Method for authenticating objects identified by images or other identifying information

The method and system of the present invention utilizes public-key cryptography to create "secure" titles for personal and real property such as vehicles and the like. The title preferably comprises a card in which is stored a digital signature of one or more identifiers such as a vehicle identification number, the vehicle license plate and the owner's name. To effect a transfer of the property, the digital signature on the title must first be shown to have been generated from the one or more identifiers.

TECHNICAL FIELD 
The present invention relates generally to techniques for preventing 
counterfeiting or otherwise illegal use of documents (e.g., titles, 
licenses, proofs of insurance, etc.), especially documents relating to 
personal property such as vehicle. 
BACKGROUND OF THE INVENTION 
Vehicle theft is a major crime problem, especially in urban areas. One 
contributing factor to this problem is the ease with which stolen vehicles 
or their parts can be recycled in the marketplace. As is well known, 
manufacturers place or engrave a so-called vehicle identification number 
(VIN), which is unique to the particular vehicle, on the engine and all 
major parts to facilitate identification. The VIN is sometimes identified 
on the vehicle title, which is normally a conventional paper document 
issued by the particular governmental authority having the appropriate 
jurisdiction over the vehicle. The other standard vehicle identifier is 
the vehicle's license plates. Currently, titles, VIN's and license plates 
are quite unrelated to each other, thereby contributing to the ease with 
which an unauthorized party can recycle a stolen car. 
There has therefore been a long-felt need to overcome these and other 
problems associated with securing documentation associated with personal 
or real property. 
BRIEF SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a method and system for 
creating secure "titles" for personal and real property. 
It is a further object of the present invention to describe a method 
enabling a given authority to secure valuable documents (such as titles, 
licenses, passports, registrations, etc.) from alteration and fraudulent 
use. 
It is a further object of the invention to provide enhanced techniques to 
prevent legal titles or other documentation from being counterfeited or 
otherwise illegally altered. 
It is a still further object to use public-key cryptography methods and 
systems to secure title documentation of any personal or real property 
wherein such property is identifiable by a unique identifier. 
Yet another object of the invention is to provide for digitally-secure 
physical or virtual titles to thus facilitate the transfer of personal or 
real property. 
In the preferred embodiment, a title according to the present invention 
include an identifier uniquely associated with the personal or real 
property to be identified (e.g., a vehicle identification number), and 
information directly or indirectly identifying the legal owner of the 
property. The identifier and the information are preferably concatenated 
into a data string which is then digitally signed using a secret key of a 
public-key cryptosystem pair. To verify the title, a transaction terminal 
uses a corresponding public key to decrypt the data string. 
The method and system of the present invention thus utilizes public-key 
cryptography to create "secure" titles for personal and real property such 
as vehicles and the like. The title preferably comprises a card in which 
is stored a digital signature of one or more identifiers such as a vehicle 
identification number, the vehicle license plate and the owner's name. To 
effect a transfer of the property, the digital signature on the title must 
first be shown to have been generated from the one or more identifiers. 
The foregoing has outlined some of the more pertinent objects of the 
present invention. These objects should be construed to be merely 
illustrative of some of the more prominent features and applications of 
the invention. Many other beneficial results can be attained by applying 
the disclosed invention in a different manner or modifying the invention 
as will be described. Accordingly, other objects and a fuller 
understanding of the invention may be had by referring to the following 
Detailed Description of the preferred embodiment.

DETAILED DESCRIPTION 
The techniques described below are useful to provide titles or other 
documentation that are "secure," i.e., titles that cannot be counterfeited 
or illegally changed in any feasible way. Although the technology is 
described in the context of securing vehicle titles, the present invention 
is not intended to be limited to such particular application. It should 
readily be appreciated by those of skill in the art that the present 
invention has direct applicability to secure any and all kinds of titles 
and documentation (e.g., registrations, licenses, proof of insurance or 
inspection, proof of identity, etc.) and the invention should be and is 
intended to cover any and all such types of documentations, whatever their 
particular purpose or association may be. Thus, for example, the invention 
is useful to secure titles of all types of property including, without 
limitation, precious or semiprecious gems or stones, paintings, antiques, 
artifacts, art objects, firearms or guns, or any other object whose 
particular authenticity needs to be verifiable for whatever purpose the 
owner or transferor desires. Of course, the techniques are also useful in 
connection with real property such as deeds, surveys, and the like. 
