T 1107/02 (Keypad processor/SCHLUMBERGER TECHNOLOGIES) of 27.10.2005

European Case Law Identifier: ECLI:EP:BA:2005:T110702.20051027
Date of decision: 27 October 2005
Case number: T 1107/02
Application number: 97400664.5
IPC class: G06F 1/00
H03M 11/00
Language of proceedings: EN
Distribution: C
Download and more information:
Decision text in EN (PDF, 63.493K)
Documentation of the appeal procedure can be found in the Register
Bibliographic information is available in: EN
Versions: Unpublished
Title of application: Apparatus and method to provide security for a keypad processor of a transaction terminal
Applicant name: Schlumberger Technologies, Inc.
Opponent name: -
Board: 3.5.01
Headnote: -
Relevant legal provisions:
European Patent Convention 1973 Art 56
Keywords: Inventive step (yes, after amendment)


Cited decisions:
Citing decisions:

Summary of Facts and Submissions

I. This appeal is against the decision of the examining division to refuse European patent application No. 97 400 664.5.

II. According to the decision under appeal, the subject-matter of all 34 claims before the examining division was obvious.

III. The examining division referred to the following prior art documents:

D1: DE-A-41 26 760

D2: EP-A-0 248 712

D3: US-A-4 926 173

D4: GB-A-2 190 775.

IV. On 6 May 2002 the notice and grounds of appeal were filed and the appeal fee was paid. The appellant requested that the decision be set aside and a patent be granted based on the claims on file.

V. By communication dated 18 April 2005 accompanying a summons to oral proceedings, the Board indicated that the subject-matter of claim 1 was not new.

VI. Oral proceedings were held on 27 October 2005. In the course of the hearing the appellant filed a new set of claims 1 to 25.

VII. Claims 1 and 16 read:

"1. A secured processor for use with a plurality of data entry ports which receive data signals, the secured processor comprising:

actual polling means operatively coupled to the plurality of data entry ports for conducting actual polling, the actual polling means providing an actual polling means signal and monitoring data entry ports to determine whether data signals are being received, the actual polling means identifying the data entry ports receiving data signals and generating an output signal corresponding thereto; and

false polling means operatively coupled to the plurality of data entry ports for providing a false polling means signal to the plurality of data entry ports for at least one of (i) producing a false indication that a data signal is being received by at least one of the plurality of data entry ports and (ii) producing a false indication that actual polling of the plurality of data entry ports is occurring;

wherein the actual polling means and the false polling means include signal generators for providing actual and false polling signals to the plurality of data entry ports in the form of pulsed signals, each pulse randomly varying in width."

"16. A method of providing a secured transmission of actual data signals received by a keypad of a transaction terminal to a processor which is external to the transaction terminal, the method comprising the steps of:

a) polling the keypad by generating at least one pulse signal to determine whether actual data signals are being provided thereto;

b) polling the keypad by generating at least one pulse signal to provide a false indication that at least one of (i) actual data signals are being provided thereto and (ii) actual polling of the transaction terminal is occurring; and

c) encoding the actual data signals and transmitting the encoded data signals to the external processor/,/

wherein the pulses randomly vary in width."

Independent claim 20 was directed to a transaction terminal comprising a secured processor circuit.

VIII. The appellant requested that the decision under appeal be set aside and a patent be granted on the basis of claims 1 to 25 filed at the oral proceedings.

IX. At the end of the oral proceedings the Board announced its decision.

Reasons for the Decision

1. Admissibility of the appeal

The appeal meets the requirements referred to in Rule 65(1) EPC and is, therefore, admissible.

2. Amendments

The main amendment to the three independent claims is the addition of the feature that the pulses of the actual and false polling means signals vary randomly in width. This feature was included in claims 13, 21 and 22 of the application as originally filed, referred to at various places in the description, and illustrated in figure 2C (box 63) and figure 2D (boxes 100,102). Thus, there is no objection against these claims under Article 123(2) EPC.

3. Clarity, support

The independent claims are regarded as fulfilling the requirements of Article 84 EPC (but see paragraph 8 below with respect to Rule 29(7) EPC).

4. The invention

As explained in the description of the present patent application (columns 1 and 2), transaction terminals are known which require a user to enter a personal identification number (PIN) via a keypad. Such terminals have the disadvantage that it is possible for an electronic eavesdropper to attach electrical tapping connections to the keypad conductors in order to monitor when a circuit connection is made by a key depression (e.g., when PIN data is entered). It is therefore possible for the electronic eavesdropper to obtain PIN information from the transaction terminal and to use that data to execute a fraudulent transaction. A known solution to this problem is to use polling signals which serve not only to sample the keypad in order to detect key actuations ("actual polling") but also to mask the actual polling signals ("false polling"). The invention aims at further reducing the likelihood of successful electronic eavesdropping by varying the duration of the actual and false polling pulses in a random manner.

