Patent Description:
United States patent, publication number <CIT> discloses a method and apparatus to detect circuit tampering. The circuit includes a capacitor formed with the dielectric including the dielectric encasing elements of the circuit. The detector detects changes in the capacitance of the capacitor.

Embodiments of an active shielding device and method for active shielding are disclosed. The invention is defined in active shielding device claim <NUM> and a method for active shielding in claim <NUM>.

According to a first aspect of the invention, there is provided an active shielding device according to claim <NUM>.

The active shielding device includes current sources configured to generate currents, an analog wire shield unit connected to the current sources, a current to voltage converter connected to the analog wire shield unit and configured to generate a voltage in response to the currents that are generated by the current sources, and a voltage comparator connected to the current to voltage converter and configured to compare the voltage that is generated by the current to voltage converters with a reference voltage.

In an embodiment, the current sources are connected in parallel to each other.

The analog wire shield unit comprises analog wire windings that are connected between the current sources and the current to voltage converter.

In an embodiment, each of the analog wire windings is connected to a different current source of the current source.

In an embodiment, the active shielding device further includes switches connected between the current sources and the analog wire shield unit.

In an embodiment, the active shielding device further includes a controller configured to generate control signals to control the switches or the current to voltage converter.

In an embodiment, the controller includes a random number generator.

In an embodiment, the active shielding device further includes a second set of current sources configured to generate a second set of currents, a second current to voltage converter connected to the analog wire shield unit and configured to generate a second voltage in response to the second set of currents that are generated by the second set of current sources, and a second voltage comparator connected to the second current to voltage converter and configured to compare the second voltage with a second set of reference voltages.

In an embodiment, the active shielding device further includes a third voltage comparator configured to compare results from the voltage comparator and from the second voltage comparator.

In an embodiment, the active shielding device further includes a first set of switches connected between the current sources and the analog wire shield unit and a second set of switches connected between the second set of current sources and the analog wire shield unit.

In an embodiment, the active shielding device further includes a controller configured to generate control signals to control the first and second sets of switches.

According to a second aspect of the present invention, there is provided a method, a method for active shielding as defined in claim <NUM>. The method involves generating currents using an active shielding device, conducting the currents through analog wire windings of the active shielding device, generating a voltage in response to the currents using a current to voltage converter of the active shielding device, and comparing the voltage with a reference voltage using a voltage comparator of the active shielding device.

Other aspects in accordance with the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrated by way of example of the principles of the invention.

The present invention may be embodied in other specific forms. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by this detailed description. All changes which come within the meaning of the claims are to be embraced within their scope.

<FIG> depicts an active shielding device <NUM> in accordance with an embodiment of the invention. In the embodiment depicted in <FIG>, the active shielding device includes multiple current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, where N is an integer that is greater than one, an analog wire shield unit <NUM> connected to the current sources, a current to voltage converter <NUM> connected to the analog wire shield unit, and a voltage comparator <NUM> connected to the current to voltage converter. The active shielding device is used to protect a circuit to be protected <NUM>, which can be a cryptographic circuit, a security circuit, or other circuit, which can be connected to electrical wires or cables within the analog wire shield unit, electrical wires or cables between the current sources and the analog wire shield unit, or electrical wires or cables between the analog wire shield unit and the current to voltage converter. The active shielding device can be used in various applications, such as automotive applications, communications applications, industrial applications, medical applications, computer applications, and/or consumer or appliance applications. Although the illustrated active shielding device <NUM> is shown with certain components and described with certain functionality herein, other embodiments of the active shielding device may include fewer or more components to implement the same, less, or more functionality. For example, the active shielding device may include more than one analog wire shield unit. In another example, in some embodiments, the active shielding device may include more than one current to voltage converter and more than one voltage comparator. In yet another example, although the current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N are shown in <FIG> as being part of the active shielding device, in some embodiments, the current sources are external to the active shielding device and are not components of the active shielding device. In some embodiments, the active shielding device is an active shielding circuit. Components of the active shielding circuit may be implemented on a single substrate (e.g., integrated into the same IC chip) or distributed on multiple substrates (e.g., implemented on multiple IC chips). For example, at least one of the current sources, the analog wire shield unit, the current to voltage converter, and the voltage comparator is implemented on a single substrate (e.g., integrated into one IC chip) or distributed on multiple substrates (e.g., implemented on multiple IC chips). In some embodiments, the active shielding device and the circuit to be protected are integrated into the same IC chip.