According to the present invention, so-called "digital signatures" are used 
to bind in an untamperable way certain quantities associated with a piece 
of personal or real property to thereby realize a "secure title" for the 
property. Digital signatures provide high security for the system at 
generally low cost. In the preferred embodiment of the invention, a 
digital signature is derived from a data stream (which will be described 
below) using a private or secret key of a "public-key cryptosystem" key 
pair. A "public-key cryptosystem" is a well-known security scheme which 
includes two "keys," one key which is public (or at least the key pair 
owner does not really care if it becomes public) and one key which is 
private or non-public. All such public-key cryptosystem pairs include a 
common feature--the private key cannot be determined from the public key. 
One such scheme is described mathematically in U.S. Pat. No. 4,995,081, 
which is hereby incorporated by reference. 
By way of further background and with reference to FIG. 1, a "title" card 
10 is provided for maintaining the digital signature as well as perhaps 
other identifying information as will be described. The card is 
conventional in the physical sense that it includes a body portion 12 and 
a memory 16. A display 14 may also be provided. Although not meant to be 
limited, the memory 16 is preferably a magnetic strip or similar media, or 
an electronic memory such as a PROM, affixed to or embedded in the card in 
a known manner. The card 10 may or may not include a programmable 
microprocessor embedded in the body portion. Some portion of the memory 
may be "protected" against access such as described in the prior art. Such 
"protected memory" or similar data carrier products are available in the 
marketplace from such manufacturers as Innovatron. The card 10 may 
alternatively be any type of smart, magnetic, laser or other type of data 
carrier. 
With reference to FIG. 2, in the preferred embodiment, an issuing terminal 
76 includes a microcomputer 80 and associated memory devices 82 for 
storing operating programs and application programs for carrying out the 
invention. Input/output devices, such as a keyboard 84 and display 86, are 
provided for interfacing the terminal to the card issuer. One or more 
transaction or "verification" terminals 78 may also be provided for the 
purposes to be described. Such terminals preferably include a 
microprocessor 88, associated memory 90 and appropriate input/output 
devices such as a cardreader 92, keyboard 94 and display 96. 
Now assume that it is desired to secure a vehicle title and that such 
security is desired by an Insurance Company. According to the invention, 
the Insurance Company or other suitable authority is provided with an 
issuing terminal to produce a digital signature of a bit stream on a card 
10. That is, the Insurance Company has a public (verification) key and a 
matching private (signing) key, and the public and private keys form a key 
set of a public-key cryptosystem. To digitally sign a bit stream X, the 
Insurance Company (using its secret key) computes a second bit stream X' 
and writes it along with X on a card. X' mathematically vouches that the 
Insurance Company has "approved" the string X because: 
1. everyone, given X and the Insurance Company's public key, can verify 
(e.g., using a transaction terminal) that X' is the Insurance Company's 
digital signature of X, and 
2. no one, without the right key, can forge the Insurance Company's digital 
signature, Y', of a new string Y. 
The use of public-key cryptography for this application is particularly 
advantageous because different bit streams have different digital 
signatures and because changing a single bit in an already signed bit 
stream causes the new, corresponding signature to change in a dramatic and 
unpredictable way. Thus a digital signature can be thought of as a very 
special sequence of "control bits." 
According to the invention, the title of a car whose VIN number is X, will 
preferably comprise a card 10 containing the Insurance Company's digital 
signature, X', of X (and possibly also X itself). This card can be 
inserted in a transaction terminal, which reads the information written on 
the card and checks that X' is the Insurance Company's digital signature 
of X. (Indeed, all such units will possess the Insurance Company's public 
verification key.) No one can, however, make a fake title for a stolen 
car, since the thief will not know the Insurance Company's secret signing 
key. 
