Source: http://www.google.com.br/patents/US6247026
Timestamp: 2018-01-19 19:34:52
Document Index: 756828625

Matched Legal Cases: ['art 2', 'art 2', 'art 2', 'art 1', 'art 2', 'art 1']

Patente US6247026 - Method, apparatus, and product for leasing of delegation certificates in a ... - Patentes do Google
A method, apparatus, and product for leasing a delegation certificate in a distributed processing system is provided. Consistent with this method, apparatus, and product, a delegatee requests from a delegator access to a resource for a period of time that the delegator has authority to access. Responsive...http://www.google.com.br/patents/US6247026?utm_source=gb-gplus-sharePatente US6247026 - Method, apparatus, and product for leasing of delegation certificates in a distributed system
Número da publicação US6247026 B1
Número do pedido US 09/044,838
Data de publicação 12 jun. 2001
Data de depósito 20 mar. 1998
Data da prioridade 11 out. 1996
Também publicado como CN1298509A, EP1062580A1, WO1999044130A1
Número da publicação 044838, 09044838, US 6247026 B1, US 6247026B1, US-B1-6247026, US6247026 B1, US6247026B1
Inventores James H. Waldo, Ann M. Wollrath, Robert Scheifler
Citações de patente (128), Citações de não patente (103), Citada por (62), Classificações (53), Eventos legais (4)
US 6247026 B1
A method, apparatus, and product for leasing a delegation certificate in a distributed processing system is provided. Consistent with this method, apparatus, and product, a delegatee requests from a delegator access to a resource for a period of time that the delegator has authority to access. Responsive to this request, the delegator determines an appropriate lease period during which time the delegatee has authority to access to the resource.
Reivindicações(46)
1. A method in a processing system, comprising the steps of:
receiving a lease request from a program, the lease request specifying a resource and a requested lease period;
determining a lease period during which the program has authority to access the resource; and
sending to the program a delegation certificate for use by the program to access the resource during the determined lease period.
2. A method for managing a resource in a system that includes a client, a server that manages the resource, and a delegator authorized to use the resource, said method comprising the steps of:
the client receiving from the delegator a lease that delegates to the client use of the resource for a lease period; and
the server providing the client with access to the resource for the lease period.
3. The method of claim 2, wherein the receiving step includes the step of:
requesting by the client a lease from the delegator for using the resource.
4. The method of claim 2, wherein the receiving step includes the step of:
providing by the delegator to the client a delegation certificate that delegates to the client the delegator's authority to use the resource.
5. The method of claim 2, wherein the providing step includes the step of:
identifying an identity of the client by invoking code provided by the delegator to the client.
6. The method of claim 2, wherein the providing step includes the step of:
authenticating an identity of the client by invoking code provided by the delegator to the client.
7. The method of claim 2, wherein the providing step includes the step of:
the client managing the lease by invoking code provided by the delegator to the client.
8. A method for managing a resource in a system that includes a client, a server that manages the resource, and a delegator authorized to use the resource, said method comprising the steps of:
the client requesting from the delegator a lease for using the resource;
the delegator granting the requested lease to the client for a lease period; and
the client using the resource for the lease period.
9. The method of claim 8, wherein the granting step includes the step of:
determining the lease period during which the client is authorized to use the resource.
10. The method of claim 8, wherein the granting step includes the step of:
providing to the client a delegation certificate that authorizes the client to use the resource for the granted lease period.
11. The method of claim 8, wherein the granting step includes the step of:
providing to the client a method for identifying the client as the delegator to the server.
12. The method of claim 8, wherein the granting step includes the step of:
providing to the client a method for use by the server for authenticating identification of the client.
13. The method of claim 12, wherein the providing step includes the step of:
providing to the client an authentication method that uses a public key.
14. The method of claim 12, wherein the providing step includes the step of:
providing to the client an authentication method that uses a challenge-response protocol.
15. The method of claim 12, wherein the providing step includes the step of:
providing to the client an authentication method that uses a shared secret method.
16. The method of claim 8, wherein the granting step includes the step of:
providing to the client a method for determining a type of access to the resource authorized by the delegator.
17. The method of claim 8, wherein the granting step includes the step of:
providing to the client a method for use by the server for determining a type of access that the server grants to the client for using the resource when the client requests from the server access to the resource.
18. The method of claim 8, wherein the granting step includes the step of:
providing to the client a method for use by the server for determining the lease period.
