Electrical computers and digital processing systems: support – Multiple computer communication using cryptography – Protection at a particular protocol layer
Reexamination Certificate
1996-11-13
2004-05-25
Smithers, Matthew (Department: 2137)
Electrical computers and digital processing systems: support
Multiple computer communication using cryptography
Protection at a particular protocol layer
C705S039000
Reexamination Certificate
active
06742125
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention is directed, in general, to cryptography and, more specifically, to a distributed protocol that allows transactions to be communicated securely by a small number of messages and a decentralized network in which the protocol may be employed for commerce thereover.
BACKGROUND OF THE INVENTION
The availability of more efficient, reliable and cost effective computers has allowed great numbers of small to medium sized companies, as well as individuals, to acquire tools necessary to compete in today's electronic marketplace. The immeasurable gains in technology experienced by the computer industry have allowed both companies and individuals to rely on commercially available computers, such as personal computers (“PCS”), to meet their information processing and communication needs. To that end, most PCS are equipped with an interface that may facilitate communication over private or public networks, such as the I
NTERNET.
Given the inherent insecurity of electronic commerce, particularly over public networks, it was long felt that a system that could ensure secure electronic transactions would be highly advantageous. In general, such a system would authenticate the parties to the transaction and provide transactions that are resistant to tampering—a secure system should be resistant to fraud.
One moderately successful effort introduced the concept of “closed” communities—local and long distance telephone companies, cable companies, cellular telephone companies, E-mail services and electronic service providers. These communities are “closed” because their customers have to enter into a contractual relationship with a provider before entering into the program, thus the customer must be a member in order to use the offered products and services.
One adaption of this method is described in U.S. Pat. No. 5,453,601 (the “'601 Patent”), entitled E
LECTRONIC
-M
ONETARY
S
YSTEM
, issued Sep. 26, 1995, which is incorporated herein by reference. The '601 Patent introduces an anonymous electronic monetary system as an alternative medium of exchange to credit cards, cash, checks, etc. More particularly, the system uses money modules encapsulated in tamper-proof envelopes to store and transfer electronic notes.
This system of remote, anonymous purchases, however, fails to ensure both payment and delivery. If a customer purchases a software package anonymously over the I
NTERNET
, for example, there is no mechanism to ensure that the customer will receive the software if the customer has already paid for the software. Conversely, how can the merchant be sure it will be paid if it delivers its goods before payment. Thus, to ensure payment and delivery, the customer and merchant are required to give up their anonymity, one of the primary objects of the system.
An alternate system uses a distributed, low-overhead, digital cash protocol. See, T
HE
M
ILLICENT
P
ROTOCOL FOR
E
LECTRONIC
C
OMMERCE
, by Mark S. Maasse, published at the F
IRST
USENIX W
ORKSHOP ON ELECTRONIC
C
OMMERCE
, New York, N.Y. (Nov. 12, 1995) (the “Millicent System”). The Millicent System introduces a digital scrip, which is digital “money,” that is honored by a single merchant. The obvious drawback being the requirement of preparation before a purchase from a new merchant, namely, purchasing scrip from a third-party broker—a separate transaction having its own overhead. An added complication involves a system for returning change as the value of the scrip is often higher than the price of the goods. Thus the merchant returns change to the user in the form of “other” scrip—which is honored only by the issuing merchant—forcing the customer to use the same with the merchant at a later time or to redeem it with the third-party broker, possibly for some processing fee.
These conventional systems and protocols, like others common to the industry, are expensive, whether overtly or surreptitiously. The widespread use of electronic commerce on the I
NTERNET
and, more particularly, the W
ORLD
W
IDE
W
EB
, requires mechanisms for dealing with high volumes of low-priced transactions—transactions of such low monetary value that merchants cannot afford to communicate with the bank for every transaction. There is a need therefore for a class of electronic commerce protocols that structures and secures electronic commercial transactions that can be optimized most preferably to be comparable to substantially free I
NTERNET
and W
ORLD
W
IDE
W
EB
browsing in terms of messaging overhead.
SUMMARY OF THE INVENTION
The present invention introduces the broad concept of securely communicating a financial transaction without requiring communication between a central authority and either a merchant or a customer during the transaction. This significantly reduces the bandwidth required to complete the transaction, as only three messages (the quotation, order and a reply thereto) are required to complete the transaction. The quotation may be sent in response to an optional quotation request sent from the customer to the merchant.
Thus, to address the above-discussed deficiencies of the prior art, the present invention provides a protocol and system for securely communicating a financial transaction between a customer and a merchant and a distributed computer network employing the protocol or system. An exemplary central authority may be associated with a central authority private key K
s
ca
and a central authority public key K
p
ca
, and is responsible for assigning a customer account (“C
ACCT
”) to the customer and a merchant account (“M
ACCT
”) to the merchant. The customer is associated with a customer private key K
s
c
and a customer public key K
p
c
; the merchant is associated with a merchant private key K
s
m
and a merchant public key K
p
m
. Of course, the central authority may be separate entities, one associated with the customer and the other with the merchant.
The protocol includes the steps of: (1) sending a quotation from the merchant to the customer, the quotation including at least the K
p
m
, a K
s
ca
-signed signature that is a function of the M
ACCT
, an unsigned copy of a price and a K
s
m
-signed signature that is a function of the M
ACCT
and the price, (2) replying to the quotation by sending an order from the customer to the merchant, the order including at least the K
p
c
, a K
s
ca
-signed signature that is a function of the C
ACCT
, an unsigned copy of the price and a K
s
c
-signed signature that is a function of the C
ACCT
, the M
ACCT
and the price and (3) replying to the order by the merchant filling the order. The invention employs signatures based on public key cryptography (e.g., RSA, etc.).
For security purposes, each of the central authority, the customer and the merchant may, be responsible for selecting their respective public and private keys. The central authority may also be responsible for generating a merchant identification, “Mid,” for the merchant which may contain the merchant's account, M
ACCT
, and the merchant's public key, K
p
m
. The central authority may generate a signed merchant identification, “SMid,” that contains Mid and a K
s
ca
-signed signature that is a function of Mid. The central authority may generate a customer identification, “Cid,” for the customer, that contains the customer account, C
ACCT
, and the customer's public key K
p
c
. The central authority may generate a signed customer identification, “SCid,” that contains Cid and a K
s
ca
-signed signature that is a function of Cid.
Most preferably, once the customer sends the order and the merchant accepts it (either with or without verification thereof), neither the customer nor the merchant is authorized to repudiate the transaction. It is preferred that only the central authority or an arbiter (to be defined below) be given that authority. Further, public-key encryption allows each party to authenticate the other and any information obtained from the other (such as price) without compromising encryption keys.
It should be noted that, since th
Gabber Eran
Silberschatz Abraham
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