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Rationale for Public Key Security in 802.15.3

This document highlights the impact of and lacking rationale for the removal of public key security from the 802.15.3 draft, raising awareness of limited remaining security provisions in Draft D16.

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Rationale for Public Key Security in 802.15.3

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  1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [Rationale for Public Key Security in 802.15.3] Date Submitted: [12 March, 2003] Source: [Rene Struik] Company [Certicom Corp.] Address [5520 Explorer Drive, 4th Floor, Mississauga, ON Canada L4W 5L1] Voice:[+1 (905) 501-6083], FAX: [+1 (905) 507-4230], E-Mail:[rstruik@certicom.com] Re: [03/054r1] Abstract: [This document discusses the impact of and lacking rationale for the removal of public key security from the 802.15.3 draft during Sponsor Ballot comment resolution (of Draft D15) at the IEEE 802 Interim Meeting in Ft. Lauderdale (January 13-17, 2003).] Purpose: [Highlight major changes in 802.15.3 WPAN security, inconsistencies in approach within the IEEE 802.15.3 WPAN task group and between different IEEE 802 groups. Raise awareness in 802.15.3 and 802.15.3a community of limited remaining security provisions in Draft D16.] Notice: This document has been prepared to assist the IEEE P802.15. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P802.15. Rene Struik, Certicom Corp.

  2. Rationale for Public Key SecurityinIEEE 802.15.3(a) WPANs René Struik, Certicom Research Rene Struik, Certicom Corp.

  3. Outline • WPAN Network Security • Security Changes to the 802.15.3 Specification • – Impact on 802.15.3(a) • – Rationale (?) • — • ANNEX A Rene Struik, Certicom Corp.

  4. WPAN Network Security (1) • Access control to the piconet itself • Restriction of access to scarce network resources to authorized devices only, to • ensure objectives including the following: • - proper bandwidth allocation; • - protection of commands (e.g., those regulating network membership); • - power drain savings. • Control of access to message traffic between piconet devices • Restriction of access to information secured between members of a group of WPAN • devices to precisely these group members. This includes any of the following • objectives: • - Confidentiality. • Prevent external parties from learning the content of exchanged messages. • - Data integrity/message authentication. • Prevent external parties from modifying or injecting messages in undetected way. Rene Struik, Certicom Corp.

  5. PNC A A WPAN Network Security (2) • Access control to the piconet itself • Restriction of access to scarce network resources to authorized devices only, to • ensure objectives including the following: • - proper bandwidth allocation; • - protection of commands (e.g., those regulating network membership); • - power drain savings. piconet Authorization: Authentication + Membership test (ACL) (side-effect: shared link key A – PNC) PNC enlarged piconet Public key techniques, since ad-hoc, spontaneous network Rene Struik, Certicom Corp.

  6. C A B B A PNC WPAN Network Security (3) • Control of access to message traffic between Network devices • Restriction of access to information secured between members of a group of WPAN • devices to precisely these group members. This includes any of the following • objectives: • - Confidentiality. • Prevent external parties from learning the content of exchanged messages. • - Data integrity/message authentication. • Prevent external parties from modifying or injecting messages in undetected way. Key transport: distribution of keys to devices Peer-to-peer security: Data: Encryption + Integrity Commands: Integrity PNC Broadcast security: Data: Encryption + Integrity Beacons: Integrity D Rene Struik, Certicom Corp.

  7. PNC A A WPAN Network Security (4) • Access control to the piconet itself • Restriction of access to scarce network resources to authorized devices only, to • ensure objectives including the following: • - proper bandwidth allocation; • - protection of commands (e.g., those regulating network membership); • - power drain savings. Draft D15  D16: ‘Public key Exorcism (03/054r1)’ piconet Declared Out of scope Authorization: Authentication + Membership test (ACL) (side-effect: shared link key A – PNC) PNC enlarged piconet Public key techniques, since ad-hoc, spontaneous network Rene Struik, Certicom Corp.

  8. C A B B A PNC WPAN Network Security (5) • Control of access to message traffic between Network devices • Restriction of access to information secured between members of a group of WPAN • devices to precisely these group members. This includes any of the following • objectives: • - Confidentiality. • Prevent external parties from learning the content of exchanged messages. • - Data integrity/message authentication. • Prevent external parties from modifying or injecting messages in undetected way. Key transport: distribution of keys to devices Peer-to-peer security: Data: Encryption + Integrity Commands: Integrity Draft D15  D16: No changes PNC Broadcast security: Data: Encryption + Integrity Beacons: Integrity D Rene Struik, Certicom Corp.