The above technique is enhanced by incorporating the vehicle's license 
plate number. For instance, if a car has a VIN number V and a license 
plate number L, let X be the number obtained by combining V and L (e.g., 
by concatenating V and L). Then the title will comprise a card containing 
the number X', the Insurance Company's digital signature of X. This it 
will be impossible for an imposter to replace the license plate of a 
stolen car, since for any new number L', X' will not be the Insurance 
Company signature of XL'. The technique of course also allows for 
"personalized" license plates in lieu of or in addition to the plate 
number L. 
In this manner the license plate number or other identifier is securely 
tied in the title. It should be appreciated that once a secure title of 
this form has been verified to be authentic, even if it was stolen with 
the car, it allows someone, e.g., a policeman or other government 
authority, to quickly verify that a car has been stolen by verifying 
whether a given license number has reported to stolen. This solves the 
common problem where, by taking away the license plate of a car not 
reported stolen (or not stolen or all) and mounting it on a stolen car, a 
thief may have a stolen car appear legitimate. 
The system is yet further enhanced by incorporating the name of the car's 
owner. For instance, if a car has a VIN number V and a license plate 
number L, and its owner's name is N, then the title preferably comprises a 
card containing the number X', the Insurance Company's digital signature 
of the number X obtained by concatenating V, L, and N (and possibly some 
of V, L, and N themselves). This embodiment has many advantages. For 
instance, the owner can prove ownership of the car by providing the new 
title and a personal ID showing that his/her name is N. By securely 
including the name of the owner, an important advantage is provided 
because when the car is legitimately sold the owner must be present. 
Besides the owner's name, the Insurance Company may include in the title 
other information about the owner; e.g., the names of other authorized 
drivers. 
More generally, besides V (or L, or N), the new title can contain an 
arbitrary information string, I. This string is digitally signed by the 
Insurance Company together with V (and/or L and N); that is, the new title 
will contain the Insurance Company's digital signature of the string VI. 
As described, string I may consist of L or N, or both, but may also be, 
for example, a description of the car or even a digitized image of the 
car. This may be useful, in case of accidents, to establish how the car 
"looked like" before and after an accident or other repair. The 
information string may include other important information about the 
vehicle such as an odometer reading or times and dates of service visits. 
Several variations of the above techniques are also envisioned by the 
present invention. For instance, rather than the name of the owner, N, the 
new title may incorporate a string f(P), where P is a password known to 
the owner (and preferably only to the owner), and "f" is a one-way 
function. One-way functions are functions that are easy (for everyone) to 
compute but hard (for everyone) to invert. That is, if "f" if such a 
function, every one can, given, say, a number A, if it is long enough. 
Indeed, a brute-force search for A would require astronomical time even 
with the most modern and sophisticated computers if A consists of 100 
digits or of a long enough sentence.) 
Now assume that a new car has a VIN number V and license plate number L. 
According to the invention, the first legitimate owner of the car chooses 
a suitable large alphanumeric string A (e.g., his/her mother's maiden 
name) and sets f(A)=B. Then the number X is obtained by concatenating V, L 
and B, and the title will contain the Insurance Company's digital 
signature, X', of X. In this manner, only the legitimate owner can prove 
that he/she owns the car, since only he/she knows A. To verify ownership, 
one may in fact check that X' is the Insurance Company's digital signature 
of X=VLB, and then ask the alleged owner for the value A, and verify that 
indeed f(A)=B. 
