Friday, 15 January 2016

T 108/12 A divisional application in the inescapable trap



The application of this appeal procedure is a divisional application. The Opponent argued during the Opposition procedure and during the Appeal Procedure that the divisional application extends beyond the disclosure of the mother application. This case shows once again that one has to be careful in changing something in the divisional application. The details of this case are a little bit mathermatical and the reasoning of the Board is strongly based on what would the skilled person in the field of security/encryption consider to be the teaching of the original application. One point of discussion is: Does the mother application provide enough support for  f(α)=f'(α) (as claimed in the divisional application), if the mother application teaches f(α)=f'(α)=α? Another point of discussion was: Does the mother application provide enough support for "a specific signature is kept private" (as claimed in the divisional application) while the mother application discloses that, in certain embodiments, the signature is not transmitted.
Ok, there were problems with support of the divisional application in the mother application, but the proprietor finally ends up in the inescapable trap. It is somehow sad to end up in the inescapable trap.


Summary of Facts and Submissions


I. This appeal is against the interlocutory decision of the Opposition Division of the European Patent Office posted on 24 November 2011, maintaining the European patent No. 1768300 in amended form.

[...]

V. Independent claim 1 of the main request as filed with letter dated 28 August 2015, corresponding to the patent as granted, reads:
"1. A method of establishing a session key between a pair of correspondents A,B in a public key data communication system to permit exchange of information therebetween over a communication channel, each of said correspondents having a respective private key a,b and a public key pA, pB derived from a generator alpha and respective ones of said private keys a,b, said method including the steps of:
i) a first of said correspondents A selecting a first random integer x and exponentiating a first function f(α) including said generator to a power g(x) to provide a first exponentiated function f(α)g(x) ;
ii) said first correspondent A generating a first signature SA from said random integer x said exponentiated function f(α)g(x) and said private key a to bind said integer x and said private key a, said first correspondent A maintaining said first signature private to itself;
iii) said first correspondent A forwarding to a second correspondent B a message including said first exponentiated function f(α)g(x);
iv) said correspondent B selecting a second random integer y and exponentiating a second function f(alpha) including said generator to a power g(y) to provide a second exponentiated function f(α)g(y) and generating a signature SB obtained from said second integer y and said second exponentiated function f(α)g(y) and said private key b to being [sic] said integer y and said private key b, said second correspondent B maintaining said second signature SB private to itself;
v) said second correspondent B forwarding a message to said first correspondent A including said second exponentiated function f(α)g(y); and
vi) each of said correspondents constructing a session key K by exponentiating information made public by the other correspondent with information that is private to themselves whereby subsequent decryption of information confirms establishment of a common key and thereby the identity of said correspondents."


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Reasons for the Decision

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2. Articles 100(c), 76(1) and 123(2) EPC


Since the patent in suit is based on a divisional application, according to Article 100(c) EPC the granted set of claims must find a basis in the earlier (parent) application as filed, i.e. in document WO 98/18234 A1 (Article 76(1) EPC).
References to the original disclosure or original claims, description or drawings are to be understood as referring to the disclosure of the earlier application 96944186.4 as filed, published as WO 98/18234 A1.


Proprietor's main request


3. The decision under appeal followed the opponent's (appellant 2) request and rejected the main request of the proprietor, because claim 1 added subject-matter to the content of the earlier application as filed, contrary to the provisions of Article 100 c) EPC.


3.1 According to claim 1 of the main request a first function f(alpha) is exponentiated by the first correspondent A to provide a first exponentiated function f(α)g(x) (step i) and the second correspondent B exponentiates a second function which is the same function f(α) to provide a corresponding second exponentiated function f(α)g(y) (step iv). In original claim 1, however, the two functions and the basis in the two exponentiated functions were specified in a different way, namely f(α), f'(α) and f(α)g(x), f'(α)g(y), respectively.