  9. Security Changes to 802.15.3 Specification (1) • Impact of Security Changes Draft D15  D16 • NO mechanism left for device authentication in 802.15.3 specification • REMAINS: mechanism for key updates and secure data transport • Inconsistent: key transport left in, key agreement left out (conceptually the same) • Consequences: • IEEE 802.15.3(a) WPANs: no secure piconet access mechanism specified • (since 802.15.3 MAC re-used for 802.15.3a) • Lack of interoperability between devices • Uncertainty about secure operation of networks • Severe impact on: • - time-to-market (someone else has to define authentication now) • - market size (no interoperability, so no ‘network effects’) • - industry acceptance • In short: Change sacrifices secure piconet operation (what is rationale?) Rene Struik, Certicom Corp.

  10. Security Changes to 802.15.3 Specification (2) • Rationale Security Changes Draft D15  D16 (according to 03/054r1) • ‘Paul Nikolich felt authentication to be out of scope’ • Comments: • Opinion expressed as 802 member, not as Chair IEEE 802 • Opinion poorly interpreted by 802.15.3 Chair: • - ‘security suites out of scope’  authentication for higher layers • - ‘to be discussed at March Plenary’  premature removal authentication • (put process in place to solve issue) • - options: remains within WG, LinkSec, or 802.1  1 option: removal • Opinion inconsistent with practices elsewhere in IEEE 802 standards (see Annex A) • Improper use of Sponsor Ballot comments (CID #19, Dan Bailey): • - (speculation) Comment based on ‘yet another break of NTRUEncrypt’ • Insufficient discussion about alternative means for solving authentication problem: • - 802.1x mechanism: in ‘adhoc’ network to be integrated with each device!! • - LinkSec ECSG will solve this: just formed, composed of people alien to • WPAN requirements, no desire to solve WPAN problems (mainly Ethernet) • - Industry consortium will solve this: timeline?? • Uncertainty about secure operation of networks • Severe impact on: • - time-to-market (someone else has to define authentication now) • - market size (no interoperability, so no ‘network effects’) • - industry acceptance • In short: Change sacrifices secure piconet operation (what is rationale?) Rene Struik, Certicom Corp.

  11. ANNEX A • Security Architectural Framework • Partitioning within various IEEE 802 Standards • – IEEE 802.11 WLAN • – IEEE 802.15.4 WPAN • – IEEE 802.15.3 WPAN (Draft D15) • – IEEE 802.15.3 WPAN (Draft D16) Rene Struik, Certicom Corp.

  12. Security Architectural Framework Rene Struik, Certicom Corp.

  13. Outline • Overview • Key Establishment • Key Transport • Data Transport Rene Struik, Certicom Corp.

  14. Security Architectural Framework: Overview (1) • Security mechanisms: • Public-key or symmetric-key key establishment mechanism. Derivation of link • key between two devices, based on authentic public keys or symmetric keys of • both parties, including evidence on whom this link key is shared with. • Symmetric-key key transport mechanism. Secure transfer of data key from • one device to other(s), based on link key(s) between sender and recipient(s). • Symmetric-key data transfer mechanism(s). Secure and/or authentic data transfer • between devices that share the data key (confidentiality/data integrity/authenticity). • Security policy: • … • Note: Security mechanisms 1 and 2 may be combined (distinction based on • implementation cost considerations only). Rene Struik, Certicom Corp.

  15. ACL initialization ACL initialization ACL ACL Public key verification Public key verification Encryptor/ decryptor Encryptor/ decryptor Data key repository Wrapped public key info B A ACL Maintenance Data key maintenance Certificate maintenance ACL Maintenance Certificate maintenance Extracted public key info CA key initialization CA key initialization Authentication, key establishment data transfer key distribution (Link key, A, B) (Link key, A, B) Other Key Management Wrapped public key info Other Key Management A B A B Wrapped data key info Wrapped data key info Data key maintenance Data key repository Extracted public key info Key info Data key Data key Key info Key Usage Key Usage data data Wrapped data Wrapped data Security Architectural Framework: Overview (2) Rene Struik, Certicom Corp.

