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Understanding iKP Protocol: A Detailed Overview and Comparison of 1KP, 2KP, and 3KP

Learn about i-Key Protocol (iKP), its history, party requirements, protocol components, and detailed protocol flow. Compare iKP variants (1KP, 2KP, 3KP) and their key features. Explore the differences and benefits for secure electronic payments.

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Understanding iKP Protocol: A Detailed Overview and Comparison of 1KP, 2KP, and 3KP

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  1. iKP: i-Key-Protocol Christopher Hsu

  2. What is iKP? • i-Key-Protocol, i = 1, 2, 3, … • Family of protocols • Secure electronic payment • Based on credit card payments • Can be extended to debit card and check payments

  3. History of iKP • 1995, IBM Research Labs Zurich and Watson Research Centre • Open industry standard • Incorporated into SEPP, SET • ZiP: fully operational prototype • Did not become commercial product • But has been deployed in some businesses

  4. Initial Assumptions • Only partial privacy is emphasized • Encryption not used in protocol • Can be implemented by other means • Or protocol can be extended • iKP emphasizes the payment • Assumes purchase order is already known

  5. Parties and Attackers • Three parties: Acquirer (A), Merchant (M), Customer (C) • Three attackers: eavesdropper, active attacker, insider

  6. Acquirer Requirements • A1. Proof of transaction authorization of customer • A2. Proof of transaction authorization by merchant

  7. Merchant Requirements • M1. Proof of transaction authorization by acquirer • M2. Proof of transaction authorization by customer

  8. Customer Requirements • C1. Unauthorized payment is impossible • C2. Proof of transaction authorization by acquirer • C3. Certification and authentication of merchant • C4. Receipt from merchant

  9. Extra Customer Requirements • C5. Privacy • C6. Anonymity

  10. Components of the Protocol • Keys: PKX, SKX, CERTX • Cryptography: H(.), EX(.), SX(.) • Quantities: SALTC, PRICE, DATE, NONCEM, IDM, TIDM, DESC, CAN, RC, CID, Y/N, PIN, V • Discuss 1KP in detail, comparison with 2KP and 3KP

  11. Initiate: CM Invoice: CM Payment: CM Auth-Request: MA Auth-Response: MA Confirm: CM SALTC, CID Clear EncSlip Clear, H(DESC,SALTC), EncSlip Y/N, SigA Y/N, SigA 1KP Protocol Flow Common: PRICE, IDM, TIDM, DATE, NONCEM, CID, H(DESC,SALTC) Clear: IDM, TIDM, DATE, NONCEM, H(Common) SLIP: PRICE, H(Common), CAN, RC, [PIN] EncSlip: EA(SLIP) SigA: SA(Y/N, H(Common))

  12. Initiate: CM Invoice: CM Payment: CM Auth-Request: MA Auth-Response: MA Confirm: CM SALTC, CID Clear EncSlip* Clear, H(DESC,SALTC), EncSlip* Y/N, SigA Y/N, SigA Removing Nonce and Date Common: PRICE, IDM, TIDM, DATE, NONCEM, CID, H(DESC,SALTC) Clear: IDM, TIDM, DATE, NONCEM, H(Common) SLIP: PRICE, H(Common), CAN, RC, [PIN] EncSlip: EA(SLIP) SigA: SA(Y/N, H(Common))

  13. Initiate: CM Invoice: CM Payment: CM Auth-Request: MA Auth-Response: MA Confirm: CM SALTC, CID Clear EncSlip Clear, H(DESC,SALTC), EncSlip Y/N, SigA Y/N, SigA Removing SALTC Common: PRICE, IDM, TIDM, DATE, NONCEM, CID, H(DESC,SALTC) Clear: IDM, TIDM, DATE, NONCEM, H(Common) SLIP: PRICE, H(Common), CAN, RC, [PIN] EncSlip: EA(SLIP) SigA: SA(Y/N, H(Common))

  14. Removing SALTC: Invariant -- Intruder never knows desc and salt from same customer invariant "Intruder does not know DESC" forall i: IntruderId do forall j: CustomerId do !int[i].descs[j] | !int[i].salts[j] end end;

  15. What is not fulfilled? • Acquirer’s proof of transaction authorization by merchant • Merchant’s proof of transaction authorization by customer • Customer’s certification and authentication of merchant • Customer’s receipt from merchant

  16. 2KP and 3KP • Satisfies deficiencies of 1KP • Differs in the number of public keys available • Guarantees more undeniable receipts for the transaction

  17. Initiate: CM Invoice: CM Payment: CM Auth-Request: MA Auth-Response: MA Confirm: CM SALTC, CID Clear, SigM, CERTM EncSlip Clear, H(DESC,SALTC), EncSlip, SigM, CERTM Y/N, SigA Y/N, V, SigA 2KP Protocol Flow Common: PRICE, IDM, TIDM, DATE, NONCEM, CID, H(DESC,SALTC), H(V) Clear: IDM, TIDM, DATE, NONCEM, H(V), H(Common) SLIP: PRICE, H(Common), CAN, RC EncSlip: EA(SLIP) SigA: SA(Y/N, H(Common)) SigM: SM(H(Common), H(V))

  18. 2KP Additions • Merchant has public/private key and certificate • Acquirer has certification and authentication of merchant • Customer has certification and authentication of merchant • Customer has receipt from merchant

  19. Initiate: CM Invoice: CM Payment: CM Auth-Request: MA Auth-Response: MA Confirm: CM SALTC, CID, CERTC Clear, SigM EncSlip, SigC Clear, H(DESC,SALTC), EncSlip, SigM, SigC Y/N, SigA Y/N, V, SigA 3KP Protocol Flow Common: PRICE, IDM, TIDM, DATE, NONCEM, CID, H(DESC,SALTC), H(V) Clear: IDM, TIDM, DATE, NONCEM, H(V), H(Common) SLIP: PRICE, H(Common), CAN, RC EncSlip: EA(SLIP) SigA: SA(Y/N, H(Common)) SigM: SM(H(Common), H(V)) SigC: SC(EncSlip, H(Common))

  20. 3KP Additions • Customer has public/private key and certificate • Merchant has proof of transaction authorization by customer

  21. iKP Comparison Overview

  22. iKP Summary • 1KP: simple, merchant is not authenticated, order and receipt are deniable • 2KP: merchant is authenticated • 3KP: non-repudiation for all messages • Intended for gradual deployment

  23. Bibliography • Bellare, Mihir et al. Design, Implementation and Deployment of the iKP Secure Electronic Payment System. IEEE Journal of Selected Areas in Communications, VOL 18, NO. 4, April 2000. • Bellare, Mihir et al. iKP – A Family of Secure Electronic Payment Protocols. 1995.

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