6lo B. Sarikaya Internet-DraftHuawei USAUpdates: 6775 (if approved) P. Thubert Intended status: Standards Track Cisco Expires:NovemberMarch 25,20172018 M. Sethi EricssonMay 24,September 21, 2017 Address Protected Neighbor Discovery for Low-power and Lossy Networksdraft-ietf-6lo-ap-nd-02draft-ietf-6lo-ap-nd-03 Abstract This document defines an extension to 6LoWPAN NeighborDiscovery,Discovery RFC 6775. Nodes supporting this extension compute a cryptographic Owner Unique Interface ID and associate it with one or more of their Registered Addresses. Once an address is registered with a Cryptographic ID, only the owner of that ID can modify the anchor state information of the Registered Address, and Source Address Validation can be enforced. 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 athttp://datatracker.ietf.org/drafts/current/.https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire onNovemberMarch 25,2017.2018. Copyright Notice Copyright (c) 2017 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)(https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Updating RFC 6775 . . . . . . . . . . . . . . . . . . . . . . 4 4. New Fields and Options . . . . . . . . . . . . . . . . . . . 5 4.1. New Crypto-ID . . . . . . . . . . . . . . . . . . . . . . 5 4.2. Updated EARO . . . . . . . . . . . . . . . . . . . . . . 6 4.3. New Crypto-ID Parameters Option . . . . . . . . . . . . . 7 5. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 8 5.1. Protocol Scope . . . . . . . . . . . . . . . . . . . . . 8 5.2. Protocol Flows . . . . . . . . . . . . . . . . . . . . . 9 5.3. Multihop Operation . . . . . . . . . . . . . . . . . . . 11 6. Security Considerations . . . . . . . . . . . . . . . . . . . 12 7. IANA considerations . . . . . . . . . . . . . . . . . . . . . 13 7.1. Crypto Type Registry . . . . . . . . . . . . . . . . . . 13 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13 9. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 13 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 13 10.1. Normative References . . . . . . . . . . . . . . . . . .1314 10.2. Informative references . . . . . . . . . . . . . . . . . 14 Appendix A. Requirements Addressed in this Document . . . . . . 16 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17 1. IntroductionNeighbor discovery"Neighbor Discovery Optimizations forIPv6 [RFC4861] and stateless address autoconfiguration [RFC4862] and their extensions are collectively referred to as6LoWPAN networks" [RFC6775] (6LoWPAN ND) adapts the classical IPv6Neighbor Discovery ProtocolND protocol [RFC4861][RFC4862] (IPv6NDP). In order to enable IPv6 NDPND) for operations over a constrained low-power and lossy network(LLN), "Neighbor Discovery optimizations for(LLN). In particular, 6LoWPANnetworks" [RFC6775] (6LoWPAN ND), reduces the use of multicast in the original protocol andND introduces a unicast host address registrationtechnique. The registrationmechanismleveragesthat contributes to reduce the use of multicast messages that are present in the classical IPv6 ND protocol. 6LoWPAN ND defines a new Address Registration Option (ARO) that is carried in the unicast Neighbor Solicitation (NS) and Neighbor Advertisement (NA) messages between the 6LoWPAN Node (6LN) and the 6LoWPAN Router(6LR), as well as(6LR). Additionally, it also defines the Duplicate Address Request (DAR) and Duplicate Address Confirmation (DAC) messages between the 6LR and the 6LoWPAN Border Router(6LBR), which(6LBR). In LLN networks, the 6LBR is the central repository of all the registered addresses in its domain. The registration mechanism in 6LoWPAN ND [RFC6775]was created forprevents theoriginal purpose of Duplicate Address Detection (DAD), wherebyuse of an addresswould be granted as long as theif that address isnotalready present in the subnet (first come first serve). In order to validate address ownership, the registration mechanism enables the 6LR and 6LBR tocorrelate furthervalidate claims for a registered addressfrom the device to which it is grantedwithaan associated Owner Unique Interface IDentifier (OUID).With6LoWPANND,ND specifies that the OUID is derived from the MAC address of the device (EUI-64), which can be spoofed. Therefore, any node connected to the