19. The method of claim 8, wherein the granting step includes the step of:
providing to the client a method for canceling the granted lease when the client completes using the resource.
20. The method of claim 8, wherein the granting step includes the step of:
providing to the client a method for renewing the granted lease when the lease period is near expiration.
21. The method of claim 8, wherein the using step includes the step of:
the client requesting from the server access to the resource according to the granted lease.
22. The method of claim 8, further comprising the step of:
reclaiming the resource by the server when the client cancels the granted lease.
23. The method of claim 8, further comprising the step of:
reclaiming the resource by the server when the granted lease expires.
24. The method of claim 8, further comprising the step of:
the delegator requesting from the client to perform a task that requires use of the resource.
25. The method of claim 8, wherein the using step includes the step of:
the client requesting from the server access to the resource.
26. The method of claim 8, wherein the using step includes the step of:
authenticating by the server, based on a delegation certificate provided by the delegator, an identity of the client when the server receives a request from the client to use the resource.
27. The method of claim 8, wherein the using step includes the step of:
the server determining, based on a delegation certificate provided by the delegator, a type of access by the client to the resource.
a client program containing first code that requests a lease for accessing a resource;
a delegator program having access to the resource and containing second code for granting the lease to the client for a lease period by providing the client program with a delegation certificate; and
a server program containing third code for granting access by the client to the resource based on the delegation certificate; and
a processor for running the client program, the server program, and the delegator program.
a requesting means for requesting access to a resource;
a delegation means for delegating to the requesting means an authorization to access the resource; and
a resource allocating means for granting access by the requesting means to the resource based on the delegated authorization.
30. A computer-readable memory device encoded with a data structure for using a resource in a system including a client, a server that manages the resource, and a delegator authorized to access the resource, the data structure comprising:
an object including:
a first method for identifying the client to the server as the delegator when the client requests from the server access to the resource;
a second method for authenticating identification of the client;
a third method for determining type of access by the client to the resource and duration of access by the client to the resource; and
a fourth method for managing access by the client to the resource.
31. The computer-readable memory device of claim 30, wherein the fourth method includes a method for renewing a lease granted by the delegator to the client for accessing the resource.
32. The computer-readable memory device of claim 30, wherein the fourth method includes a method for canceling a lease granted by the delegator to the client for accessing the resource.
33. A computer-readable medium containing instructions for controlling a data processing system to perform a method, the data processing system including a client, a server that manages a resource, and a delegator authorized to access the resource, said method comprising the steps of:
the delegator providing to the client a delegation certificate that grants the lease to the client for a lease period; and
the server granting access to the resource by the client based on the delegation certificate.
34. The computer-readable medium of claim 33, further comprising the step of:
managing by the client the granted lease using the delegation certificate.
35. The computer-readable medium of claim 33, wherein the providing step includes the step of:
providing to the client a method for determining duration of the granted lease period.
36. The computer-readable medium of claim 33, wherein the providing step includes the step of:
providing to the client a method for determining a type of access authorized by the delegator.
37. The computer-readable medium of claim 33, wherein the providing step includes the step of:
providing to the client a method for renewing the granted lease.
38. The computer-readable medium of claim 33, wherein the providing step includes the step of:
providing to the client a method for canceling the granted lease.
39. The computer-readable medium of claim 33, wherein the granting step includes the step of:
invoking a method in the delegation certificate to determine identity of the client.
40. The computer-readable medium of claim 33, wherein the granting step includes the step of:
invoking a method in the delegation certification to authenticate identification of the client.
41. The computer-readable medium of claim 33, wherein the granting step includes the step of:
invoking a method in the delegation certificate to determine a type of access by the client to the resource.
42. The computer-readable medium of claim 33, wherein the granting step includes the step of:
invoking a method in the delegation certificate to determine duration of the granted lease period.
43. A method for using a resource in a system that includes a client, a server that manages the resource, and a delegator authorized to use the resource, said method comprising the steps of:
the client requesting from the delegator a lease for accessing the resource;
the client receiving from the delegator a lease object that delegates an authorization to use the resource for a lease period; and
the client accessing the resource according to the delegated authorization.
the client managing the lease by invoking one or more methods in the lease object.
45. A method for managing a resource in a system that includes a client, a server that manages the resource, and a delegator authorized to use the resource, said method comprising the steps of:
the delegator receiving from the client a request for a lease for accessing the resource; and
the delegator providing a lease object that delegates to the client an authorization to use the resource for a lease period.
