FIELD OF THE INVENTION

The present invention relates generally to confirming the authenticity of an object, more particularly, to a certificate with an extension field for use in the confirmation of the authenticity of an object for a subset of devices.

BACKGROUND OF THE INVENTION

Enhanced security is becoming increasingly relevant regarding the operation of many devices, especially where external influences can sometimes promote less than altruistic intentions. In an effort to minimize the opportunities for external influences to have harmful effects relative to the operation of the device, digital certificates have been used in connection with verifying and/or authenticating the trustworthiness of an object, such as a program or data, and/or, more directly, the originator of the object.

A secure system generally involves trusted programs or data structures, such as operating systems, file managers, application programs or data files. In some instances, the trustworthiness of the system can be enhanced by hardware and software elements, which resist tampering. In many instances, the trustworthiness of such a system involves multiple certificates corresponding, respectively, to the originator of most if not all of the signed elements forming such a system. Each certificate is often issued in connection with a certificate authority, which generates and manages the certificate creation process, and helps to insure the validity of the certificates. For each originator of a signed element for which a certificate is desired, a certificate signing request will be forwarded to the certificate authority. The certificate authority will then generally respond, in appropriate instances, with a signed certificate. A signed certificate is commonly generated using a secret private key, which in conjunction with a corresponding generally available public key, can be validated by the target device or recipient.

The signed certificate in turn, authorizes a third party to generate signed content, subject to the limitations outlined in the signed certificate. However, in instances where an originator does not have a signed certificate, a signature for the content must alternatively be requested from a certificate authority. Because the signature associated with the content is dependent upon the specific contents, a unique signature must be

separately generated for each unique form of content.

This can provide problems for developers of content, which require the certificate authority to sign their content, such as developers of application programs, which may have security mechanisms in place, who want to frequently build and test their efforts. Frequent builds correspondingly would presumably require frequent content signing requests, associated with each new version of the content. However having a certificate authority fulfill frequent signature requests may not always be feasible, and in some instances the ability to receive signed certificates may not always be timely. One way to avoid some of these concerns associated with testing programs, including the testing of any associated security mechanisms themselves, may be for the third party developer to obtain an appropriate certificate, which would enable the third party developer to sign their own content.

However at least one of the concerns associated with the potential unrestricted signing of content includes instances where a program, which may not be ready to be released and/or may not be stable (i.e. may contain security holes or contain harmful errors), may be allowed to propagate beyond the systems that are being used to test the program. In such an instance, a valid certificate which allows for a relatively unrestricted signing of a program may make the detection of a program with stability issues more difficult to detect, and/or may help to circumvent some security controls, which might otherwise limit the undesirable propagation of the content.

Still further the ability of a third party to be able to sign content for unrestricted use would compromise the trust of the system. The certificate authority would no longer be able to insure the integrity of all of the content being signed, thereby potentially marginalizing any benefit associated with requiring that the content be signed. As a result, the degree to which the signed content can be trusted could similarly be compromised. Generally, for trust to be effective, it needs to be reasonably certain.

Consequently, a certificate and a method for producing and/or verifying a certificate, which can be used to authorize trusted access to a restricted number of devices, for example devices involved in the development and testing of an object, such as a program, would be beneficial.

SUMMARY OF THE INVENTION The present invention provides a certificate for use in confirming the

authenticity of an object for a subset of devices, where each device has a unique identifier. The certificate has a signature, and an authorized device list extension field, where the authorized device list extension field includes a list of one or more identification entries, which match the unique identifiers of the one or more devices for which the certificate is valid.

In at least one embodiment, the extension field additionally includes an enabled critical flag parameter.

The present invention further provides a device has a storage element including a unique identifier, and a processor adapted for receiving signed content. The processor includes a reception module, which is adapted for receiving the signed content including an associated certificate having a signature and an authorized device list verification extension field including a list of one or more identification entries, which match the unique identifiers of the one or more devices for which the certificate is valid. The processor further includes a validation module which is adapted for parsing the certificate for determining the validity of the certificate, wherein the validation module is adapted for validating the signature of the content, if upon parsing the certificate a match for the unique identifier is contained within a list of the one or more identification entries associated with the authorized device list extension field.

