Ex Parte Shackelford

Board of Patent Appeals and Interferences

May 31, 2007

09409617 (B.P.A.I. May. 31, 2007)

The opinion in support of the decision being entered today was not written
for publication and is not binding precedent of the Board.

UNITED STATES PATENT AND TRADEMARK OFFICE
____________

BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
____________

Ex parte DAVID MICHAEL SHACKELFORD
____________

Appeal 2007-0715
Application 09/409,617
Technology Center 2100
____________

Decided: May 31, 2007
____________

Before JAMES D. THOMAS, KENNETH W. HAIRSTON, and HOWARD
B. BLANKENSHIP, Administrative Patent Judges.

THOMAS, Administrative Patent Judge.

DECISION ON APPEAL
This appeal involves claims 1-40. We have jurisdiction under
35 U.S.C. §§ 6(b) and 134(a).
Representative independent claim 1 is reproduced below as best
representative of the disclosed and claimed invention:
1. A method for distributing computer software from a first
computer system, comprising the first computer system performing:
Appeal 2007-0715
Application 09/409,617

maintaining keys of computer systems authorized to access software
to be distributed;

receiving a request for software from a second computer system;

generating a message;

encrypting the generated message;

transmitting the encrypted message to the second computer system;

receiving an encrypted response from the second computer system;

determining whether there is one maintained key for the second
computer system capable of decrypting the received encrypted response;

decrypting the encrypted response with the determined key if there is
one determined key;

determining whether the decrypted response includes a part of the
generated message transmitted to the second computer system, wherein the
second computer system is authorized to access the software if the decrypted
response includes the part of the generated message and wherein the second
computer system is not authorized to access the software if there is not one
maintained key for the second computer system that is capable of decrypting
the encrypted response or the decrypted response does not include the part of
the generated message transmitted to the second computer system; and

permitting the second computer system access to the software after
determining that the second computer system is authorized to access the
software.

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Application 09/409,617

The following references are relied on by the Examiner:
Davis US 5,473,692 Dec. 5, 1995
Komuro1 US 5,991,307 Nov. 23, 1999
(filed Mar 28, 1997)
Takahashi US 6,195,432 B1 Feb. 27, 2001
(filed Mar. 10, 1997)
Schneier “Applied Cryptography, Second Edition”, 1996, pp. 44-46

Claims 1, 2, 8-14, 16, 17, 21-28, and 34-40 stand rejected under 35
U.S.C. § 102(b) as being anticipated by Davis. Claims 3-7, 15, 18-20, and
29-33 stand rejected under 35 U.S.C. § 103(a). As evidence of obviousness,
the Examiner relies upon Davis alone for claims 3, 18, and 29. The
Examiner combines Davis with Schneier for claims 4, 15, 19, and 30. Davis
is combined with Komuro for claims 5, 6, 31, and 32. Davis is also
combined with Takahashi for claims 7, 20, and 33.
Rather than repeat the positions of the Appellant’s and the Examiner,
reference is made to the Brief and Reply Brief for the Appellant’s positions,
and to the Answer for the Examiner’s positions.

OPINION
We reverse.
Regarding the rejection of representative claims 1 and 12, Appellant’s
arguments regarding which key is used by Davis to decrypt the message
having the challenge/response are persuasive. We reverse the rejection

1 Section 8 and page 10 of the Answer inadvertently identified the Komuro
reference as 5,994,307.
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Application 09/409,617

under 35 U.S.C. § 102(b), and since all rejections under 35 U.S.C. § 103(a)
rely on Davis, those rejections are also reversed.
Appellant argued independent claims 1, 16, and 27 collectively, and
since they recite substantially identical subject matter, they will be discussed
together.
Regarding claim 1, attention should be drawn to the following
limitations:
determining whether there is one maintained key for the
second computer system capable of decrypting the received
encrypted response;
decrypting the encrypted response with the determined
key if there is one determined key (emphasis added).