  16. Security Architectural Framework: Authorization (1) • Authorization and key establishment is based on each of the following: • Evidence regarding the true identity of the other device; • Evidence whether one wants to communicate with this explicitly identified • device. • Cryptographic mechanisms: • Public-key key establishment mechanism. Derivation of link key between • two devices, based on authentic public keys of both parties, including • evidence on whom this link key is shared with. • Symmetric-key key establishment mechanism. Derivation of link key between • two devices, based on secret and authentic pre-shared key between both parties, • including evidence on whom this link key is shared with. • Non-cryptographic mechanisms: • Acceptability test. Establishment whether a particular device is to be accepted, • based on a membership test of a so-called Access Control List (ACL). Rene Struik, Certicom Corp.

  17. ACL initialization ACL initialization Public key verification Public key verification ACL ACL Wrapped public key info ACL Maintenance ACL Maintenance Certificate maintenance Certificate maintenance B A CA key initialization CA key initialization Authentication, key establishment Extracted public key info Wrapped public key info (Link key, A, B) (Link key, A, B) Extracted public key info Security Architectural Framework: Authorization (2a) (public-key scenario) • Notes: • - The authentication protocol establishes a symmetric link key between the devices • (since it is an authenticated key establishment protocol). • Authenticated key establishment is based on a specific public-key protocol (e.g., • ECC-based), using manual, explicit (e.g., X509), or implicit certificates. • - Certificate maintenance and ACL maintenance are not discussed any further here. Rene Struik, Certicom Corp.

  18. ACL initialization ACL initialization ACL Maintenance ACL Maintenance ACL ACL Symm. key initialization Symm. key initialization Symmetric key info Symmetric key info Symmetric-key maintenance Symmetric-key maintenance Symm. key verification Symm. key verification B A Authentication, key establishment Extracted symmetric key Extracted symmetric key (Link key, A, B) (Link key, A, B) Security Architectural Framework: Authorization (2b) (symmetric-key scenario) Notes: - The authentication protocol establishes a symmetric link key between the devices (since it is an authenticated key establishment protocol). - Authenticated key establishment is based on a specific symmetric-key protocol, using pre-shared secret keys. - Symmetric-key maintenance and ACL maintenance are not discussed any further here. Rene Struik, Certicom Corp.

  19. Security Architectural Framework: Key transport (1) • Key transport is based on each of the following: • Availability of a shared link key with the recipient; • Evidence whether one wants to communicate with this explicitly identified • device. • Cryptographic mechanisms: • 1. Symmetric-key key transport mechanism. Secure transfer of data key from • one device to other(s), based on link key(s) between sender and recipient(s). Rene Struik, Certicom Corp.

  20. Data key repository (Link key, A, B) (Link key, A, B) Data key repository Wrapped data key info Wrapped data key info Data key maintenance Data key maintenance key distribution A B Security Architectural Framework: Key transport (2) Notes: -Authenticated key transport may be based on the data protection mode that yields both confidentiality and authenticity. - Key transport must include authentic info on, e.g., the key originator, the distribution group (key-sharing parties), and the version of the key. (The string Key Id:=(Key originator || KeySeqNo) seems to be a good choice.) - Key storage and key update mechanisms are not discussed any further here. Rene Struik, Certicom Corp.

  21. Security Architectural Framework: Data transport (1) • Data transport is based on each of the following: • Availability of a shared data key with the recipient(s); • Evidence whether one wants to communicate with this explicitly identified • device. • Cryptographic mechanisms: • 1. Data transfer mechanism(s). Secure and/or authentic data transfer between • devices that share the data key (confidentiality/data integrity/authenticity). Rene Struik, Certicom Corp.

  22. Data key repository Encryptor/ decryptor Encryptor/ decryptor Data key repository Key info Data key Data key Key info Wrapped data Wrapped data data transfer A B data data Security Architectural Framework: Data transport (2) Notes: - Data transport may be based on any negotiated data protection mode that yields a combination of confidentiality and authenticity (for predefined taxonomy) - Data transport must include authentic info on, e.g., the used data key(s), the sender, and a message sequence number (to prevent replay attacks). Rene Struik, Certicom Corp.