Compared to an active shielding device that relies solely on digital shielding, the active shielding device <NUM> depicted in <FIG> implements analog active shielding that can be used independent from digital active shielding or in combination with digital active shielding. In the embodiment depicted in <FIG>, the active shielding device uses multiple current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N and the analog wire shield unit <NUM> for active shielding. Performance of active shielding in current domain is better than active shielding in voltage domain due to less noise injection. Current values from the analog current sources can be generated randomly, in form of a known pattern, or a combination of them. In addition, digital probing or applying <NUM>/<NUM> to the analog wire shield unit can be detected easily. For example, any invasive attack that cuts one or more electrical wires or cables within the analog wire shield unit <NUM> or applies <NUM>/<NUM> to one or more electrical wires or cables within the analog wire shield unit affects one or more currents that are generated by the current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, and changes the voltage range.

In the embodiment depicted in <FIG>, the current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N are configured to generate multiple currents, I<NUM>, I<NUM>,. The current sources can be implemented using various types of current sources that are known in the art. In some embodiments, the currents generated by the current sources are different from each other (i.e., each current source generates a unique current). In other embodiments, at least two of the currents, I<NUM>, I<NUM>,. , IN, generated by the current sources are identical to each other. In the embodiment depicted in <FIG>, the current sources are connected in parallel to each other such that each of the currents, I<NUM>, I<NUM>,. , IN, flows through the analog wire shield unit <NUM> in parallel. In some embodiments, the current sources are connected to positive voltages, which may be identical with each other or different from each other.

In the embodiment depicted in <FIG>, the analog wire shield unit <NUM> is connected between the current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N and the current to voltage converter <NUM>. The analog wire shield unit includes electrical cables or wires, which are made of conductive materials (e.g., metals). The analog wire shield unit includes multiple analog wire windings that are connected between the current sources and the current to voltage converter. In these embodiments, each of the current sources is connected to a different analog wire winding of the analog wire windings.

<FIG> depicts an analog wire shield unit <NUM>, which is an embodiment of the analog wire shield unit <NUM> depicted in <FIG>. However, the analog wire shield unit <NUM> depicted in <FIG> is not limited to the embodiment shown in <FIG>. In the embodiment depicted in <FIG>, the analog wire shield unit <NUM> includes multiple analog wire windings <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N that are connected to the current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N and to the current to voltage converter <NUM>. In the analog wire shield unit, each of the analog wire windings is connected to a different current source. For example, currents, I<NUM>, is conducted through the analog wire winding <NUM>-<NUM> to the current to voltage converter, currents, I<NUM>, is conducted through the analog wire winding <NUM>-<NUM> to the current to voltage converter, and currents, IN, is conducted through the analog wire winding <NUM>-N to the current to voltage converter. In some embodiments, at least one of the analog wire windings <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N is implemented on a topmost layer or topmost layers of an IC chip into which the active shielding device <NUM> is packaged. Security routing may be implemented on metal layers to minimal pitch and Arithmetic logic unit (Alu) width. In some embodiments, unused channels and/or spaces are filled to produce a shielded layout, which can thwart optical inspection and/or probing. In some embodiments, randomized routing is used in parallel and multi-layer interconnection is combined with a high metal density, which makes it more difficult for an attacker to get access to the relevant information in lower metal layers. In some embodiments, lower metals layers are used for signal lines and supply lines, which are not visible or accessible via pin connections. In some embodiments, lower metal layers are used for analog blocks with exception of ground and supply lines. Although the illustrated analog wire shield unit is shown with certain components and described with certain functionality herein, other embodiments of the analog wire shield unit may include fewer or more components to implement the same, less, or more functionality. For example, the analog wire shield unit may include more analog wire windings or less analog wire windings as shown in <FIG>. In another example, although the analog wire windings <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N are shown in <FIG> as having wire windings in certain form or style, in other embodiments, at least one of the analog wire windings <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N may have a wire winding in a form or style that is different from the form or style shown in <FIG>.

Turning back to <FIG>, the current to voltage converter <NUM> of the active shielding device <NUM> is configured to generate at least one voltage in response to the currents, I<NUM>, I<NUM>,. , IN, that are generated by the current sources <NUM>-<NUM>, <NUM>-<NUM>,. In some embodiments, the current to voltage converter is configured to generate a voltage that is proportional to the currents, I<NUM>, I<NUM>,. , IN, or a sum of the currents, I<NUM>, I<NUM>,.