subnet and aware of aregistered-address-to- OUIDregistered-address-to-OUID mappingmaycould effectively fake the OUID, steal the address andattract theredirect traffic for that address towards a differentNode. In order to allow a more secured registration mechanism, the6LN. The "Update to 6LoWPAN ND" [I-D.ietf-6lo-rfc6775-update]opens the semantics of thedefines an Extended ARO (EARO) optionandthat allows to transport alternate forms ofOUIDs. WithOUIDs, and is a prerequisite for this specification. According to this specification, a 6LN generates a cryptographic ID(Crypto- ID)(Crypto-ID) and places it in the OUID field in the registration of one (or more) of its addresses with the 6LR(s) thatitthe 6LN uses as default router(s). Proof of ownership of the cryptographic ID (Crypto-ID) is passed with the first registration to a given 6LR, and enforced at the 6LR, in a new Crypto-ID Parameters Option (CIPO). The 6LR validates ownership of the cryptographic ID upon the creation of a registration state, or a change in the anchor information, such as Link-Layer Address and associated Layer-2 cryptographic material. The protected address registration protocol proposed in this document enables the enforcement of Source Address Validation (SAVI) [RFC7039], which ensures that only the correct owner uses a registered address in the source address field in IPv6 packets.With this specification,Consequently, a 6LN that sources a packet has to use a 6LR to which the source address of the packet is registered to forward the packet. The 6LR maintains state information for the registeredaddressed along withaddressed, including the MAC address, and a link-layer cryptographic key associated withthat node.the 6LN. In SAVI-enforcement mode, the 6LR allows only packets from a connected Host if the connected Host owns the registration of the source address of the packet. The 6lo adaptation layer framework ([RFC4944], [RFC6282]) expects that a device forms its IPv6 addresses based on Layer-2 address, so as to enable a better compression. This is incompatible with "Secure Neighbor Discovery (SEND)" [RFC3971] and "Cryptographically Generated Addresses (CGAs)" [RFC3972], which derive the Interface ID (IID) in the IPv6 addresses from cryptographic material. "Privacy Considerations for IPv6 Address Generation Mechanisms"[I-D.ietf-6man-ipv6-address-generation-privacy][RFC7721] places additional recommendations on the way addresses should be formed and renewed. Thisspecification allowsdocument specifies that a devicetomay form and register addresses at will, without a constraint on the way the address is formed or the number of addresses that are registered in parallel. It enables to protect multiple addresses with a single cryptographic material and to send the proof only once to a given 6LR for multiple addresses and refresher registrations. 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]. Readers are expected to be familiar with all the terms and concepts that are discussed in [RFC3971], [RFC3972], [RFC4861], [RFC4919], [RFC6775], and [I-D.ietf-6lo-backbone-router] which proposes an evolution of [RFC6775] for wider applicability. This document defines Crypto-ID as an identifier of variable size which in most cases is 64 bits long. It is generated using cryptographic means explained later in thisdocument.document Section 4.1. The document also conforms to the terms and models described in [RFC5889] and uses the vocabulary and the concepts defined in [RFC4291] for the IPv6 Architecture.This document uses [RFC7102] for Terminology inFinally, common terminology related to Low power And LossyNetworks.Networks (LLN) defined in [RFC7102] is also used. 3. Updating RFC 6775With this specification, a node SHOULD useThis specification defines a cryptographic identifier (Crypto-ID) that can be used asOUIDa replacement to the MAC address inits registration;the OUID field of the EARO option; the computation of the Crypto-ID iscalculated as describeddetailed in Section 4.1.The fact thatA node in possession of the necessary cryptographic material SHOULD use Crypto-ID by default as OUID in its registration. Whether a OUID is a Crypto-ID is indicatedinby a new'C'"C" flag in theNS(ARO)NS(EARO) message. This specificationalsointroduces