46. A method for managing a resource in a system that includes a client, a server that manages the resource, and a delegator authorized to use the resource, said method comprising the steps of:
the server receiving from the client a request for accessing the resource, the request having an associated lease object that delegates to the client an authorization from the delegator to access the resource for a lease period;
the server authenticating the request by invoking a first method on the lease object;
the server determining the lease period by invoking a second method on the lease object;
the server determining a type of access by the client to the resource by invoking a third method on the lease object; and
the server providing the client with access to the resource when the request is authenticated, the lease period is active, and the type of access is authorized.
This is a continuation-in-part of U.S. patent application Ser. No. 08/729,421, filed on Oct. 11, 1996, U.S. Pat. No. 5,832,529, which is incorporated herein by reference.
U.S. patent application Ser. No. 09/044,923, entitled “Method and System for Leasing Storage,” pending, and filed on the same date herewith.
U.S. patent application Ser. No. 09/044,834, entitled “Method, Apparatus and Product for Leasing of Group Membership in a Distributed System,” pending, and filed on the same date herewith.
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This invention generally relates to data processing systems and, more particularly, to leasing delegation certificates in data processing systems.
In accordance with the present invention, referential integrity is guaranteed without costly memory leaks by leasing resources for a period of time during which the parties in a distributed system, for example, an application holding a reference to a resource and the garbage collection system managing that resource, agree that the resource and a reference to that resource will be guaranteed. At the end of the lease period, the guarantee that the reference to the resource will continue lapses, allowing the garbage collection system to reclaim the resource. Because the application holding the reference to the resource and the garbage collection system managing the resource agree to a finite guaranteed lease period, both can know when the lease and, therefore, the guarantee, expires. This guarantees referential integrity for the duration of a reference lease and avoids the concern of failing to free the resource because of network errors. In addition to memory, the leasing technique can be applied to delegation certificates.
Consistent with an alternative embodiment of the present invention, as embodied and broadly described herein, a method for leasing delegation certificates is provided. This method comprises the steps of receiving a lease request from a client specifying a resource and a lease period, determining a lease period during which the client has authority to request from a server access to the resource, advising the client of the granted lease period, granting the client a delegation certificate which the client can use to access the resource from the server.
FIG. 9 is a diagram of a data processing system for leasing delegation certificates in a distributed processing system that can be used in an alternative embodiment of the present invention; and
FIG. 10 is a flow diagram of the steps performed by the delegator process when another process (potential delegatee) requests a lease according to an alternative embodiment of the present invention; and
FIG. 11A and FIG. 11B represent a flow diagram of the steps performed by a process (potential delegatee) when requesting a lease from the delegator process according to an alternative embodiment of the present invention; and
FIG. 12 is a flow diagram of the steps performed by the server when a delegatee requests access to a resource according to an alternative embodiment of the present invention.
Operating systems 740, 840, and 940 are standard operating systems tied to the corresponding processors 710, 810, and 910, respectively. The platforms 700, 800, and 900 can be heterogeneous. For example, platform 700 has an UltraSparc® microprocessor manufactured by Sun Microsystems Corp. as processor 710 and uses a Solaris® operating system 740. Platform 800 has a MIPS microprocessor manufactured by Silicon Graphics Corp. as processor 810 and uses a Unix operating system 840. Finally, platform 900 has a Pentium microprocessor manufactured by Intel Corp. as processor 910 and uses a Microsoft Windows 95 operating system 940. The present invention is not so limited and could accommodate homogenous platforms as well.
MI components 1030 and 1130 each include a server call processor 1031 and 1131, respectively, an application call processor 1032 and 1132, respectively, and a garbage collector 1033 and 1133,respectively. Each of the MI components 1030 and 1130 also contains reference components, including reference data portions 1034 and 1134, respectively, reference counts 1035 and 1135, respectively, and grant period registers 1036 and 1136, respectively, for each reference that the respective MI component 1030 or 1130 monitors.
The leasing technique, described above, relates to garbage collection. However, an alternative embodiment of the present invention, as described below, can be used with delegation certificates.
A delegation certificate allows one actor (“a delegator”) with sufficient privilege to access a resource to delegate its authority to access this resource to another actor (“a delegatee”) who then accesses the resource on behalf of the delegator.