The present invention still further provides a method for producing a certificate associated with an object, which is authorized for a predefined list of one or more devices. The method includes identifying a list of one or more devices for which the certificate is authorized, each device having a unique identifier. An authorized device list extension field is then encoded, which includes a list of one or more identification entries, which comprises a match for each of the unique identifiers associated with the one or more identified devices. The authorized device list extension field is then associated with the corresponding object.

Further yet, the present invention provides a method for confirming the authenticity of an object for a subset of devices, the object having an associated certificate including a signature and an authorized device list extension field with a list of one or more identification entries. Each device has a unique identifier. The method includes parsing the certificate including comparing the unique identifier for the device with the one or more identification entries in the authorized device list extension field.

The authenticity of the object is then confirmed, if a match exists between the unique identifier for the device and at least one of the identification entries. The authenticity of the object is denied, if a match does not exist between the unique identifier for the device and at least one of the identification entries. These and other features, and advantages of this invention are evident from the following description of one or more preferred embodiments of this invention, with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an exemplary environment within which, in accordance with at least one embodiment, the present invention is adapted to operate;

FIG. 2 is a block diagram of a device adapted for receiving signed content and confirming the authenticity of the content, in accordance with at least one embodiment of the present invention;

FIG. 3 is a block diagram of a certificate including an authorized device list extension field, in accordance with at least one embodiment of the present invention;

FIG. 4 is a flow diagram of a method for producing a certificate associated with an object, which is authorized for a predefined list of one or more devices, in accordance with at least one embodiment of the present invention;

FIG. 5 is a flow diagram of a method for confirming the authenticity of an object for a subset of devices, in accordance with at least one embodiment of the present invention; and

FIG. 6 is a more detailed flow diagram of a method for confirming the authenticity of the object, for use in connection with at least some embodiments illustrated in FIG. 5. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

While the present invention is susceptible of embodiment in various forms, there is shown in the drawings and will hereinafter be described presently preferred embodiments with the understanding that the present disclosure is to be considered an exemplification of the invention and is not intended to limit the invention to the specific embodiments illustrated.

FIG. 1 illustrates a block diagram of an exemplary environment 10 within which, in accordance with at least one embodiment, the present invention is adapted to

operate. The environment generally includes a certificate authority 12, which is adapted for creating and managing one or more certificates. The certificates are typically associated with objects, and the corresponding sources of the respective signatures of the objects, that can be received by a device 14 where the trust level of the object is of interest. The device 14 will generally include computational and/or presentation capabilities, which are adapted for acting upon received objects. The device additionally includes a unique identifier 22, such as a unique identification value. In at least some embodiments, the unique identifier will be stored within a storage element, which is tamper-resistant and/or relatively tamper-proof. At least a couple of examples of various forms of exemplary devices 14 include personal computers, cellular telephones, radio telephones, selective call receivers, file servers, pagers, cordless telephones, audio players, set top boxes and personal digital assistants. However one skilled in the art will appreciate that the present invention could also be used with many other types of devices, without departing from the teachings of the present invention, including devices, which are interested in receiving trusted objects, such as a program or conveyable content.

The certificate authority 12 is coupled to and/or is integrated as part of a network 16. Such a network 16 may include any type of network that is capable of sending and receiving communication signals. In at least one embodiment, the network 16 can include a wireless communication network. The network 16 may additionally or alternatively include or be in communication with a data network, such as the Internet, an Intranet, a local area network (LAN), a wide area network (WAN), a cable network, and other like communication systems. The network 16 may also include or be in communication with a telecommunication network, such as a local telephone network, long distance telephone network, cellular telephone network, satellite communication network, cable television network and other like communication systems. Furthermore, the network 16 may include or be in communication with more than one network and may include a plurality of different types of networks. Thus, the network 16 may include or be in communication with a plurality of data networks, a plurality of telecommunication networks, or a combination of data and telecommunication networks and other like communication systems.

