An Efficient On-line Electronic Cash with Unlinkable Exact Payments：一个有效的和不精确的离线电子现金支付.pptVIP

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2018-06-24 发布于四川
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An Efficient On-line Electronic Cash with Unlinkable Exact Payments：一个有效的和不精确的离线电子现金支付.ppt

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An Efficient On-line Electronic Cash with Unlinkable Exact Payments：一个有效的和不精确的离线电子现金支付

WISA2003 An Efficient On-line Electronic Cash with Unlinkable Exact Payments Toru Nakanishi, Mitsuaki Shiota and Yuji Sugiyama Dept. of Communication Network Engineering, Okayama Univ., Japan Requirements Previous work On-line system [3] with unlinkable exact payments User anonymously obtains changes Problems of [3] Assume there are coin types with all payable amounts( e.g.,￠1 coin type ～　$1,000 coin type) A payment T1 Another payment T2 Use a coin with $27.46 Problems of [3] (Cont.) Assume there are coin types with amounts 2i (1, 2, 4, 8, …) N : the number of payable amounts Then, to express any amount, O(log N) coins needed In case of N=100,000(￠1 ～　$1,000), 17 coins Protocol [3] needs about10 multi-exp’s per a coin Total cost of a payment is more than 100 multi-exp’s Our contributions On-line e-cash with unlinkable exact payments satisfying both efficiency and unlinkability A payment needs only 1 coin 　→ Efficient Coin amounts are kept secret → Protect linking via coin amounts Our approach Use changes A coin is assigned to any amount Every coin amount is kept secret, but correctness of amounts of old and new coins is ensured by a ZPK (Zero-knowledge Proof of Knowledge) Used tool:Camenisch-Lysyanskaya signature scheme[4] RSA type Multiple messages signed A coin : Sign(x,m) w.r.t. Bank’s key x: a secret of user, m: coin amount Protocols in [4] A ZPK of ownership of Sign(x,m) without revealing Sign(x,m), x, m A protocol to sign, where x, m are kept secret for the signer Idea of our system (unlinkability correctness in payment) Payment of $p Conclusion Efficient on-line e-cash with unlinkable exact payments O(1) efficiency w.r.t. N In detail, about 20 multi-exp’s in a payment Future works Strict security considerations Further efficiency improvements * * What’s on-line e-cash ? Bank User Withdrawal Coins of amounts w Payment for a merchant User’s account -w User Bank Coins of amounts p Merchant’s account +p e-cash: By circulat