However, for security purposes, the delegator may not want to delegate to the delegatee carte blanche permission to access the resource for fear the delegatee may abuse its privilege either intentionally or unintentionally. Thus, the delegator may want to impose limits on the delegatee's access, such as the type of access permitted or the length of time access is permitted. The leasing of delegation certificates allows the delegator to control and limit the delegatee's access, thus providing additional security.
Delegation certificates can be leased to access various resources, such as files. An example of a delegation follows: a delegator may have confidential tax files managed by a file system manager. By prior negotiation, the file system manager will only grant access to these files to the owner, the delegator. However, the owner may need the taxes to be calculated by a tax program, so the owner delegates authority to the tax program, the delegatee, to access the tax files for a limited time, until April 15. Accordingly, the owner grants the tax program permission, via a delegation certificate, to access the files controlled by the file system manager until April 15th. This is accomplished by leasing the delegation certificate to the tax program such that the lease expires on April 15th. If the tax program attempts to access the file after this date, the lease expires and it is prevented from doing so by the file system manager.
The leasing of delegation certificates allows the owner to control or limit access to the files by the tax program. More specifically, the tax program requests a lease from the owner for access to the files stored with the file system manager for read access until April 15th. If a lease is granted, the owner sends to the tax program a delegation certificate that indicates the tax program is entitled to read-only access to the owner's files.
The file system manager has the responsibility of authenticating the delegation certificate as well as to determine the type and length of the tax program's access. At no time can the tax program directly change the contents of the delegation certificate. However, the tax program can request the owner to renew the lease (i.e., if the tax program requires additional time to access the file) or to cancel the lease, (i.e., if the tax program's access is completed before the lease period expires).
The delegation certificate is an object that proves the identity of the delegator and has a set of corresponding rights attached to it. In particular, the delegation certificate object contains a principal identifier, some means for proving the identification, and a specification of the rights. The specification of the rights includes methods for determining the type of access requested and the duration of a lease. In addition, the object includes methods for canceling a lease and for renewing a lease. Finally, the methods may generate exceptions that, when accessed, set forth the reason why invocation of the method was unsuccessful.
The object is an instance of a class that may be extended in many ways to offer more functionality, but the basic class is defined as follows:
public void getIdentfier ();
public void getAuthentication ();
public void getAccesstype ();
public long getDuration ();
public void cancel () throws
The principal identifier gives the delegatee the appearance of being the delegator when the delegatee communicates with the system manager. The integrity of the identification is assured by any number of known authentication methods, such as public-key, challenge-response protocol, or shared secret technology.
Invoking the access type method provides the type of access the delegator permits. This method can be invoked by whoever has the delegation certificate, either the delegator, the delegatee, or the file system manager. For instance, the delegates will invoke the method to determine what type of access it is permitted to seek from the file system manager. The file system manager will invoke the method to determine what type of access it is permitted to grant. For example, the delegator may deem a particular file as read-only access. In this case, the file system manager will only allow read access for a subsequently granted lease for that particular file. Conversely, an attempt by the delegatee to write to that storage location would not be permitted by the file system manager.
Invoking the duration method provides the length of the granted lease period. This period represents the most recent lease granted by the delegator.
The renew method permits the renew of the lease, asking for more time, without having to re-initiate the original lease request. Situations where the delegatee may desire to renew the lease include when the original lease proves to be insufficient (i.e., the delegatee requires additional use of the storage location), or when only a partial lease (i.e., less than the requested lease) is granted.
In addition, the renew method can be continually invoked in order to obtain sequential lease periods. The renew method, however, cannot be invoked if the delegatee does not have an active lease. Also, the renew method has no return value; if the renewal is granted, the new lease period will be reflected in the lease object on which the call was made. If the delegator is unable or unwilling to renew the lease, the reason is set forth in the LeaseDeniedException generated by the renew method.
The cancel method is invoked when there is still time left on the lease, but the delegatee no longer desires access. The cancel method may also be invoked by the delegator if, for instance, it wants to cancel the delegatee's access. Thus, cancel allows the file, for example, to be reclaimed. In contrast, upon the end of a lease, (i.e., natural termination occurs), there is no notification obligation by the delegatee.
