Registers – Records – Conductive
Reexamination Certificate
1999-07-06
2001-08-21
Lee, Michael G. (Department: 2876)
Registers
Records
Conductive
C235S487000, C257S679000
Reexamination Certificate
active
06276609
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a data carrier provided with a circuit which is realized in integrated technology and includes two supply voltage source terminals which can deliver a supply voltage, and includes data processing means which are suitable for processing data while utilizing a characteristic value, are realized in hardware technology and include supply voltage drain terminals via which the supply voltage can be applied to circuit elements of the data processing means, and includes electrically conductive connection means for electrically conductively connecting the supply voltage source terminals to the supply voltage drain terminals, and in which the processing of data by means of the data processing means causes the occurrence of a current peak pattern on supply voltage drain terminals of the data processing means, the pattern configuration of the current peak pattern being dependent on the processed data and on the characteristic value.
The invention also relates to a circuit for a data carrier which is realized in integrated technology and includes two supply voltage source terminals which can deliver a supply voltage, and includes data processing means which are suitable for processing data while utilizing a characteristic value, are realized in hardware technology and include supply voltage drain terminals via which the supply voltage can be applied to circuit elements of the data processing means, and includes electrically conductive connection means for electrically conductively connecting the supply voltage source terminals to the supply voltage drain terminals, and in which the processing of data by means of the data processing means causes the occurrence of a current peak pattern on supply voltage drain terminals of the data processing means, the pattern configuration of the current peak pattern being dependent on the processed data and on the characteristic value.
RELATED ART
A data carrier of the kind set forth in the first paragraph and a circuit of the kind set forth in the second paragraph are commercially available and hence known. The data processing means in the known data carrier and the known circuit are formed by encryption/decryption means whereby data can be encrypted and decrypted. During the execution of an encryption or a decryption operation, a current peak pattern occurs on the supply voltage drain terminals of the encryption/decryption means. This current peak pattern is significant of the data processed in the encryption/decryption means, and significant of the characteristic value used in the encryption/decryption means, i.e. the secret key of these means. It is problematic in the known data carrier and the known circuit that the respective current peak patterns caused occur not only on the supply voltage drain terminals of the encryption/decryption means, but unfortunately also on the supply voltage source terminals of the circuit; consequently, these current peak patterns occur on the supply leads of the circuit, or the data carrier, leading to the supply voltage source terminals. Such occurrence of the respective current peak pattern caused on said supply leads can be used so as to apply given known data for processing to the data processing means an arbitrarily large number of times in succession, and to subject, during the processing of such known data, the invariably the same current peak patterns then produced to scrutinization or detection during which information can be extracted as regards the characteristic value used in the encryption/decryption means, i.e. the secret key, be it while applying intricate but known and available correlation methods or comparison methods and while utilizing the detected current peak patterns. Evidently, such cracking of a secret key is undesirable, because the desired secrecy can then no longer be very reliably guaranteed.
SUMMARY OF THE INVENTION
It is an object of the invention to avoid the described problems and to provide an improved data carrier or an improved circuit for a data carrier while using simple and only very few additional means.
In order to achieve the above objects a data carrier of the kind set forth in the first paragraph according to the invention is characterized in that additionally there are provided suppression means whereby an occurrence on the supply voltage source terminals of the current peak pattern occurring on supply voltage drain terminals of the data processing means can be suppressed.
In order to achieve the above objects, furthermore, a circuit of the kind set forth in the second paragraph according to the invention is characterized in that additionally there are provided suppression means whereby an occurrence on the supply voltage source terminals of the current peak pattern occurring on supply voltage drain terminals of the data processing means can be suppressed.
By taking the steps according to the invention, it is very simply, effectively and reliably ensured that the peak current patterns appearing on the supply voltage drain terminals of the data processing means due to the data processing by the data processing means still occur thereon, but no longer on the supply voltage source terminals of the circuit according to the invention for a data carrier according to the invention, or only in a rudimentary form which has been suppressed to such an extent that unauthorized and undesirable scrutinization or detection of current peak patterns while utilizing supply leads of a circuit according to the invention is no longer possible. The steps according to the invention thus ensure extremely reliably that no undesirable conclusions-can be drawn from current peak patterns, and that hence undesirable determination of characteristic values, such as a secret code, a secret key or a so-called hash value and the like, is impossible.
The suppression means may be formed by special data processing means. However, it has been found that it is particularly advantageous to take the steps disclosed in the claims
2
and
9
, because such an implementation features simplicity and reliability.
In the simplest case the filter means may be formed by the capacitor and connection segments of the connection means present between the supply voltage source terminals and the capacitor, the ohmic resistance of said connection segments being used as current limiting means which constitute, in conjunction with the capacitor, filter means exhibiting a low-pass behavior. However, it has been found to be even more advantageous to take the steps disclosed in the claims
3
and
10
, because the low-pass behavior of the filter means can then be readily adapted to different requirements. It has been found that it is particularly advantageous to take additionally, if necessary, the steps disclosed in the claims
4
and
11
.
It is to be noted that the use of a capacitor, which is connected to supply voltage terminals, for the data carrier disclosed in the first paragraph or the circuit disclosed in the second paragraph is known per se. In the known data carrier, or the known circuit, however, this capacitor constitutes a purely auxiliary capacitor which serves to bridge intervals occurring in the power supply. The capacitor in the data carrier according to the invention or the circuit according to the invention, however, forms a part of filter means which constitute suppression means for suppressing current peak patterns.
The capacitor, realized in integrated technology, may have, for example a strip-shaped or L-shaped or U-shaped construction. However, it has been found that it is particularly advantageous to take the steps disclosed in the claims
5
and
12
. Such a construction offers very effective attenuation of the current peaks occurring during the processing of data by means of the data processing means.
A construction in conformity with the claims
6
and
13
is also advantageous, because an as short as possible, and hence low-ohmic, realization is thus ensured for all connection segments between the two connection zones of the auxiliary capacitance and the su
Czar Bernhard
Eber Wolfgang
Thuringer Peter
Franklin Jamara A
Lee Michael G.
U.S. Philips Corporation
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