a new option, the CIPO, that is used to prove ownership of the Crypto-ID. A node that registers for the first time to a 6LR SHOULD place a CIPO optiontoin itsregistration butregistration. However, it is not expected to place the option in thenextperiodic refresher registrations for that address, orfor the registration ofto register other addresses with the same OUID. When a 6LR receives aNS(ARO)NS(EARO) registration with a new Crypto-ID as a OUID,thenit SHOULD challenge by responding with aNA(ARO)NA(EARO) with a status of"Proof requested"."Validation Requested". Thiswholeprocess of validation MAY be skipped in networks where there is noor ultra low expectations ofmobility. The challengewillMUST also be triggered in the case of a registration for which the Source Link-Layer Address is not consistent with a state that already exists either at the 6LR or the 6LBR. In the latter case, the 6LBR returns a status of"Proof requested""Validation Requested" in the DAR/DAC exchange, which is echoed by the 6LR in the NA(ARO)(EARO) back to the registering node. This flow should not alter a preexisting state in the 6LR or the 6LBR. Upon receiving aNA(ARO)NA(EARO) with a status of"Proof requested","Validation Requested", the registering node SHOULD retry its registration with a CIPO option that proves its ownership of the Crypto-ID. If the 6LR cannot validate theproof,CIPO, it responds with a status of"Incorrect Proof". Upon"Validation Failed". After receiving aNA(ARO)NA(EARO) with a status of"Incorrect Proof","Validation Failed", the registering nodeSHOULDMUST NOT use this Crypto-ID for registering with that6LR anymore.6LR. 4. New Fields and Options 4.1. New Crypto-ID Elliptic Curve Cryptography (ECC) is usedin the calculation ofto calculate the Crypto-ID. Each 6LN using a Crypto-ID for registration MUST have a public/ private key pair. The digital signature is constructed by using the 6LN's private key over its EUI-64 (MAC) address. The signature value is computed using the ECDSA signature algorithm and the hash function used is SHA-256 [RFC6234]. Public Key is the most important parameter in CGA Parameters (sent by 6LN in an NS message). ECC Public Key could be in uncompressed form or in compressed form where the first octet of the OCTET STRING is 0x04 and 0x02 or 0x03, respectively. Point compression can further reduce the key size by about 32 octets.First,The Crypto-ID is computed as follows: 1. the modifier is set to a random or pseudo-random 128-bitvalue. Next, concatenate from left to rightvalue 2. the modifier, 9 zero octets and the ECC publickey.key are concatenated from left to right. 3. the SHA-256 algorithm is applied on theconcatenation. Theconcatenation 4. the 112 leftmost bits of the hash valueis taken. Concatenate from left to rightare retained 5. the modifier value, the subnet prefix and the encoded publickey.key are concatenated from left to right 6. NIST P-256 is executed on theconcatenation. Theconcatenation 7. the leftmost bits of the resultisare used as the Crypto-ID. With this specification, the last 64 bits are retained, but it could be expanded to more bits in the future by increasing the size of the OUID field.In respecting theTo support cryptographic algorithm agility [RFC7696],Curve 25519Curve25519 [RFC7748] can also be used instead of NIST P-256. This is indicated by 6LNby settingusing the Crypto Type field in the CIPOoption to aoption. The document currently only defines two possible values for the Crypto Type field. A value of1. If 6LBR does not support Curve 25519, it will set0 indicates that NIST P-256 is used for the signature operation and SHA-256 as the hash algorithm. A value of 1 indicates that Curve25519 is used for the signature operation and SHA-256 as the hash algorithm. New values for the Crypto Typefield to zero. This means thatmaybe defined in thedefault algorithm (NIST P-256) will be used.future for new curves. 