Hardware cartridge representing verifiable, use-once authorization

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DESCRIPTION

1. Technical Field

The invention relates to a secure, electronic device capable of use as a use-once authorization mechanism or token.

2. Background Art

In many fields there are occasions on which there is need for a device which can be used as evidence of the bearer's authority, identity or entitlement to some right or privilege, where this evidence is applicable to one and only one use, relatively inexpensive to manufacture, simple to verify or authenticate and difficult to forge or simulate. While such a device has some of the properties associated with a mechanical key (when used with a mechanical lock), there are vast differences; a key is relatively easy to copy and it is distinctly not a use-once device. Actually, the device in accordance with the invention may be likened to a wax seal used on an envelope to evidence the fact that the contents of the envelope had not been accessible between the time the seal was put in place and the time the seal was broken. In order to improve the qualities of wax seals, users imprinted them with a distinctive pattern so that it would be more difficult to copy or simulate the wax seal than had the pattern been omitted.

Uses of such a verifiable, use-once device or token arise in a variety of fields. For example, copending application Ser. No. 927,629, filed Nov. 5, 1986, now U.S. Pat. No. 4,817,140, issued Mar. 28, 1989, the disclosure of which is incorporated herein by this reference, assigned to the assignee of this application, describes a software protection system using a single key crypto system, a secure coprocessor and a hardware based authorization system to inhibit copying of protected software. In this mechanism the token is provided in the form of a hardware cartridge which represents authorization to the coprocessor to accept the right to execute the software. When the hardware cartridge is presented to a cooperating coprocessor, the authenticity of the cartridge is challenged, and if verified, the right to execute an associated application or piece of software is accepted by the cooperating coprocessor, leaving the cartridge in such a condition that it cannot thereafter authorize other cooperating coprocessors.

In another application, the hardware cartridge could represent the right of the bearer to passage on some transportation system, as would an airline ticket. The right represented by an airline ticket may have significant value, but the carrier issuing the "ticket" finds it necessary to receive assurance that the "ticket" is used only once. As will be described below, the hardware cartridge described herein as the properties allowing it to be used as such a "ticket".

Finally, in another context, the hardware cartridge can represent the right of entry to some secure location. In this case, the use-once feature assures the entity granting the right of entry that the cartridge can only grant access to a single bearer so that even if the bearer passes the cartridge to another individual at the time access is granted, the cartridge cannot be thereafter again used to authorize access to another individual. In the event the bearer leaves the secure premises and is entitled to subsequent access, he is provided with a different hardware cartridge, or the original hardware cartridge is recharged, hence re-enabled.

As has been indicated, in order to be reliable the hardware cartridge should be difficult, and preferably arbitrarily difficult, to simulate. In a similar setting, Halpern in U.S. Pat. No. 3,906,460, suggests that a secret "check" character be employed and the cartridge arranged so that it rejects information in the absence of the correct "check" character. In the applications described by Halpern, where the token is employed on the premises of the party issuing the token (for example, such as the Bay Area Rapid Transit System, or a bank), this may be a useful technique. On the other hand, in many applications (such as the software protection application described in copending application Ser. No. 927,629, now U.S. Pat. No. 4,817,140, or in gaining access to a secure space) a person bent on mischief or crime may have not only access to the token or cartridge itself, but also to the transaction by which a token is validated. Under these circumstances, the Halpern technique of using a secret "check" character would immediately fail since by once observing a valid transaction such person could thereafter simulate or copy the secret "check" character. Thus it must be recognized that not only will the hardware cartridge be accessible to a determined pirate, but the transaction by which the cartridge is validated (including all the information which flows between the cartridge and any validating device) may also be accessible to the pirate. Thus, the cartridge should be arranged so that the information exchanged during a validating transaction, while sufficient to verify the authenticity of the cartridge, is inadequate to simulate the cartridge at any later time.

SUMMARY OF THE INVENTION

The invention meets these and other objects by providing a hardware cartridge which is capable of storing information (token data) which can be used to authenticate the source of the physical cartridge as well as the fact that it has not heretofore been employed. In accordance with the invention, the hardware cartridge is arranged so that this protection is maintained notwithstanding the fact that a pirate may have access not only to the hardware cartridge itself but to a transaction in which a specimen cartridge is validated by some validating mechanism.

In accordance with the invention, the token data is stored electronically; the apparatus in which it is stored is provided with physical security. Two suitable techniques for physical security include:

1) the techniques described in applicant's copending application Ser. No. 927,309, filed Nov. 5, 1986, the disclosure of which is incorporated herein by this reference, and

2) implementing the electronic storage along with peripheral hardware on a single chip.

In one embodiment of the invention the token data is stored in a device containing memory elements in the form of shift registers. As will be described, the token data is divided into at least two, mutually exclusive portions. More than two portions may also be employed. The token data can be in the form of a secret "number", typically represented in the storage device in binary form.

The validating apparatus has access to each and every valid "number". The means for providing this access will be described below. The hardware cartridge includes a connector so that it can be electrically connected to the validating device. If the validating device merely stimulated the hardware cartridge to generate an electronic representation of the "secret" number, the pirate having access to the transaction could simulate the effect of the cartridge to the detriment of the security system.

Accordingly, in accordance with an embodiment of the invention, the validation transaction does not expose all of the secret "number"; rather, a sufficient portion of the secret "number" is exposed, which portion is sufficient to verify the presence of the secret "number" stored in the hardware cartridge but simultaneously inadequate to allow a person bent on mischief or crime to simulate the effect of the hardware cartridge.

The validating transaction takes the form of a challenge implemented by a query. The validating apparatus may generate the query as a random number; in the event the token data is divided into two portions, the random number can be represented in binary notation. For each bit of the query, one bit from one of the two halves of the token data is output to the validating mechanism; which bit is selected is determined by both the position and value of the corresponding bit in the "query". At the conclusion of the transaction, exactly 50% of the token data has been exposed; which 50%, however, is determined by the "random" number. While it is assumed that the pirate will have access to both the random number and the response, that information is useful only to the extent that he can somehow force the validating mechanism to again generate the identical random number in the course of a subsequent challenge.

In accordance with this embodiment of the invention, the shift register storing the token data has special properties to ensure that at the completion of the query/response transaction, the hardware cartridge which initially stored the token data thereafter no longer stores the token data. This ensures that a hardware cartridge, once used, cannot be used again, unless it is recharged by the validating mechanism. Clearly, it is critical that this recharging not be performed in such a manner or location that it can be observed by a person bent on mischief or crime.

In accordance with the embodiment of the invention being described, the hardware cartridge includes two shift registers, each storing mutually exclusive halves of the token data. The shift out terminals of the two shift registers are coupled to the inputs of a 2/1 multiplexer. The output of the 2/1 multiplexer is stored in a D type latch, the output of which is the output of the hardware cartridge, e.g. the response terminal. The validating mechanism is coupled to a connector or, the hardware cartridge which includes, in addition to an output terminal, a select terminal, a clock terminal and power and ground terminals. The clock terminal is used to couple clock pulses to step the shift registers and clock the latch. The select terminal is coupled to the control terminal of the 2/1 multiplexer. The validating mechanism's query and clock pulses are input to the token terminals. The 2/1 multiplexer selects at each clock time the output of one or the other of the shift registers. The selected contents of the shift registers are latched depending on the particular select pulse pattern into the D-latch and are output from there to the validating mechanism. The shift registers have input terminals which are connected to data input terminals in the connector. The connector's data input terminals may or may not be connected to terminals in the validating mechanism. Regardless of the connection of these data input terminals, after a number of clock pulses had been received which is equal in