3.2 The proprietor (appellant 1) argued that in all embodiments as well as according to original claim 7 the two functions f(alpha), f'(alpha) were indeed the same function f(alpha) and that in Original claim 1 the two functions were already meant to be the same. When reading original claim 1 together with any of the protocols/embodiments, it was clear that the functions could be the same and arbitrary (see e.g. page 6, point 3 of the statement setting out the grounds of appeal dated 4 April 2012). Therefore the embodiments and original claim 7 provided a basis for claim 1 of the main request.
The proprietor further argued that the feature that the functions f(α) and f'(α) could not only be the same, but could also be equal to the identity function f(α)=α, represented a further feature which was not essential to the solution of the problem solved by the invention, namely bandwidth reduction.


3.3 The board agrees with the decision under appeal which reasoned that the specification of f(α) and f'(α) in the original application implied the use of two different functions. Even if the wording of original claim 1 was interpreted to the effect that f(α) and f'(α) can be different functions as well as comprising the special case of both functions being the same, the limitation in present claim 1 to only having the same functions is a selection for which no direct and unambiguous disclosure is found.
Claims 6 and 7 of the earlier application provide a basis for a feature that f(α)=α and f'(α)=α. The board agrees with the opponent's argument that specifying that the two functions f(α) and f'(α) are arbitrary but the same is an intermediate generalisation between the special case that both functions are the identity function and the general case that the two functions are arbitrary and may be different. As the description does not contain any teaching as to the nature of these functions, apart from the fact that they may be the identity function, irrespective of the skilled person's knowledge of mathematics or cryptography there is no basis for an intermediate generalisation that the two functions are the same, arbitrary single function. Nor is there a basis for splitting the feature f(α)=f'(α)=α into a first feature that the functions are identical f(α)=f'(α) and a second feature that they are the identity function f(α)=f'(α)=α. This first feature without having the second feature at the same time constitutes new technical information that cannot be derived from the original application in the sense of decision T 461/05 referred to by both parties (see e.g. page 7 of the proprietor's statement setting out the grounds of appeal, and page 4 onwards of the opponent's letter dated 20 August 2012). In particular, the second feature is regarded as necessary for carrying out the invention and therefore cannot be regarded as non-essential.


3.4 In the board's judgement, there is no basis for removing the second feature as not essential. Consequently, claim 1 of the main request adds subject-matter to the original disclosure of the earlier application, contrary to Article 100 (c) EPC.


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Proprietor's auxiliary request 4


5. The opponent objected to claim 1 under Articles 123(2) (or 76(1), respectively) and 100(c) EPC with regard to step ii) of generating a first signature containing the additional formulation "said first correspondent A maintaining said first signature private to itself", and step iv) containing the corresponding formulation "said second correspondent B maintaining said second signature SB private to itself".

5.1 In the decision under appeal the basis for this amendment was found in protocols 1', 2', 1'', and 1''' of the original description, where it was argued that the signatures were in fact not transmitted, as well as in the passages "the signatures need not be transmitted" (page 8, lines 24-25), "the transmission of SA and SB is avoided" (page 9, line 5), "avoiding the need to transmit the signature" (page 10, lines 4-5), and "not necessary to send the signature components" (page 13, lines 13-14). Moreover, the last step of original claim 1 already referred to private information which corresponded to the signatures in protocols 1', 2', 1'', and 1'''.

5.2 The opponent essentially argued (see e.g. point I. 4 of the statement setting out the grounds of appeal and point II.2 onwards of letter dated 7 January 2013, repeated during oral proceedings) that in the original section "disclosure of the invention" on pages 4 and 5 of the original application the signature was explicitly transmitted to the correspondent, which was in contrast to the present set of claims. Private information was disclosed to be accessible to both correspondents A and B (see original claim 1, last line "information that is private to themselves" - emphasis added). The signature was not disclosed as private information, only the random number was to be held private (see original application, page 5, lines 1 to 3). With regard to the signature there were disclosed embodiments either with its transmission or without its transmission. Furthermore, the act of keeping something private would imply measures to keep the information secret, whereas not transmitting would merely avoid such an activity without further measures regarding secrecy.