4.2. Updated EARO This specification updates the EARO option as follows: 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 | Status | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved |C|T| TID | Registration Lifetime | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + Owner Unique ID (EUI-64 or equivalent) + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: Enhanced Address Registration Option Type: 33 Length: 8-bit unsigned integer. The length of the option (including the type and length fields) in units of 8 bytes. Status: 8-bit unsigned integer. Indicates the status of a registration in the NA response. MUST be set to 0 in NS messages. This specificationleveragesuses values introduced in theUpdateupdate to 6LoWPAN ND [I-D.ietf-6lo-rfc6775-update], such as5: Proof Requested,"Validation Requested" anddoes not require"Validation Failed". No additionalvalues to bevalue is defined. Reserved: This field is unused. It MUST be initialized to zero by the sender and MUST be ignored by the receiver. C: Thisspecification introduces a C bit, which"C" flag is set to indicate that the Owner Unique ID field contains a Crypto-ID. T and TID: Defined in [I-D.ietf-6lo-rfc6775-update]. Owner Unique ID: Whenusing this specification,the "C" flag is set, this field contains a Crypto-ID. 4.3. New Crypto-ID Parameters Option This specification introduces a new option, the Crypto-ID Parameters Option (CIPO), that carries the proof of ownership of a crypto-ID. 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 | Crypto Type | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + Modifier (16 octets) + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + Subnet Prefix (8 octets) + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | | + Public Key (variable length) + | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | . . . Padding . . . | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: Crypto-ID Parameters Option Type: CIPO, to be assigned by IANA. Length: The length of the option in units of 8 octets. Pad Length: The length of the Padding field. Crypto Type: The type of cryptographic algorithm used in calculation Crypto-ID. Default value of all zeros indicate NIST P-256. A value of 1 is assigned forCurve 25519.Curve25519. New values may be defined later. Modifier: 128 bit random value. Subnet Prefix: 64 bit subnet prefix. Public Key: ECC public key of 6LN. Padding: A variable-length field making the option length a multiple of 8, containing as many octets as specified in the Pad Length field. 5. Protocol Overview 5.1. Protocol Scope The scope of the present work is a 6LoWPAN Low Power Lossy Network (LLN), typically a stub network connected to a larger IP network via a Border Router called a 6LBR per [RFC6775]. The 6LBR maintains a registration state for all devices in the attached LLN, and, in conjunction with the first-hop router (the 6LR), is in a position to validate uniqueness and grant ownership of an IPv6 address before it can be used in the LLN. This is a fundamental difference with a classical network that relies on IPv6 address auto-configuration [RFC4862], where there is no guarantee of ownership from the network, and any IPv6 Neighbor Discovery packet must be individually secured [RFC3971]. ---+-------- ............ | External Network | +-----+ | | 6LBR +-----+ o o o o o o o o o LLN o o o o o o (6LR) o (6LN) Figure 3: Basic Configuration In a mesh network, the 6LR is directly connected to the host device. This specification expects that the peer-wise layer-2 security is deployed so that all the packets from a particular host are securely identifiable by the 6LR. The 6LR may be multiple hops away from the 6LBR. Packets are routed between the 6LR and the 6LBR via other 6LRs. This specification expects that a chain of trust is established so that a packet that was validated by the first 6LR can be safely routed by the next 6LRs to the 6LBR. 5.2. Protocol FlowsThe 6TiSCH Architecture [I-D.ietf-6tisch-architecture] suggests to use of RPL [RFC6550] as the routing protocol between the 6LRs and the 6LBR. In that model,Figure 4 illustrates a registration flowhappens as shown in Figure 4. 