II. What PKI Does - The Killer Apps
F. Non-Repudiation
Non-Repudiation blocks the sender's false denial that
the sender sent a particular message. Whereas authentication of identity
may be sufficient for applications where the sender needs only to convince
the recipient of her identity, the legal requirements of many e-commerce
applications require non-repudiation sufficiently robust for the recipient
to prove to a third party such as a judge or jury that the sender's denial
was false. Conventional crypto with a single shared secret PIN may
be sufficient for two-party authentication, but PKI technology is needed
for three-party nonrepudiation on open systems such as the Internet.
May 24, 1999
- Powerpoint slides (Needs Microsoft
Internet Explorer Browser) of Charles
Merrill of McCarter & English
LLP, "Security Issues in Online Trading," in New York City May 24,
1999, sponsored by Institute of International Research. Presentation
analyzes illustration of online day trader attempting to repudiate improvident
trade under (i) weakness of existing security paradigm using SSL and single
key PIN, and (ii) future PKI designed to provide strong non-repudiation
for online transactions.
April 28,
1999 - "Teen bids away $3.2 million of parents' money - S. Jersey boy finds
eBay account password." The Newark NJ Star-Ledger reported
(relaying a report in the Ontario National Post) that a 13-year
old boy used his parents' auction account (presumably with a single-key
PIN or passphrase) with eBay to successfully bid on a $1.2 million medical
center in Jacksonville, Fla, a Van Gogh sketch, a 1971 Corvette convertible,
and a $400,000 bedroom suite that once belonged to Sir John A. Macdonald,
Canada's first prime minister. When the problem was discovered, the
account was suspended, and the bids subsequently canceled.
The article didn't state whether the sellers of these
items were able to close sales at or near the bidding level of the bidders.
If not, the repudiated bid caused the innocent sellers some serious damage.
The really interesting additional question is whether the parents were
telling the truth when they claimed that the bid made with their password
was unauthorized. If authentication of eBay bidders were by PKI instead
of a PIN, what would be the result of a suit by the damaged sellers against
the parents? What additional facts would you want to know?