At page 3 of the Answer, the Examiner points to col. 8, lines 54-58 of
Davis as anticipating the above quoted limitations. At pages 11-12 of the
Answer, the Examiner also points to col. 5 of Davis, particularly lines
47-56, as anticipating the above quoted determining step.
In col. 8, Davis discloses a similar challenge-response authentication
procedure for establishing secure communications. Davis discloses
exchanging public keys between two hardware agents (col. 8, lines 33-44).
To provide proper context for the following discussion of Davis, it should be
noted that the first and second hardware agents disclosed by Davis have
been interpreted by Appellant and the Examiner as corresponding to the
claimed second and first computer systems, respectively.
In col. 8 of Davis, a challenge message is sent from the second
hardware agent to the first hardware agent (col. 8, lines 45-49). The first
hardware agent generates a response message by encrypting the challenge
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Application 09/409,617

message with the public key (the key previously received from the second
hardware agent) of the second hardware agent (col. 8, lines 49-54). The
response is sent to the second hardware agent, which decrypts the response
using the private key of the second hardware agent, which has not been
exchanged and is maintained only in the second hardware agent.
It is clear that the private key of the second hardware agent is not
“maintained” for the second computer system (first hardware agent), and
since the private key is used to decrypt the response message, the above
quoted limitation is not anticipated by Davis.
In col. 5, Davis discloses that “SK and PUK1 keys 60 and 11 are used
to decrypt the encrypted original message 65 and the digital signature 80 to
retrieve the transmitted message digest 75 and the original message 40,
respectively.” (col. 5, lines 52-56). Also in col. 5, Davis discloses that the
original message 40 is encrypted using “a symmetric secret key (“SK”) 60
via the DES algorithm to form the encrypted message 65” (col. 5, lines
33-36).
It is clear that this section of Davis does not disclose decrypting a
transmitted message using an exchanged public key or a key “maintained”
for a second computer system. In this section of Davis, the public key of the
node initiating the communication is used only to decrypt the digital
signature, which was previously encrypted using the private key of the
initiating node and a message digest (col. 5, lines 40-43). The actual
message is decrypted using the symmetric secret key, and it was previously
encrypted using the secret key (col. 5, lines 33-35).
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Furthermore, it is clear from the cited teachings at col. 5. of Davis that
these techniques are not used in the challenge-response sequence used to
establish secure communications in col. 8. There is no discussion of the
symmetric secret key from col. 5 discussed anywhere in the description of
the challenge-response sequence at col. 8. The Examiner appears to
recognize this discrepancy, stating that the additional protocols disclosed in
col. 5 “can be used for additional authentication” (page 12 of the Answer).
While it may be true that they “can be used”, Davis chose not to do so in his
disclosed method.
As mentioned above, claims 16 and 27 substantially correspond to
claim 1, and the rejection of those claims is reversed for the same reasons as
discussed above.
Appellant argued independent claims 12 and 25 collectively, and since
they recite substantially identical subject matter, they will be discussed
together.
Regarding claim 12, attention should be drawn to the following
limitations, performed by “the second computer”:
providing a key to the first computer system capable of
decrypting an encrypted response from the second computer
system;
encrypting the response message, wherein the encrypted
response message is capable of being decrypted by the provided
key at the first computer system (emphasis added).

At pages 4-5 of the Answer, the Examiner points to col. 7, lines 44-45
as anticipating the providing step and col. 8, lines 50-54 as anticipating the
encrypting step.
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Application 09/409,617

The disclosure in col. 7 of Davis describes a manufacturing process
and discloses sending a public key to a certification system (col. 7, lines
43-46). The certification system compares the public key to previously
generated keys “to ensure that each public/private key pair is unique” (col. 7,
lines 46-54). The Examiner has interpreted the certification system as
anticipating the claimed “first computer system” (page 4 of the Answer).
Col. 8 discusses the challenge-response sequence discussed above
regarding claim 1. The cited portion states that the “first hardware system
… generates a response message by encrypting the decrypted challenge
message with the public key of the second hardware agent”. However, it is
clear that the “first hardware system” is not the same as the “certification
system” disclosed in col. 7. The only role of the certification system is to
verify that generated keys are unique during the manufacturing process. It is
simply not used in the disclosed challenge-response sequence.
There is no disclosure in Davis of providing a key to a first computer
system, and subsequently transmitting a response message to the first
computer that is capable of being decrypted using the key that was
previously provided. Instead, in Davis, the first hardware agent encrypts the
message so that it may be decrypted with the private key of the second
hardware agent, and not decrypted with a key the second computer system
provides to the first computer system as claimed, as noted by Appellant
(pages 11-12 of the Brief).
As mentioned above, claim 25 substantially corresponds to claim 12,
and the rejection of those claims is reversed for the same reasons as
discussed above.
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Application 09/409,617

In summary, we reverse the Examiner’s rejection of claims 1, 2, 8-14,
16, 17, 21-28, and 34-40 under 35 U.S.C. § 102(b). Accordingly, the
rejections of the remaining claims under 35 U.S.C. § 103(a) are reversed as
well. Therefore, the decision of the Examiner is reversed.

REVERSED

pgc

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