6LoWPAN Node 6LR 6LBR (RPL leaf) (router) (RPL root) | | | | 6LoWPAN ND | 6LoWPAN ND | | | | | | | | NS(ARO) | | |-------------->| | | 6LoWPAN ND | DAR | | |-------------->| | |(then RPL DAO) | | | | | | DAC | | |<--------------| | NA(ARO) | | |<--------------| | | | | | | | Figure 4: (Re-)Registration Flowall the way to a 6LowPAN Backbone Router (6BBR). A new device that joins the network auto-configures an address and performs an initial registration to an on-link 6LR with an NS message that carries an Address Registration Option(ARO)(EARO) [RFC6775]. The 6LR validates the address with the central 6LBR using a DAR/DAC exchange, and the 6LR confirms (or denies) the address ownership with an NA message that also carries an Address Registration Option. In a multihop 6LoWPAN, the registration with Crypto-ID is propagated to 6LBR as described in Section 5.3. If a chain of trust is present between the 6LR and the 6LBR, then there is no need to propagate the proof of ownership to the 6LBR. All the 6LBR needs to know is that this particular OUID is randomly generated, so as to enforce that any update via a different 6LR is also random.Local or on-link6LN 6LR 6LBR 6BBR | | | | | NS(EARO) | | | |--------------->| | | | | Extended DAR | | | |-------------->| | | | | | | | | proxy NS(EARO) | | | |--------------->| | | | | NS(DAD) | | | | ------> | | | | | | | | <wait> | | | | | | | proxy NA(EARO) | | | |<---------------| | | Extended DAC | | | |<--------------| | | NA(EARO) | | | |<---------------| | | | | | | Figure 4: (Re-)Registration Flow On-link (local) protocol interactions are shown in Figure 5.Crypto-IDCrypto- ID and ARO are passed to and stored by the6LR/6LBR6LR on the first NS and not sent again in the next NS. The operation starts with 6LR sending a Router Advertisement (RA) message to 6LN. The 6LR/6LBR ensures first-come/first-serve by storing the ARO and the Crypto-ID correlated to the node being registered. The node is free to claim any address it likes as long as it is the first to make such a claim. After a successful registration, the node becomes the owner of the registered address and the address is bound to the Crypto-ID in the 6LR/6LBR registry. This binding can be verified later, which prevents other nodes from stealing the address and trying to attract traffic for that address or use it as their source address. A node mayusesuse multiple IPv6 addresses atany time. This condition may happen for privacy reasons [I-D.ietf-6man-ipv6-address-generation-privacy], or when the node moves at a different place and auto-configures an new address from a different prefix. In those situations,the same time. The node may use the same Crypto-ID to protect multiple IPv6 addresses. The separation of the address and the Crypto-ID avoids the constrained device to compute multiple keys for multiple addresses. The registration process allows the node totiebind all of its addresses to the sameCrypto-ID and have the 6LR/6LBR enforce first-come first-serve after that.Crypto-ID. 6LN 6LR | | |<------------------- RA --------------------------| | | |----------- NS with ARO and Crypto-ID ----------->| | | |<---------- NA with ARO (status=proof requested) -| | | |----------- NS with ARO and Crypto-ID ----------->| | | |<---------------- NA with ARO --------------------| | | ... ... | | |------------ NS with ARO and Crypto-ID ---------->| | | | | |<---------------- NA with ARO --------------------| ... ... | | |----------- NS with ARO and Crypto-ID ----------->| | | | | |<---------------- NA with ARO --------------------| Figure 5: On-link Protocol Operation 5.3. Multihop Operation In a multihop 6LoWPAN, a 6LBR sends RAs with prefixes downstream andit isthe 6LRthatreceives and relays them to the nodes. 6LR and 6LBR communicatewith theusing ICMPv6 Duplicate Address Request (DAR) andtheDuplicate Address Confirmation (DAC) messages. The DAR and DAC use the same message format as NS andNA withNA, but have different ICMPv6 type values. In ND-PAR we extend DAR/DAC messages to carry cryptographically generated OUID. In a multihop 6LoWPAN, the node exchanges the messages shown in Figure 4. The 6LBR mustbe aware ofidentify who owns an address (EUI-64) to defendthe first nodeit, if there is an attacker on another 6LR. Because of this the content that the source signs and the signature needs to be propagated to the 6LBR in the DAR message. For this purpose the DAR message sent by 6LR to 6LBR MUST contain the CIPO option. The DAR message also contains ARO.It is possible that occasionally,Occasionally, a 6LRmaymight miss the node's OUID (that it received in ARO). 