5. The prior art

According to D2, held to be the closest prior art document, actual polling signals applied in sequential order to the rows of a keyboard matrix are detected on a randomly selected column in a receiving mode. False polling signals are simultaneously applied to the other columns in order to produce false indications that data signals are being received on these columns. A false polling signal is also applied to the receiving column in case it is determined that no genuine signal is present. This signal is necessarily somewhat shorter than the others, a difference which could at most be detected with the aid of sophisticated equipment. In another mode (see figure 5, case dx) actual key interrogation is inhibited and false polling pulses of the same width are simultaneously applied to a line and to each of the columns so that key activation is simulated.

6. Novelty

Claim 16, which is the most general claim, now includes the feature that the pulses (of the actual and false polling signals) vary randomly in width. In the decision under appeal (point 6.4), the examining division cited passages in D1 (column 2, lines 5 to 11), D3 (column 3, lines 18 to 28; column 6, lines 14 to 19) and D4 (page 2, lines 26 to 30) to demonstrate that in particular length modifications of polling signal pulse were known. However, in D1 and D4 it is apparently the simulated key actuations whose duration varies, not the individual polling pulses. Moreover, in D1 the variation is between devices rather than between pulses. In D3 a pulse pattern varies but not the pulse length. The Board further notes that in D2 the period of the false polling pulses can assume two (slightly) different values, which is not the same thing as a pulse having a randomly varying width.

It follows that the invention as set out in claim 16 is new (Article 54 EPC). The same applies to claims 1 and 20.

7. Inventive step

7.1 The purpose of varying the pulse width of the actual and false polling signals is to confuse an eavesdropper, who will not be able to detect a sampling pattern based on the pulse width, the pulses assuming a noise character (cf. column 6, lines 1 to 6; column 10, line 58 to column 11, line 5; column 13, lines 42 to 50). Starting out from D2, the technical problem can be seen in modifying the known circuit in a way which makes eavesdropping even more difficult.

7.2 The examining division, citing the passages from D1, D3 and D4 identified in paragraph 6 above, held that modifications of orders, forms, lengths and frequencies of the polling signals were measures familiar to the skilled person. The Board agrees that it is generally known in this technical area to generate various kinds of random signals in order to confuse eavesdroppers. It is for example pointed out in D2 that it is advantageous if the controlling microcomputer operates in as random a fashion as possible (column 8, lines 25 to 27). The invention is however not just concerned with this general principle but with its particular application to the length of the polling pulses. The question is whether the skilled person, having regard to the relevant prior art, would have thought of using randomly varying polling pulses in order to obtain some advantage.

7.3 It is clear that false polling signals, to serve their purpose, should in principle be indistinguishable from the actual polling signals. According to the prior art documents, in so far as they at all specify the shape of the shapes, all polling pulses are made as identical as possible (D2, figure 5; D4, figure 2). D2 is especially clear in this respect. According to this document, after a key associated with a certain column-row combination has been explored and found not to be activated, a false polling signal is immediately generated in order to minimise the difference in duration between this signal and the other false polling pulses simultaneously applied to the other columns (paragraph bridging columns 6 and 7). Against this background it is difficult to see why the skilled person would have thought of using anything but identical pulses for the actual and false polling signals. Although D2 states that the processes should preferably be performed randomly, an important aim in this document is in fact to obtain identical pulses. This strongly suggests that the statement was insufficient to lead the skilled person to the present invention.

7.4 With the benefit of hindsight it may naturally be argued that the skilled person would have realised that random variations of the pulse width are at least as effective as perfect uniformity to ensure the anonymity of the pulses and that such variations offer the additional advantage of increased overall complexity of the signals. But this would be a mere allegation amounting to little more than an explanation of the present invention, and appears less convincing than the observations above directly based on the prior art.

7.5 Thus, the subject-matter of claim 16 involves an inventive step (Article 56 EPC). The same applies to claims 1 and 20.

8. Remittal

The patent application must still be examined with respect to the other requirements of the Convention. It is for example noted that the claims do not contain reference signs (Rule 29(7) EPC) and that the description has not yet been adapted to the new claims. This final examination is left to the examining division.


For these reasons it is decided that:

1. The decision under appeal is set aside.

2. The case is remitted to the department of first instance for further prosecution.

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