By being coupled to the network 16, the certificate authority can communicate

with other various elements, which are similarly coupled to and/or form part of the network 16, at least one such element including the device 14.

FIG. 1 additionally illustrates a certificate requester 18, which in many instances will be associated with the creator of the object, such as a program. In some instances the certificate requester 18 will be the creator of the object. When a certificate is desired relative to an object, which is to be used to confirm the authenticity of the object and/or the source of the object, a certificate signing request is forwarded to the certificate authority 12. The certificate authority 12 then creates a certificate to be used by the certificate requester 18 in connection with the signing of the content. In at least some embodiments, the certificate includes a signature, which is formed using the private key 20 of a public private key pair associated with the certificate authority. The public key and the signature are then conveyed to any device 14 desiring to receive and authenticate the object and/or the source of the object.

In many instances, the object and corresponding certificate will be conveyed to the device 14, via the network 16. However in some instances, the object may be able to be received directly from another device, such as a file server, which in some embodiments may be the certificate requester 18, and/or may be associated with the certificate requester 18. In some instances, the object may be conveyed via a physically transportable storage medium, such as a diskette, memory card, or compact disc, or other transportable form of storage.

FIG. 2 illustrates a block diagram of a device 14 adapted for receiving signed content and confirming the authenticity of the content, in accordance with at least one embodiment of the present invention. The device 14 generally includes a storage element 30 and a processor 32. The storage element 30 is adapted for storing a unique identifier 22, which is uniquely associated with the device 14.

The storage element can include both volatile and non-volatile forms of memory, many types of which are well known. One such example includes a semiconductor memory, such as a read only memory. Other examples include a fixed drive or hard drive, which commonly stores information magnetically. However any form of data storage may be suitable, as long as it supports the ability to at least initially store, and later retrieve the information contained therein. However for purposes of storing the unique identifier 22, the unique identifier will generally be stored in a non-

volatile portion of the storage element 30. In some instances the unique identifier 22 may be laser inscribed, and may be formed of one or more selectively blown fuses, and/or cut traces, which can be formed during the fabrication of a corresponding integrated circuit element. Correspondingly, the ability to modify an existing unique identifier 22 may be substantially limited. Furthermore, in many instances the storage element 30 will be tamper resistant.

The processor 32 includes several modules, which in connection with at least some embodiments, are in the form of one or more sets of prestored instructions, which are executed by one or more microprocessors. More specifically, the processor 32 includes a reception module 34 and a validation module 36. hi some instances the storage element 30 containing the unique identifier 22 may be integrated as part of the one or more microprocessors forming all or part of the processor 32. In the same and/or other embodiments, all or parts of the various elements including the reception module 34 and the validation module 36 can be alternatively and/or partially implemented in hardware using discrete or integrated circuit elements, including logic gates and/or sequential state machines. Furthermore, to the extent that prestored instructions may be used, the prestored instruction can take the form of software instructions and/or microcode. However, one skilled in the art will readily appreciate that still further approaches are possible for implementing the same without departing from the teachings of the present invention.

The reception module 34 in at least one embodiment is coupled to the network 16, and is adapted for receiving the signed content including an associated certificate having a signature and an authorized device list verification extension field including a list of one or more identification entries, which match the unique identifiers of the one or more devices for which the certificate is valid. In at least some embodiments, having a list of one or more identification entries, which match the unique identifiers of the one or more devices for which the certificate is valid, involves an identification entry in the list, that is an exact match for the corresponding unique identifier. In other instances the identification entry may allow for values incorporating one or more wild card entries, which allows an identification entry to match more than one unique identifier.

However, in at least one embodiment, the number of matched unique identifier is limited. In some instances, the identification entries will be limited to entries which

only match devices, that are being used in connection with the development and/or the testing of an object. In at least one or more further embodiments, the maximum number of matched devices will correspond to a predetermined maximum number of devices, such as ten. In such an instance where the desired number of matched devices would necessarily exceed the maximum predetermined number of devices, the request and issuance of multiple certificates may be required.