5.3 The board concurs with the opponent's arguments, in particular that the information alleged to be private is rather the random integer than the signature itself (see original application, page 5, lines 1 to 3). Maintaining something private, i.e. secret, involves more than merely not transmitting such information. While there are several passages relating to different protocols directly and unambiguously disclosing that a transmission of the respective signatures SA and SB can be avoided (see e.g. "the signatures [...] need not be transmitted" on original page 8, lines 24-25; "the transmission of SA and SB is avoided" on original page 9, line 5; "avoiding the need to transmit the signature" on original page 10, lines 4-5 and "not necessary to send the signature components" on original page 13, lines 13-14), there is hence no direct and unambiguous disclosure for signatures SA and SB to be maintained private.


5.4 Therefore the original (earlier) application documents do not provide a direct and unambiguous disclosure for claim 1, step ii) of generating a first signature containing the additional formulation "said first correspondent A maintaining said first signature private to itself", and step iv) containing the corresponding formulation "said second correspondent B maintaining said second signature SB private to itself".


5.5 Independent claim 12 contains the same feature "maintaining the first signature private to itself" and therefore suffers from the same deficiency.


5.6 Claims 1 and 12 according to this request therefore do not fulfil the requirements of Article 100(c) and Article 76(1) EPC.


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Proprietor's auxiliary request 12


7. In claim 1 of this request, step ii) of generating a first signature in claim 1 as granted containing the formulation "said first correspondent A maintaining said first signature private to itself" has been replaced by "said first correspondent A avoiding transmission of said first signature". Likewise, step iv) of claim 1 containing the corresponding formulation "said second correspondent B maintaining said second signature SB private to itself" has been replaced by "said second correspondent B avoiding transmission of said second signature".


7.1 The opponent (appellant 2) objected to this amendment, on the ground that it constituted an undue broadening of the subject-matter of claim 1 as granted in contrast to the requirements of Article 123(3) EPC.


7.2 The proprietor (appellant 1) argued that the amendment was merely a redefinition of a term in language closer to that of the original application, and in which the skilled person would not see a different teaching. No inappropriate advantage was achieved in the light of the criteria mentioned in decision G 1/93 (EPO OJ 1994, 541).


7.3 The proprietor further argued that the objection was surprising, since it was raised for the first time during oral proceedings. The board did not agree in this regard, since the opponent had already referred to G 1/93 in the written proceedings (see e.g. grounds of appeal dated 23 March 2012, section 3.1 on pages 13 and 14) and the issue of a conflict between Articles 123(2) and 123(3) EPC therefore had already been raised before the summons for oral proceedings. The proprietor therefore had to be prepared to discuss this issue.


7.4 The board agrees with the opponent that according to the description of the earlier application only one embodiment actually mentions not sending signatures (see protocol 2'), but no measures are disclosed to actually ensure that signatures are not transmitted.
As mentioned above (see point 5.3) and as already stated in the annex to the summons for oral proceedings, keeping something private, i.e. secret, involves more than merely not transmitting such information. Claim 1 as granted encompasses realisations where signatures are transmitted, but are maintained private, for example by transmitting signatures in a secure way. This is no longer required by amended claim 1 according to this request. On the other hand, amended claim 1 encompasses that signatures are not transmitted but are nevertheless made public, which is in contrast to claim 1 as granted.
The board therefore agrees with the opponent's argument that the features replaced by amendment not merely limit the scope of protection of claim 1, but - in contrast to the requirements set out in decision G 1/93 (see headnote 2 of the decision) - have a technical effect and contribute to the limitation of the scope of protection of claim 1. Those features therefore cannot be deleted from claim 1 without extending the scope of protection of claim 1 and thus infringing Article 123(3) EPC.



7.5 Claim 1 according to this request therefore does not fulfil the requirements of Article 123(3) EPC.
Proprietor's auxiliary requests 13 to 16



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Proprietor's auxiliary request 17


9. During oral proceedings the proprietor (appellant 1) submitted a further auxiliary request 17 in order to address the issue of Article 123(3) EPC.