FIG. 9 depicts a data processing system 9000 suitable for use for by an alternative embodiment of the present invention. The data processing system 9000 includes a computer system 9002 connected to the Internet 9004. The computer system 9002 includes a memory 9010, a secondary storage device 9018, a central processing unit (CPU) 9024, an input device 9026, and a video display 9022. The secondary storage device 9018 further includes a number of files 9020. The memory 9010 further includes a delegator program 9008, a delegatee program 9010, and an operating system 9014 containing a file system manager 9016. The file system manager 9016 manages files 9020 on the secondary storage device 9018. The delegates 9010 requests access to a secondary storage device 9018 by requesting a lease from the delegator 9008. In response, the delegator 9008 may either grant or deny the lease as further described below. If the delegator 9008 grants the lease to the delegatee 9010, the delegatee 9010 then requests access to the secondary storage device 9018 from the file system manager 9016. One skilled in the art will appreciate that computer 9000 may contain additional or different components.
Although aspects of the alternative embodiment are described as being stored in memory 9010, one skilled in the art will appreciate that these aspects may also be stored in other computer readable media, such as secondary storage devices, like hard disks, floppy disks, or CD-ROM; a carrier wave from the Internet 9004; or other forms of RAM or ROM.
FIG. 10 depicts a flow chart of the steps performed by the delegator 9008 when receiving a lease request from the delegatee 9010. The first step performed by the delegator is to request the delegatee to access a resource, such as a file, on the delegator's behalf (step 10002). At some point later, the delegator will receive a lease request from the delegates (step 10004). This request is a function call that includes a number of parameters including (1) the requested file the delegatee wishes to lease, (2) the desired lease period, and (3) the type of access the delegates desires.
The requested file parameter contains an indication of the file to be leased. The desired lease period contains an amount of time the delegatee wants to utilize the file. The type of access requested indicates the type of access the client requested. For example, the delegatee may request read access or write access. To form a valid request, the delegatee request must contain both the file desired and the desired lease. After receiving the request, the delegator examines the parameters to verify the propriety of the request (step 10006).
After examining the parameters, the delegator determines if the request is, in fact, proper (step 10008). For example, the delegator checks if the requested file is a file that the delegator has the ability to lease. Also, the delegator verifies that some lease period is specified. Additionally, the delegator checks if the type of access requested is available. If the delegator determines that the lease request is improper, the delegator generates an exception (step 10010) and processing ends.
If the delegator determines that the lease request is proper, the delegator determines a sufficient lease period (step 10012). For example, if access to the delegator's tax files are requested, the delegator may grant a lease period up to April 15. Next, the delegator creates a lease object and returns the object to the delegatee (step 10020) and processing ends.
FIGS. 11A and 11B depict a flowchart of the steps performed by the delegatee 9010 when requesting a lease from the delegator 9008. The first step performed by the potential delegatee is to receive a request by the delegatee that entails accessing a file on the delegator's behalf (step 11001). At some point later, the delegatee sends a request for a lease to the delegator (step 11002). This request is a function call and is described in step 10004 in FIG. 10.
After sending the request, the delegatee receives a lease object from the delegator (step 11004). The lease object, as described above, includes the principal identifier, the authentication method, the access-type method, the lease duration method, the renew method, the cancel method.
Next, the delegatee, by examining the lease object, determines if a lease was granted (step 11006). If the delegatee determines that a lease was not granted, the delegatee invokes the exception method (step 11008), which allows the delegatee to determine why a lease was not granted. If the delegatee determines that the lease was not granted because of an improper request (step 11010), the delegates reconfigures the request (step 11012), and processing continues to step 11002. However, if the delegatee determines that the lease was not granted for reasons other than an improper request, processing ends. Note, the delegator may grant multiple leases to the same file, since it is ultimately the responsibility of the file system manager to referee actual access to the file.
If the delegatee, in step 11006, determines that a lease was granted by the delegator, next the delegates requests access to the file from the file system manager, by sending an access request (step 11018). Processing then continues to step 11020 in FIG. 11B.
After the delegatee sends the access request to the file system manager in step 11018 in FIG. 11A, the delegatee determines, by examining the lease object, if the file system manager granted the delegatee access to the file (step 11020). If the delegates determines that access was not granted by the file system manager, the delegatee invokes the exception method, contained in the object returned by the file system manager, which allows the delegatee to determine why access was not granted (step 11022).
If the delegatee determines that access was not granted because of an improper request (step 11024), processing ends. On the other hand, if the request was proper, the delegatee determines if access was not granted because the file system manager allocated the file to another leaseholder (step 11026). If the delegatee determines the file is busy, the delegatee waits for a predetermined period of time (step 11028) and processing continues to step 11018 in FIG. 11A. If the delegatee determines that access to the file was denied for some other reason, processing ends.
