Solutions to Security Problems of Rivest and Shamir's PayWord Scheme

Norio ADACHI; Satoshi AOKI; Yuichi KOMANO; Kazuo OHTA

doi:10.1093/ietfec/e88-a.1.195

Solutions to Security Problems of Rivest and Shamir's PayWord Scheme

Norio ADACHI, Satoshi AOKI, Yuichi KOMANO, Kazuo OHTA

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The PayWord Scheme, invented by Rivest and Shamir, is an efficient micropayment scheme utilizing a hash function. We point out that the scheme has the following problem: a malicious customer can damage the bank by purchasing in excess of the customer's credit which the bank has guaranteed by issuing a certificate. Generally, there are two positions of the bank with regard to the certificate. Position 1: the bank takes full responsibility for the certificate and compensates all payments created by the customer's purchases; and Position 2: the bank does not redeem payments exceeding a limit set for the customer and shares the loss with the shop if trouble occurs. In the PayWord Scheme, the bank can reduce its risk by adopting Position 2 rather than Position 1. However, this paper points out that the bank can damage the shop in Position 2 by impersonating an imaginary customer and making the shop share the loss with the bank. We propose a micropayment scheme (countermeasure) that overcomes these problems.

Publication: IEICE TRANSACTIONS on Fundamentals Vol.E88-A No.1 pp.195-202

Publication Date: 2005/01/01

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DOI: 10.1093/ietfec/e88-a.1.195

Type of Manuscript: Special Section PAPER (Special Section on Cryptography and Information Security)

Category: Application

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Norio ADACHI, Satoshi AOKI, Yuichi KOMANO, Kazuo OHTA, "Solutions to Security Problems of Rivest and Shamir's PayWord Scheme" in IEICE TRANSACTIONS on Fundamentals, vol. E88-A, no. 1, pp. 195-202, January 2005, doi: 10.1093/ietfec/e88-a.1.195.
Abstract: The PayWord Scheme, invented by Rivest and Shamir, is an efficient micropayment scheme utilizing a hash function. We point out that the scheme has the following problem: a malicious customer can damage the bank by purchasing in excess of the customer's credit which the bank has guaranteed by issuing a certificate. Generally, there are two positions of the bank with regard to the certificate. Position 1: the bank takes full responsibility for the certificate and compensates all payments created by the customer's purchases; and Position 2: the bank does not redeem payments exceeding a limit set for the customer and shares the loss with the shop if trouble occurs. In the PayWord Scheme, the bank can reduce its risk by adopting Position 2 rather than Position 1. However, this paper points out that the bank can damage the shop in Position 2 by impersonating an imaginary customer and making the shop share the loss with the bank. We propose a micropayment scheme (countermeasure) that overcomes these problems.
URL: https://globals.ieice.org/en_transactions/fundamentals/10.1093/ietfec/e88-a.1.195/_p

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@ARTICLE{e88-a_1_195,
author={Norio ADACHI, Satoshi AOKI, Yuichi KOMANO, Kazuo OHTA, },
journal={IEICE TRANSACTIONS on Fundamentals},
title={Solutions to Security Problems of Rivest and Shamir's PayWord Scheme},
year={2005},
volume={E88-A},
number={1},
pages={195-202},
abstract={The PayWord Scheme, invented by Rivest and Shamir, is an efficient micropayment scheme utilizing a hash function. We point out that the scheme has the following problem: a malicious customer can damage the bank by purchasing in excess of the customer's credit which the bank has guaranteed by issuing a certificate. Generally, there are two positions of the bank with regard to the certificate. Position 1: the bank takes full responsibility for the certificate and compensates all payments created by the customer's purchases; and Position 2: the bank does not redeem payments exceeding a limit set for the customer and shares the loss with the shop if trouble occurs. In the PayWord Scheme, the bank can reduce its risk by adopting Position 2 rather than Position 1. However, this paper points out that the bank can damage the shop in Position 2 by impersonating an imaginary customer and making the shop share the loss with the bank. We propose a micropayment scheme (countermeasure) that overcomes these problems.},
keywords={},
doi={10.1093/ietfec/e88-a.1.195},
ISSN={},
month={January},}

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TY - JOUR
TI - Solutions to Security Problems of Rivest and Shamir's PayWord Scheme
T2 - IEICE TRANSACTIONS on Fundamentals
SP - 195
EP - 202
AU - Norio ADACHI
AU - Satoshi AOKI
AU - Yuichi KOMANO
AU - Kazuo OHTA
PY - 2005
DO - 10.1093/ietfec/e88-a.1.195
JO - IEICE TRANSACTIONS on Fundamentals
SN -
VL - E88-A
IS - 1
JA - IEICE TRANSACTIONS on Fundamentals
Y1 - January 2005
AB - The PayWord Scheme, invented by Rivest and Shamir, is an efficient micropayment scheme utilizing a hash function. We point out that the scheme has the following problem: a malicious customer can damage the bank by purchasing in excess of the customer's credit which the bank has guaranteed by issuing a certificate. Generally, there are two positions of the bank with regard to the certificate. Position 1: the bank takes full responsibility for the certificate and compensates all payments created by the customer's purchases; and Position 2: the bank does not redeem payments exceeding a limit set for the customer and shares the loss with the shop if trouble occurs. In the PayWord Scheme, the bank can reduce its risk by adopting Position 2 rather than Position 1. However, this paper points out that the bank can damage the shop in Position 2 by impersonating an imaginary customer and making the shop share the loss with the bank. We propose a micropayment scheme (countermeasure) that overcomes these problems.
ER -