9.1 In claim 1 of this request, step ii) of generating a first signature in claim 1 reads "said first correspondent A maintaining said first signature private to itself by avoiding transmission of said first signature". Likewise, step iv) of claim 1 has the corresponding formulation "said second correspondent B maintaining said second signature private to itself by avoiding transmission of said second signature".


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9.4 While the board agrees with the proprietor (appellant 1) that the amendment overcomes the objection under Article 123(3) EPC, the opponent (appellant 2) is correct that the amended features still give rise to an objection under Article 123(2) EPC.


9.5 For the reasons set out in point 5 above the board agrees with the opponent's argument that the act of keeping something private implies measures to keep the information secret, whereas not transmitting merely avoids such an activity without further measures regarding secrecy.


9.6 The board concurs with the opponent's arguments, in particular that the information alleged to be private is rather the random integer than the signature itself (see original application, page 5, lines 1 to 3). Keeping something private, i.e. secret, involves more than merely not transmitting such information. While there are several passages relating to different protocols directly and unambiguously disclosing that a transmission of the respective signatures SA and SB can be avoided (see point 5.3 above), there is however no direct and unambiguous disclosure for signatures SA and SB to be kept private.


9.7 Therefore the original application documents do not provide a direct and unambiguous disclosure for claim 1, step ii) comprising "said first correspondent A maintaining said first signature private to itself by avoiding transmission of said first signature" and step iv) with the corresponding formulation "said second correspondent B maintaining said second signature private to itself by avoiding transmission of said second signature".


9.8 Claim 1 according to this request therefore does not fulfil the requirements Article 123(2) EPC in contrast to the requirements of Article 100(c) EPC.


10. Hence, none of the proprietor's requests fulfils the requirements of the EPC.

Order

For these reasons it is decided that:
1. The decision under appeal is set aside.
2. The patent is revoked.

This decision T 108/12 (pdf) has European Case Law Identifier:    ECLI:EP:BA:2015:T010812.20150929. The file wrapper can be found here. Photo "Ancient Locked Door" by phaendin obtained via FreeDigitalPhotos.net.

4 comments :

  1. Someone ending up in the inescapable trap at least shows the trap to be inescapable. It would be very sad for an inescapable trap if people could always find ways to avoid it.

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  2. I thought for a while that divisional applications might be poisonous. Now there are as well lethal since they can end up in a trap, the moreover in an inescapable one!
    The problem with divisional is that often the applicant tries to obtain a broader scope of protection with respect to the parent application. The applicant then seeks a quick but more restricted protection with the parent and tries to "enlarge" with a divisional application. In the meantime, the applicant realised that his application could do more than originally thought of, and hence tries to push the border away. This strategy sometimes, as for example here, backfires.
    When one thinks what a divisional is meant to do, i.e. to give protection for parts of an original application which cannot be pursued in the original one, the attempts to get broader protection does not correspond to this aim. May be it would be good to come back to the basics of divisional applications......

    ReplyDelete
  3. I entirely agree with Raoul. Admittedly the EPC does not explicitely prohibit the filing of divisionals which are broader in scope than the parent application, but isn´t clear from the very designation "divisional" that something has to be cut out from the original application? Unfortunately the Boards seem quite reluctant to resort to the notion of abuse of the procedure. As a result divisionals are now widely used for tactical purposes, such as to overcome pending refusal of the parent application - not to speak of divisionals of divisionals.

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  4. "It may only be filed in respect of subject-matter which does not extend beyond the content of the earlier application as filed" (A.76)
    Yes, one may argue whether or not the system was meant for a two-step approach with getting quick, more restricted protection first, and then pursuing more extended protection through a divisional application. In that approach, one does not necessarily go beyond the limitations set by the application as originally filed. That is just as poisonous for a divisional application as for any application.

    ReplyDelete

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