<FIG> depicts a current to voltage converter <NUM>, which is an embodiment of the current to voltage converter <NUM> depicted in <FIG>. However, the current to voltage converter <NUM> depicted in <FIG> is not limited to the embodiment shown in <FIG>. In the embodiment depicted in <FIG>, the current to voltage converter <NUM> includes a resistor <NUM> and an amplifier <NUM>. In some embodiments, the amplifier is an operational amplifier (op-amp). In the embodiment depicted in <FIG>, the resistor has a fixed resistance value, "R. " However, in other embodiments, the resistor may have a variable resistance value. In an example of the operation of the current to voltage converter <NUM>, the amplifier and the resistor receive the currents, I<NUM>, I<NUM>,. , IN that are generated by the current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N of the active shielding device <NUM> depicted in <FIG> and generates an output voltage, "VOUT," which may be proportional to the sum of the currents, I<NUM>, I<NUM>,. In an embodiment, the output voltage, VOUT, can be expressed as: <MAT> Although the illustrated current to voltage converter is shown with certain components and described with certain functionality herein, other embodiments of the current to voltage converter may include fewer or more components to implement the same, less, or more functionality. For example, the current to voltage converter may include more than one amplifier and/or resistor or use different schemes/designs.

Turning back to <FIG>, the voltage comparator <NUM> of the active shielding device <NUM> is configured to compare at least one voltage that is generated by the current to voltage converter <NUM> with at least one reference voltage. In some embodiments, the voltage comparator is configured to compare a voltage that is generated by the current to voltage converter <NUM> with multiple reference voltages. Based on the comparison result between the voltage that is generated by the current to voltage converter and the at least one reference voltage, it can be determined whether or not the electrical cables or wires within the analog wire shield unit <NUM> are tampered with (e.g., voltage probing that involves cutting into the electrical cables or wires within the analog wire shield unit or altering at least one voltage or current in the electrical cables or wires within the analog wire shield unit. In some embodiments, if the voltage that is generated by the current to voltage converter is identical with the at least one reference voltage or within a threshold (e.g., ±<NUM>%) to the at least one reference voltage, it is determined that the electrical cables or wires within the analog wire shield unit are not tampered with. In these embodiments, if the voltage that is generated by the current to voltage converter is different from the at least one reference voltage or not within a threshold (e.g., ±<NUM>%) to the at least one reference voltage, it is determined that the electrical cables or wires within the analog wire shield unit are tampered with. In some embodiments, the active shielding device includes a controller that is configured to determine whether or not the electrical cables or wires within the analog wire shield unit are tampered with. The controller may be implemented in hardware (e.g., circuit or circuits), software, firmware, or a combination thereof. In an embodiment, the controller is implemented using a processor, such as a microcontroller, a host processor, a host, a digital signal processor (DSP), or a central processing unit (CPU). In some embodiments, the controller is configured to shut down or disable the circuit to be protected <NUM> if the electrical cables or wires within the analog wire shield unit are tampered with.

<FIG> depicts a voltage comparator <NUM>, which is an embodiment of the voltage comparator <NUM> depicted in <FIG>. However, the voltage comparator <NUM> depicted in <FIG> is not limited to the embodiment shown in <FIG>. In the embodiment depicted in <FIG>, the voltage comparator <NUM> includes two voltage comparison circuits <NUM>-<NUM>, <NUM>-<NUM>. In an example of the operation of the voltage comparator, the voltage comparison circuit <NUM>-<NUM> compares the output voltage, VOUT, from the current to voltage converter <NUM> with a reference voltage, Vref+A, while the voltage comparison circuit <NUM>-<NUM> compares the output voltage, VOUT, from the current to voltage converter with a reference voltage, Vref-Δ. A result signal is generated based on the comparison results of the voltage comparison circuits <NUM>-<NUM>, <NUM>-<NUM>. Although the illustrated voltage comparator is shown with certain components and described with certain functionality herein, other embodiments of the voltage comparator may include fewer or more components to implement the same, less, or more functionality. For example, the voltage comparator may include a single voltage comparison circuit or more than two voltage comparison circuit for different degree of voltage comparison precision.