One advantage of this scheme is that the entire ownership history of a car 
can be certified without revealing the names of the owners. For instance, 
the first entry on the title contains the Insurance Company's digital 
signature of X=VLB as above. When the first owner wants to sell the car, 
he/she will reveal to the Insurance Company the value of A (such that 
f(A)=B), while the new owner will chose a value C such that f(C)=D. Then a 
second entry is added to the title containing the (possibly new) Insurance 
Company's digital signature of the concatenation of V, L (or possibly a 
new L', as when the second owner wants a personalized license plate), A 
and D. That is, the second entry certifies that the car has been 
legitimately sold once. In fact, anyone can read A from the second entry 
and verify that f(A)=B, the value unalterably bound to V in the first 
entry. This means that the first legitimate owner has consented to the 
sale, since he/she has willingly revealed the correct and unpredictable 
value A. The second entry may actually replace the first one (or the old 
title is destroyed and a new one is issued only containing the second 
entry). Successive sales are handled in a similar manner. The new buyer is 
thus always informed of the number of previous owners. It is thus possible 
to count the number of values B, D, etc. that are added to the title at 
each sale. Such a title can be conveniently left in the automobile, since 
stealing it will not enable a thief to sell the vehicle in a legitimate 
way; he will not be able to reconstruct the value A from B (if the car had 
only one owner when stolen), or the value C from D (if the car had two 
owners), etc. 
An alternative method for obtaining similar benefits may be used if the 
digital signature adopted is such that a signature X' for a string X does 
not betray X, that is, if X cannot be reconstructed from X'. In this case, 
the new title may consist of, say VI (where I is the information string) 
and the Insurance Company digital signature, X', of VIA (where A is a 
string known to the owner). Thus, if the owner willingly provides A, 
anyone can verify that X' is the Insurance Company's digital signature of 
VIA, thereby verifying that both V and I have been certified, while 
without the cooperation of owner X' is quite useless. 
As for another variant, if the title comprises a smart card, rather than 
sending or otherwise exhibiting or making available to the transaction 
terminal the digital signature of the relevant information, the card may 
simply "convince" such apparatus that it contains (e.g., in a protected 
area of the chip) the relevant signature, without explicitly giving it. 
One such technique for establishing such proof of legitimacy is described 
in U.S. Pat. No. 4,995,081, which as noted above is incorporated herein by 
reference. 
Alternatively, rather than using a digital signature that can be 
universally verified (e.g., by means of a public verification key), the 
title may contain a private digital signature, that is a string that can 
be verified by a selected group of people (e.g., those who know, or whose 
verifying apparati know, a given secret key). This is a so-called 
private-key cryptosystem. 
According to another embodiment of the invention, it is not required that 
the titles be specific physical objects (e.g., a magnetic, laser, or smart 
card). The advantages of the present invention can also be realized in a 
virtual manner, for instance, by means of an accessible database. As in 
the previous examples, the database preferably contains VINs digitally 
signed by a proper authority (and possibly by different authorities, each 
having a different signing scheme and different key, both public and 
secret). To verify the legitimacy of a title, an inquiring party (e.g., an 
insurance agent, policemen, a bank officer wishing to verify the 
information concerning collateral, departments of motor vehicles, etc.) 
can query the database with, say, a given VIN V, and receive in return a 
pair (V,S), where S is the digital signature of v by a specified 
authority. The querying party can then verify that S is a correct digital 
signature of V for the specified authority, whose verification key is 
publicly known. Thus, while the database can be made widely queriable, 
preferably only the proper authority can insert data therein. In fact, 
even assuming that a malicious party were able to illegally insert a given 
VIN V into the database, he would not be able to forge the digital 
signature of V (by the proper authority) that should be stored together 
with V and should be retrieved in case of a query. Without this signature, 
inserting V into the database is essentially useless, since V alone will 
not be accepted or believed by the querying parties. This security aspect 
is particularly attractive in that it protects a large and distributed 
database so as to make sure that no one can illegally write his own data 
in such database. 
While described in the context of a vehicle title, it should be appreciated 
that the method extends to all other kinds of titles, when the object(s) 
of interest possess a string that, like the VIN, acts as a unique 
identifier of the object. Sometimes this unique identifier can be 
constructed ad hoc. For instance, in the case of a land title the string 
in question can be obtaining by writing down a sufficiently detailed 
English description of a given lot. This English string can then be 
digitized if desired. 
It should be appreciated by those skilled in the art that the specific 
embodiments disclosed above may be readily utilized as a basis for 
modifying or designed other structures for carrying out the same purposes 
of the present invention. It should also be realized by those skilled in 
the art that such equivalent constructions do not depart from the spirit 
and scope of the invention as set forth in the appended claims.