In the illustrated embodiment, the validation module 36 is coupled to the reception module 34, and the storage element 30, and is more generally adapted for parsing the certificate for determining the validity of the certificate. The validation module 36 is further adapted for validating the signature of the content, if upon parsing the certificate, a match for the unique identifier is contained within a list of the one or more identification entries associated with the authorized device list extension field. In at least one embodiment, the authorized device list extension field has a corresponding enabled critical flag parameter, which requires that the validation module 36 parses the authorized device list extension field, where in the event that the validation module 36 is unable to parse the authorized device list extension field, the validation module 36 is unable to validate the signature of the content.

In at least one or more embodiments, one or more of the reception module 34 and the validation module 36 are trusted. FIG. 3 illustrates a block diagram of a certificate 50 including an authorized device list extension field 52, in accordance with at least one embodiment of the present invention. In addition to the authorized device list extension field 52, the certificate 50 additionally includes a signature 54, which is used in conjunction with a public key 56, also contained within the certificate, to validate the authenticity of the certificate 50. As noted above, the authorized device list extension field 52 can additionally include a critical flag parameter 58, which when enabled requires that the validation module 36 be able to parse the authorized device list 52, as part of authenticating the certificate 50.

In the illustrated embodiment, the certificate 50 additionally includes certificate identification and header information 60, which can take the form of metadata that additionally facilitates the identification, processing and parsing of the certificate. The certificate identification and header information 60 can include one or more elements, such as version information, a certificate serial number, a signature algorithm identifier,

the name of the issuer, a validity period, the subject name, and like information.

FIG. 4 illustrates a flow diagram of a method 100 for producing a certificate associated with an object, which is authorized for a predefined list of one or more devices, in accordance with at least one embodiment of the present invention. The method 100 includes identifying 102 a list of one or more devices for which the certificate is authorized, where each device has a unique identifier. An authorized device list extension field is then encoded 104, which includes a list of one or more identification entries, which comprises a match for each of the unique identifiers associated with the one or more identified devices. The authorized device list extension field is then associated 106 with the corresponding object.

In at least one embodiment, prior to associating 106 the authorized device list extension field with the corresponding object, a critical flag parameter is enabled 108, which corresponds to the authorized device list extension field.

FIG. 5 illustrates a flow diagram of a method 120 for confirming the authenticity of an object for a subset of devices, in accordance with at least one embodiment of the present invention. The method 120 includes comparing 122 the unique identifier for the device with the one or more entries in the authorized device list extension field. A determination 124 is then made as to whether a match exists between the unique identifier and one of the entries. If a match exists, then the authenticity of the object is confirmed 126. If a match does not exist, then the authenticity of the object is denied 128.

FIG. 6 illustrates a more detailed flow diagram of a method 126 for confirming the authenticity of an object, for use in connection with at least some of the embodiments illustrated in FIG. 5. In connection with the more detailed flow diagram, the method includes verifying 140 the validity of the signature associated with the certificate. A determination 142 is made as to whether the signature associated with the certificate is deemed to be valid. If the signature associated with the certificate is valid, the signature associated with the object is also verified 144. A determination 146 is then made as to whether the signature associated with the object is deemed to be valid. If both the signature associated with the certificate and the signature associated with the object are valid, then the object is authenticated 148. If one or both of the validity of the signature of the certificate and the validity of the signature of the object can not be

validated, then the authenticity of the object is denied 150.

In many instances the specific order in which the signature associated with the certificate and the signature associated with the object is validated is unimportant. Still in further instances, the validation of the certificate may involve the validation of a chain of certificates, where validation of the certificate is premised upon the validity of a corresponding certificate chain.

While the preferred embodiments of the invention have been illustrated and described, it is to be understood that the invention is not so limited. Numerous modifications, changes, variations, substitutions and equivalents will occur to those skilled in the art without departing from the spirit and scope of the present invention as defined by the appended claims.