In some embodiments, one or more switches are used to select one or more of the current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N to apply to the analog wire shield unit <NUM>. Consequently, voltages on the analog wire shield unit may vary, depending upon how many current source(s) or which of the current sources is/are selected, which makes it more difficult for an attacker to access information by probing a voltage of the analog wire shield unit. <FIG> depicts an active shielding device <NUM> that includes multiple switches <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N to control multiple current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N in accordance with an embodiment of the invention. In the embodiment depicted in <FIG>, the active shielding device includes the current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, an analog wire shield unit <NUM> connected to the current sources, a current to voltage converter <NUM> connected to the analog wire shield unit, a voltage comparator <NUM> connected to the current to voltage converter, the switches <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, and an optional controller <NUM>. The current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, the analog wire shield unit <NUM>, the current to voltage converter <NUM>, and the voltage comparator <NUM> in the embodiment depicted in <FIG> are the same as or similar to the current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, the analog wire shield unit <NUM>, the current to voltage converter <NUM>, and the voltage comparator <NUM> in the embodiment depicted in <FIG>, respectively. Although the illustrated active shielding device <NUM> is shown with certain components and described with certain functionality herein, other embodiments of the active shielding device may include fewer or more components to implement the same, less, or more functionality. For example, the active shielding device may include more than one analog wire shield unit. In another example, in some embodiments, the active shielding device may include more than one current to voltage converter and more than one voltage comparator. The active shielding device can operate in a first operational mode in which the active shielding device uses random data or known sequence to drive values on electrical cables or wires between the current sources and the current to voltage converter and subsequently check the results from the voltage comparator. The active shielding device can also operate in a second operational mode that allows for a specific value to be written to the active shielding device and a result be read back, which allows the active shielding device to be used as part of a secret that fails when the active shielding device is broken.

In the embodiment depicted in <FIG>, the current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N are configured to generate multiple currents, I<NUM>, I<NUM>,. The current sources can be implemented using various types of current sources that are known in the art. In some embodiments, the currents generated by the current sources are different from each other (i.e., each current source generates a unique current). In other embodiments, at least two of the currents, I<NUM>, I<NUM>,. , IN, generated by the current sources are identical to each other. In the embodiment depicted in <FIG>, the current sources are connected in parallel to each other such that each of the currents, I<NUM>, I<NUM>,. , IN, flows through the analog wire shield unit <NUM> in parallel. In the embodiment depicted in <FIG>, the analog wire shield unit <NUM> is connected between the current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N and the current to voltage converter <NUM>. The analog wire shield unit may include one or more electrical cables or wires, which are made of conductive materials (e.g., metals). In some embodiments, the analog wire shield unit includes multiple analog wire windings that are connected between the current sources and the current to voltage converter. In these embodiments, each of the current sources is connected to a different analog wire winding of the analog wire windings.

In the embodiment depicted in <FIG>, the current to voltage converter <NUM> is configured to generate at least one voltage in response to the currents, I<NUM>, I<NUM>,. , IN, that are generated by the current sources <NUM>-<NUM>, <NUM>-<NUM>,. In some embodiments, the current to voltage converter is configured to generate a voltage that is proportional to the currents, I<NUM>, I<NUM>,. , IN, or a sum of the currents, I<NUM>, I<NUM>,.

In the embodiment depicted in <FIG>, the voltage comparator <NUM> is configured to compare at least one voltage that is generated by the current to voltage converter <NUM> with at least one reference voltage. In some embodiments, the voltage comparator is configured to compare a voltage that is generated by the current to voltage converter <NUM> with multiple reference voltages. Based on the comparison result between the voltage that is generated by the current to voltage converter and the at least one reference voltage, it can be determined whether or not the electrical cables or wires within the analog wire shield unit <NUM> are tampered with (e.g., voltage probing that involves cutting into the electrical cables or wires within the analog wire shield unit or altering at least one voltage or current in the electrical cables or wires within the analog wire shield unit. In some embodiments, if the voltage that is generated by the current to voltage converter is identical with the at least one reference voltage or within a threshold (e.g., ±<NUM>%) to the at least one reference voltage, it is determined that the electrical cables or wires within the analog wire shield unit are not tampered with. In these embodiments, if the voltage that is generated by the current to voltage converter is different from the at least one reference voltage or not within a threshold (e.g., ±<NUM>%) to the at least one reference voltage, it is determined that the electrical cables or wires within the analog wire shield unit are tampered with.