6LR should be able to ask for it again. This is done by restarting the exchanges shown in Figure 5. The result enables 6LR to refresh the information that was lost. The 6LR MUST send DAR message with ARO to 6LBR. The 6LBRas a reply formsreplies with a DAC message with the information copied from theDARDAR, and the Status field is set to zero. With this exchange, the 6LBR can (re)validate and store the information to make sure that the 6LR is not a fake. In somecasescases, the 6LBR may use a DAC message tosignal to 6LR that it expectssolicit a Crypto-ID from a 6LR and alsoasksrequests 6LR to verify the EUI-64 6LR received from 6LN. This may happen when a 6LN node is compromised and a fake node is sending the Crypto-ID as if it is the node'sEUI- 64.EUI-64. Note that the detection in this case can only be done by 6LBR not by 6LR. 6. Security Considerations The observations regarding the threats to theLocal Link Networklocal network in [RFC3971] also apply to this specification.This document inheritsThe threats discussed in 6LoWPAN ND [RFC6775] and its update [I-D.ietf-6lo-rfc6775-update]and addresses the potential attacks related to address stealing and spoofing within a LLN.also apply here. Compared with SeND, this specification saves about 1Kbyte in every NS/NA message. Also, this specification separates the cryptographic identifier from the registered IPv6 address so that a node can have more than one IPv6 address protected by the same cryptographic identifier. SeND forces the IPv6 address to be cryptographic since it integrates the CGA as the IID in the IPv6 address. This specification frees the device to form its addresses in any fashion, so as to enable the classical 6LoWPAN compression which derives IPv6 addresses from Layer-2 addresses, as well as privacy addresses. The threats discussed in Section 9.2 of [RFC3971] are countered by the protocol described in this document as well. Collisions of Owner Unique Interface IDentifier (OUID) (which is the Crypto-ID in this specification) is a possibility that needs to be considered. The formula for calculating the probability of a collision is 1 -e^{-k^2/(2n)}.e^{-k^2/(2n)} where n is the maximum population size (2^64 here, 1.84E19) and K is the actual population (number of nodes). If the Crypto-ID is 64-bit long, then the chance of finding a collision is 0.01% when the network contains 66 million nodes. It is important to note that the collision is only relevant when this happens within one stub network (6LBR). A collision ofID in ND-PARCrypto-ID is a rare event.However, when such a collision does happen,In theprotocol operation is not affected, although it opens a window forcase of anode to hijackcollision, anaddress from another. The link-layer security ensures that the nodes would normally notattacker may beaware of a collision on the subnet. If a malicious node isable togain knowledgeclaim the registered address ofa collision through other means,an another legitimate node. However for this to happen, theonly thing that it could do isattacker would also need tosteal addresses fromknow theother honestaddress which was registered by the legitimate node. Thiswould be no different from whatregistered address isalready possible in a 6lohowever never broadcasted on the networktoday.and therefore it provides an additional entropy of 64-bits that an attacker must correctly guess. To prevent such a scenario, it is RECOMMENDED that nodes derive the address being registered independently of the OUID. 7. IANA considerations IANA is requested to assign two new option type values for the CIPO under the subregistry "IPv6 Neighbor Discovery Option Formats". 7.1. Crypto Type Registry The following Crypto Type values are defined in this document: +-------------------+-----------------------------------------+ | Crypto Type value | Algorithms | +-------------------+-----------------------------------------+ | 0 | NIST P-256, SHA-256 [RFC6234] | | 1 | Curve25519 [RFC7748], SHA-256 [RFC6234] | +-------------------+-----------------------------------------+ Table 1: Crypto Types Assignment of new values for new Crypto Type MUST be done through IANA with "Specification Required" and "IESG Approval" as defined in [RFC8126]. 