", September 2000.
[FIPS-186-3]
"National Institute of Standards and Technology, "Digital
Signature Standard"", June 2009.
[NIST-ST] "National Institute of Standards and Technology, "NIST
Comments on Cryptanalytic Attackts on SHA-1"",
January 2009,
<http://csrc.nist.gov/groups/ST/hash/statement.html>.
[I-D.cheneau-csi-ecc-sig-agility]
Cheneau, T., Laurent, M., Shen, S., and M. Vanderveen,
"ECC public key and signature support in Cryptographically
Generated Addresses (CGA) and in the Secure Neighbor
Discovery (SEND)", draft-cheneau-csi-ecc-sig-agility-02
(work in progress), June 2010.
[I-D.cheneau-csi-send-sig-agility]
Cheneau, T., Laurent, M., Shen, S., and M. Vanderveen,
"Signature Algorithm Agility in the Secure Neighbor
Discovery (SEND) Protocol",
draft-cheneau-csi-send-sig-agility-02 (work in progress),
June 2010.
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Authors' Addresses
Behcet Sarikaya
Huawei USA
1700 Alma Dr. Suite 500
Plano, TX 75075
Phone: +1 972-509-5599
Email: sarikaya@ieee.org
Frank Xia
Huawei USA
1700 Alma Dr. Suite 500
Plano, TX 75075
Phone: +1 972-509-5599
Email: xiayangsong@huawei.com
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