  23. Security Architectural Framework – Partitioning within various IEEE 802 standards Rene Struik, Certicom Corp.

  24. Outline • IEEE 802.11 WLAN • IEEE 802.15.4 WPAN • IEEE 802.15.3 WPAN Rene Struik, Certicom Corp.

  25. Symm. key verification Symm. key verification Encryptor/ decryptor Encryptor/ decryptor Data key repository External External IEEE 802.11 IEEE 802.11 Symmetric-key maintenance ACL Maintenance Data key maintenance Symmetric-key maintenance ACL Maintenance Symmetric key initialization Symmetric key initialization Authentication, key establishment data transfer key distribution Symmetric key info A B A B Extracted Symmetric key data data Security Architectural Framework: 802.11 WLAN (1) ACL initialization ACL initialization ACL ACL Symmetric key info B A Extracted Symmetric key (Link key, A, B) (Link key, A, B) Other Key Management Other Key Management Wrapped data key info Wrapped data key info Data key maintenance Data key repository Key info Data key Data key Key info Key Usage Key Usage Wrapped data Wrapped data Rene Struik, Certicom Corp.

  26. ACL initialization ACL initialization ACL ACL Public key verification Public key verification Encryptor/ decryptor Encryptor/ decryptor Data key repository Wrapped public key info B A ACL Maintenance Data key maintenance Certificate maintenance ACL Maintenance Certificate maintenance Extracted public key info CA key initialization CA key initialization External: IEEE 802.1x External: IEEE 802.1x Authentication, key establishment data transfer key distribution IEEE 802.11 IEEE 802.11 (Link key, A, B) (Link key, A, B) Other Key Management Wrapped public key info Other Key Management A B A B Wrapped data key info Wrapped data key info Data key maintenance Data key repository Extracted public key info Key info Data key Data key Key info Key Usage Key Usage data data Wrapped data Wrapped data Security Architectural Framework: 802.11 WLAN (2) Rene Struik, Certicom Corp.

  27. Public key verification Public key verification Encryptor/ decryptor Encryptor/ decryptor Data key repository ACL Maintenance Certificate maintenance Data key maintenance ACL Maintenance Certificate maintenance CA key initialization CA key initialization Authentication, key establishment data transfer key distribution Wrapped public key info A B A B Extracted public key info data data Security Architectural Framework: 802.15.4 WPAN ACL initialization ACL initialization ACL ACL Wrapped public key info B A Extracted public key info External (e.g., ZigBee) External (e.g., ZigBee) (Link key, A, B) (Link key, A, B) Other Key Management Other Key Management IEEE 802.15.4 IEEE 802.15.4 Wrapped data key info Wrapped data key info Data key maintenance Data key repository Key info Data key Data key Key info Key Usage Key Usage Wrapped data Wrapped data Rene Struik, Certicom Corp.

  28. ACL initialization ACL initialization ACL ACL Public key verification Public key verification Encryptor/ decryptor Encryptor/ decryptor Data key repository Wrapped public key info B A ACL Maintenance Certificate maintenance Data key maintenance ACL Maintenance Certificate maintenance Extracted public key info CA key initialization CA key initialization Authentication, key establishment data transfer key distribution (Link key, A, B) (Link key, A, B) Other Key Management Wrapped public key info Other Key Management A B A B Wrapped data key info Wrapped data key info Data key maintenance Data key repository Extracted public key info Key info Data key Data key Key info Key Usage Key Usage data data Wrapped data Wrapped data Security Architectural Framework: 802.15.3 WPAN (1) Pre-‘Exorcism’ Situation External External IEEE 802.15.3 IEEE 802.15.3 Rene Struik, Certicom Corp.

  29. ACL initialization ACL initialization ACL ACL Public key verification Public key verification Encryptor/ decryptor Encryptor/ decryptor Data key repository Wrapped public key info B A ACL Maintenance Certificate maintenance Data key maintenance ACL Maintenance Certificate maintenance Extracted public key info CA key initialization CA key initialization Authentication, key establishment data transfer key distribution (Link key, A, B) (Link key, A, B) Other Key Management Wrapped public key info Other Key Management A B A B Wrapped data key info Wrapped data key info Data key maintenance Data key repository Extracted public key info Key info Data key Data key Key info Key Usage Key Usage data data Wrapped data Wrapped data Security Architectural Framework: 802.15.3 WPAN (2) Post-‘Exorcism’ Situation Unknown! Unknown! IEEE 802.15.3 IEEE 802.15.3 Rene Struik, Certicom Corp.

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