8. Acknowledgements Special thanks to Charlie Perkins for his in-depth review and constructive suggestions. We are also grateful to Rene Struik and Robert Moskowitz for their comments that lead to many improvements to this document. 9. Change Log o submitted version -00 as a working group draft after adoption, and corrected the order of authors o submitted version -01 with no changes o submitted version -02 with these changes: Moved Requirements to Appendix A, Section 4.2 moved to Section 3, New section 4 on New Fields and Options, Section 4 changed to Protocol Overview as Section 5 with Protocol Scope and Flows subsections. o submitted version -03 addressing Charlie Perkins' comments 10. References 10.1. Normative References [I-D.ietf-6lo-rfc6775-update] Thubert, P., Nordmark, E., and S. Chakrabarti, "An Update to 6LoWPAN ND", draft-ietf-6lo-rfc6775-update-09 (work in progress), September 2017. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997,<http://www.rfc-editor.org/info/rfc2119>.<https://www.rfc-editor.org/info/rfc2119>. [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 4291, DOI 10.17487/RFC4291, February 2006,<http://www.rfc-editor.org/info/rfc4291>.<https://www.rfc-editor.org/info/rfc4291>. [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, DOI 10.17487/RFC4861, September 2007,<http://www.rfc-editor.org/info/rfc4861>.<https://www.rfc-editor.org/info/rfc4861>. [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless Address Autoconfiguration", RFC 4862, DOI 10.17487/RFC4862, September 2007,<http://www.rfc-editor.org/info/rfc4862>.<https://www.rfc-editor.org/info/rfc4862>. [RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C. Bormann, "Neighbor Discovery Optimization for IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs)", RFC 6775, DOI 10.17487/RFC6775, November 2012,<http://www.rfc-editor.org/info/rfc6775>. [I-D.ietf-6lo-rfc6775-update]<https://www.rfc-editor.org/info/rfc6775>. 10.2. Informative references [I-D.ietf-6lo-backbone-router] Thubert, P.,Nordmark, E., and S. Chakrabarti, "An Update to 6LoWPAN ND", draft-ietf-6lo-rfc6775-update-05"IPv6 Backbone Router", draft-ietf-6lo- backbone-router-04 (work in progress),MayJuly 2017.10.2. Informative references[RFC3971] Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander, "SEcure Neighbor Discovery (SEND)", RFC 3971, DOI 10.17487/RFC3971, March 2005,<http://www.rfc-editor.org/info/rfc3971>.<https://www.rfc-editor.org/info/rfc3971>. [RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)", RFC 3972, DOI 10.17487/RFC3972, March 2005,<http://www.rfc-editor.org/info/rfc3972>. [RFC4944] Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler, "Transmission of IPv6 Packets over IEEE 802.15.4 Networks", RFC 4944, DOI 10.17487/RFC4944, September 2007, <http://www.rfc-editor.org/info/rfc4944>. [RFC6282] Hui, J., Ed. and P. Thubert, "Compression Format for IPv6 Datagrams over IEEE 802.15.4-Based Networks", RFC 6282, DOI 10.17487/RFC6282, September 2011, <http://www.rfc-editor.org/info/rfc6282>.<https://www.rfc-editor.org/info/rfc3972>. [RFC4919] Kushalnagar, N., Montenegro, G., and C. Schumacher, "IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs): Overview, Assumptions, Problem Statement, and Goals", RFC 4919, DOI 10.17487/RFC4919, August 2007,<http://www.rfc-editor.org/info/rfc4919>.<https://www.rfc-editor.org/info/rfc4919>. [RFC4944] Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler, "Transmission of IPv6 Packets over IEEE 802.15.4 Networks", RFC 4944, DOI 10.17487/RFC4944, September 2007, <https://www.rfc-editor.org/info/rfc4944>. [RFC5889] Baccelli, E., Ed. and M. Townsley, Ed., "IP Addressing Model in Ad Hoc Networks", RFC 5889, DOI 10.17487/RFC5889, September 2010,<http://www.rfc-editor.org/info/rfc5889>.<https://www.rfc-editor.org/info/rfc5889>. [RFC6234] Eastlake 3rd, D. and T. Hansen, "US Secure Hash Algorithms (SHA and SHA-based HMAC and HKDF)", RFC 6234, DOI 10.17487/RFC6234, May 2011,<http://www.rfc-editor.org/info/rfc6234>. [RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A.,<https://www.rfc-editor.org/info/rfc6234>. [RFC6282] Hui, J.,Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur, JP., and R. Alexander, "RPL: IPv6 Routing Protocol for Low-PowerEd. andLossy Networks", RFC 6550, DOI 10.17487/RFC6550, March 2012, <http://www.rfc-editor.org/info/rfc6550>. [RFC7102] Vasseur, JP., "Terms Used in RoutingP. Thubert, "Compression Format forLow-Power and LossyIPv6 Datagrams over IEEE 802.15.4-Based Networks", RFC7102,6282, DOI10.17487/RFC7102, January 2014, <http://www.rfc-editor.org/info/rfc7102>.10.17487/RFC6282, September 2011, <https://www.rfc-editor.org/info/rfc6282>. [RFC7039] Wu, J., Bi, J., Bagnulo, M., Baker, F., and C. Vogt, Ed., "Source Address Validation Improvement (SAVI) Framework", RFC 7039, DOI 10.17487/RFC7039, October 2013,<http://www.rfc-editor.org/info/rfc7039>.