If the delegatee determines, in step 11020, that the file system manager granted the delegates access to the file, then the delegates can access the file (step 11030). Next, the delegatee determines if it is finished accessing the file (step 11032).
If the delegatee's use is completed, the delegatee determines if the lease expired, (i.e., the lease is no longer active) (step 11034). If the lease expired, processing ends and no communication is necessary between the delegatee and the file system manager (i.e., natural termination occurs). Otherwise, if the lease is still active the delegatee invokes the cancel method (step 11036). The delegatee accesses the cancel method via the lease object. The cancel method informs the file system manager and the delegator that the delegatee is no longer interested in the file. Accordingly, the cancel method allows the file system manager to reclaim the file for use by other lease holders in an expeditious fashion.
If the delegatee determines in step 11032 that it still desires access to the file, the delegatee determines if the lease is about to expire (step 11038). This is achieved by the delegatee comparing the duration of the lease with current time minus the time when the lease was granted. The duration of the lease is found by invoking the duration method. If the lease is not about to expire, the delegatee continues to access the file (step 11030).
However, if the lease is about to expire in step 11038, the delegatee must decide whether or not to renew the lease (step 11040). If the delegatee chooses to renew the lease, the delegatee invokes the renew method of the lease object. If the renew method is invoked, processing continues to step 11002 in FIG. 11A. If the delegates does not renew the lease, then processing ends and no communication is necessary between the delegatee and the file system manager (i.e., natural termination occurs).
FIG. 12 depicts a flow chart of the steps performed by the file system manager 9016 when a delegatee process 9008 requests access to a file. The first step performed by the file system manager is to receive an access request by the delegatee (step 1202). After receiving the request, the file system manager authenticates the delegatee's identity by invoking the principal identifier method and the authentication method, via the lease object (step 1203). If the file system manager determines that the delegatee's lacks the proper identity to access the file (step 1204), the file system manager generates an exception (step 1206) and processing ends.
If the file system manager determines in step 1204 that the delegatee's identity is authentic, the file system manager invokes the getAccess type method (step 1208). By invoking the getAccess type method, the file system manager is able to determine which type of access the delegatee desires. Next, the file system manager determines if the file is available for the type of access requested (step 1210). If the file system manager determines that the file is unavailable, the file system manager generates an exception (step 1206) and processing ends.
If the file system manager determines, in step 1210, that the file is available, the file system manager invokes the duration method (step 1212). The file system manager invokes the duration method in order to determine if there is time left on the delegatee's lease. If the file system manager determines that the delegatee's lease is active (step 1214), the file system manager grants the delegatee access to the file (step 1218). After granting the delegatee access to the file, the file system manager returns to step 1212.
If the file system manager determines in step 1214 that the lease is not active, the file system manager will reclaim the file (step 1216). After reclaiming the file, the file system manager generates an exception (step 1206) and processing ends.
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Classificação nos Estados Unidos 1/1, 711/E12.006, 711/E12.009, 711/E12.01, 718/104, 709/203, 707/999.206, 707/999.202, 707/999.201, 707/999.01, 707/999.009
Classificação internacional G06F12/02, G06F15/16, G06F12/00, G06F9/46, H04L12/417, G06F17/30, H04L12/433, G06F9/445, H04L29/06, G06F9/50
Classificação cooperativa Y10S707/99939, Y10S707/99953, Y10S707/99957, Y10S707/99952, G06F9/50, H04L29/06, G06F12/0261, G06F9/468, G06F9/548, H04L12/433, G06F9/5061, G06F9/547, G06F9/465, G06F9/4411, G06F17/30607, G06F12/0253, G06F12/023, H04L69/24, G06F2209/462
Classificação europeia G06F9/50, G06F9/54P, G06F9/54P1, G06F9/46V, G06F9/44A4, H04L12/433, G06F12/02D2G, G06F17/30S8T, G06F9/46M, G06F12/02D2G2, G06F12/02D2, H04L29/06, G06F9/50C
28 jul. 1998 AS Assignment
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:WALDO, JAMES H.;WOLLRATH, ANN M.;SCHEIFLER, ROBERT;REEL/FRAME:009346/0757;SIGNING DATES FROM 19980717 TO 19980720
9 nov. 2004 FPAY Fee payment