Divisible Digital Cash Via Secret Sharing Schemes
| dc.contributor.author | Yip, Wai Kuan | |
| dc.date.accessioned | 2017-09-29T02:11:15Z | |
| dc.date.available | 2017-09-29T02:11:15Z | |
| dc.date.issued | 2002-08 | |
| dc.description.abstract | Digital cash describes a class of cryptographically secure and transactionally anonymous payment protocols featuring exchange of a data structure-thereafter referred to as a Coin-which can be employed as a medium of exchange/store of value analogous to physical currency. It would minimally be required to support offline (Coin authenticity is verifiable without Merchant-Bank connectivity) and conditionally anonymous payment (the User's identity is untraceable until he commits a fraudulent payment). However, Coin creation is typically processor and storage/bandwidth intensive, hence the motivation for aggregating a withdrawal single episode over multiple independent payment units or sub-Coins. Such digital cash schemes are said to be divisible, which has no physical analogue given that a broken-off piece of physical currency is not considered valid. Various divisible cash protocols based on the nested computation of modular ยท quadratic residues (QR)-resulting in binary tree-like Coin structures-have been formulated, and - have been demonstrated to be both theoretically elegant and computationally efficient. On the other hand, their divisibility is based on successive binary exponentiations and would therefore be transactionally awkward within the context of a decimal currency system. This thesis demonstrates the incorporation of transactionally flexible k-divisibility into the Brands single-term scheme by application of Shamir secret sharing (SS), and Feldman (1987) and Pedersen ( 1991) verifiable SS (VSS), which are respectively based on modular polynomial interpolation and the discrete logarithmic (DL) protected analogue thereof. The purely DL nature of the featured scheme contrasts with Okamoto's original tree-based scheme-which can itself be considered to be a functional extension of the seminal Chaum digital cash-and with the Chan-Frankel-Tsiounis composite construction of tree-like Coins within a fundamentally DL Brands framework. This allows for an elliptic curve (EC) DL (ECDL) implementation; which invariably reduces processor, storage and bandwidth overheads by a significant degree when deployed as a straightforward replacement of a integer-field DL analogue. The experimental data, in fact, indicates that the featured scheme would be more efficient than tree-based schemes (for a comparable degree of security) for up to k -10, which would be adequate for most practical applications. The dramatically reduced storage and bandwidth overhead also opens-up the possibility of implementation on lightweight platforms i.e. smartcards and Personal Digital Assistants (PDA). We demonstrate that a transactional solution featuring polynomial-divided sub-Coins in conjunction with a small number of Coin denominations can be implemented so as to be comparable in efficiency to a theoretically-optimal tree-based scheme. The thesis demonstrates a provisional solution featuring a constraint-based sub-Coin dispenser to compute exact User-to-Merchant payment or Merchant-to-User change, which would be useful and straightforwardly integratable into a Coin-processing purse application. | en_US |
| dc.identifier.uri | http://hdl.handle.net/123456789/4756 | |
| dc.language.iso | en | en_US |
| dc.publisher | Universiti Sains Malaysia | en_US |
| dc.subject | Divisible digital cash via | en_US |
| dc.subject | via secret sharing schemes | en_US |
| dc.title | Divisible Digital Cash Via Secret Sharing Schemes | en_US |
| dc.type | Thesis | en_US |
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