<https://www.rfc-editor.org/info/rfc7039>. [RFC7102] Vasseur, JP., "Terms Used in Routing for Low-Power and Lossy Networks", RFC 7102, DOI 10.17487/RFC7102, January 2014, <https://www.rfc-editor.org/info/rfc7102>. [RFC7217] Gont, F., "A Method for Generating Semantically Opaque Interface Identifiers with IPv6 Stateless Address Autoconfiguration (SLAAC)", RFC 7217, DOI 10.17487/RFC7217, April 2014,<http://www.rfc-editor.org/info/rfc7217>.<https://www.rfc-editor.org/info/rfc7217>. [RFC7696] Housley, R., "Guidelines for Cryptographic Algorithm Agility and Selecting Mandatory-to-Implement Algorithms", BCP 201, RFC 7696, DOI 10.17487/RFC7696, November 2015,<http://www.rfc-editor.org/info/rfc7696>.<https://www.rfc-editor.org/info/rfc7696>. [RFC7721] Cooper, A., Gont, F., and D. Thaler, "Security and Privacy Considerations for IPv6 Address Generation Mechanisms", RFC 7721, DOI 10.17487/RFC7721, March 2016, <https://www.rfc-editor.org/info/rfc7721>. [RFC7748] Langley, A., Hamburg, M., and S. Turner, "Elliptic Curves for Security", RFC 7748, DOI 10.17487/RFC7748, January 2016,<http://www.rfc-editor.org/info/rfc7748>. [I-D.ietf-6lo-backbone-router] Thubert, P., "IPv6 Backbone Router", draft-ietf-6lo- backbone-router-03 (work in progress), January 2017. [I-D.ietf-6tisch-architecture] Thubert, P., "An Architecture for IPv6 over the TSCH mode of IEEE 802.15.4", draft-ietf-6tisch-architecture-11 (work in progress), January 2017. [I-D.ietf-6man-ipv6-address-generation-privacy] Cooper, A., Gont, F.,<https://www.rfc-editor.org/info/rfc7748>. [RFC8126] Cotton, M., Leiba, B., andD. Thaler, "Privacy ConsiderationsT. Narten, "Guidelines forIPv6 Address Generation Mechanisms", draft-ietf-6man-ipv6-address-generation-privacy-08 (workWriting an IANA Considerations Section inprogress), September 2015.RFCs", BCP 26, RFC 8126, DOI 10.17487/RFC8126, June 2017, <https://www.rfc-editor.org/info/rfc8126>. Appendix A. Requirements Addressed in this Document In this section we state requirements of a secure neighbor discovery protocol for low-power and lossy networks. o The protocol MUST be based on the Neighbor Discovery Optimization for Low-power and Lossy Networks protocol defined in [RFC6775]. RFC6775 utilizes optimizations such as host-initiated interactions for sleeping resource-constrained hosts and elimination of multicast address resolution. o New options to be added to Neighbor Solicitation messages MUST lead to small packet sizes, especially compared with existing protocols such as SEcure Neighbor Discovery (SEND). Smaller packet sizes facilitate low-power transmission by resource- constrained nodes on lossy links. o The support for this registration mechanism SHOULD be extensible to more LLN links than IEEE 802.15.4 only. Support for at least the LLN links for which a 6lo "IPv6 over foo" specification exists, as well as Low-Power Wi-Fi SHOULD be possible. o As part of this extension, a mechanism to compute a unique Identifier should be provided with the capability to form a Link Local Address that SHOULD be unique at least within the LLN connected to a 6LBR. o The Address Registration Option used in the ND registration SHOULD be extended to carry the relevant forms of Unique Interface IDentifier. o The Neighbour Discovery should specify the formation of a site- local address that follows the security recommendations from [RFC7217]. Authors' Addresses Behcet SarikayaHuawei USA 5340 Legacy Dr. Building 3Plano, TX75024USA Email: sarikaya@ieee.org Pascal Thubert Cisco Systems, Inc Building D 45 Allee des Ormes - BP1200 MOUGINS - Sophia Antipolis 06254 FRANCE Phone: +33 497 23 26 34 Email: pthubert@cisco.com Mohit Sethi Ericsson Hirsalantie Jorvas 02420 Email: mohit@piuha.net