In the embodiment depicted in <FIG>, the switches <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N are connected between the current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N and the analog wire shield unit <NUM> and are configured to select one or more of the current sources to apply to the analog wire shield unit, based on control signals, D<NUM>, D<NUM>,. In the embodiment depicted in <FIG>, the controller <NUM> is configured to generate control signals, D<NUM>, D<NUM>,. , DN to control the switches <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N and/or the current to voltage converter <NUM>. By controlling the switches and/or the current to voltage converter, voltages on the analog wire shield unit can vary (e.g., depending upon how many current source(s) or which of the current sources is/are selected), which makes it difficult for an attacker to access information by probing a voltage of the analog wire shield unit. The controller may be implemented in hardware (e.g., circuit or circuits), software, firmware, or a combination thereof. In an embodiment, the controller is implemented using a processor, such as a microcontroller, a host processor, a host, a DSP, or a CPU. The control signals, D<NUM>, D<NUM>,. , DN may be digital signals, which can be random digital signals/sequences or pre-defined digital signals/sequences. In some embodiments, the controller includes a random number generator configured to generate random digital sequences. Although the controller is shown in <FIG> as being a component of the active shielding device <NUM>, in other embodiments, the controller is external to the active shielding device. In some embodiments, the controller is configured to determine whether or not the electrical cables or wires within the analog wire shield unit are tampered with. In some embodiments, the controller is configured to shut down or disable a circuit to be protected, which can be connected to electrical wires or cables within the analog wire shield unit, electrical wires or cables between the current sources and the analog wire shield unit, or electrical wires or cables between the analog wire shield unit and the current to voltage converter, if the electrical cables or wires within the analog wire shield unit are tampered with. In some embodiments, digital active shielding can be combined with analog active shielding to provide more complex protection against invasive attacks. In some embodiments, one or more digital logic circuits are serially connected with an electrical cable or wire such that signals in the electrical cable or wire can be altered by the digital logic circuits. For example, voltages on the electrical cable or wire may vary, depending upon the place or section at which the electrical cable or wire is probed, which makes it more difficult for an attacker to access information by probing the voltage at the electrical cable or wire.

In some embodiments, multiple sets of current sources, current to voltage converters, and voltage comparators are used with an analog wire shield unit. Consequently, voltages on the analog wire shield unit may be verified or validated repetitively, which makes it more difficult for an attacker to access information by probing a voltage of the analog wire shield unit. <FIG> depicts an active shielding device <NUM> that includes multiple sets of current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, current to voltage converters <NUM>-<NUM>, <NUM>-<NUM>, and voltage comparators <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> in accordance with an embodiment of the invention. In the embodiment depicted in <FIG>, the active shielding device includes a first set of current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, a second set of current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, a third set of current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, and a fourth set of current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, an analog wire shield unit <NUM> connected to the current sources, first and second current to voltage converters <NUM>-<NUM>, <NUM>-<NUM> connected to the analog wire shield unit, first and second voltage comparators <NUM>-<NUM>, <NUM>-<NUM> connected to the current to voltage converters, and a third voltage comparator <NUM>-<NUM> connected to the first and second voltage comparators <NUM>-<NUM>, <NUM>-<NUM>. The current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, the analog wire shield unit <NUM>, the current to voltage converters <NUM>-<NUM>, <NUM>-<NUM>, and the voltage comparators <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> in the embodiment depicted in <FIG> are the same as or similar to the current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, the analog wire shield unit <NUM>, the current to voltage converter <NUM>, and the voltage comparator <NUM> in the embodiment depicted in <FIG>, respectively. Although the illustrated active shielding device <NUM> is shown with certain components and described with certain functionality herein, other embodiments of the active shielding device may include fewer or more components to implement the same, less, or more functionality. For example, the active shielding device may include more than one analog wire shield unit.

In the embodiment depicted in <FIG>, each of the first set of current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, the second set of current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, the third set of current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, and the fourth set of current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N is configured to generate multiple currents, I<NUM>, I<NUM>,. The current sources can be implemented using various types of current sources that are known in the art. In some embodiments, the currents generated by the current sources are different from each other (i.e., each current source generates a unique current). In other embodiments, at least two of the currents, I<NUM>, I<NUM>,. , IN, generated by the current sources are identical to each other. In the embodiment depicted in <FIG>, each current source within one of the first, second, third, and fourth sets of current sources is connected in parallel to each other such that each of the currents, I<NUM>, I<NUM>,. , IN, flows through the analog wire shield unit <NUM> in parallel.

In the embodiment depicted in <FIG>, the analog wire shield unit <NUM> is connected to the second set of current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, and to the fourth set of current sources <NUM>-<NUM>, <NUM>-<NUM>,. The analog wire shield unit may include one or more electrical cables or wires, which are made of conductive materials (e.g., metals). In some embodiments, the analog wire shield unit includes multiple analog wire windings that are connected between the second set of current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N or the fourth set of current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N and the current to voltage converters <NUM>-<NUM>, <NUM>-<NUM>. In these embodiments, each current source within the second set of current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N is connected to a different analog wire winding of the analog wire windings, and/or each current source within the fourth set of current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N is connected to a different analog wire winding of the analog wire windings.

In the embodiment depicted in <FIG>, the first current to voltage converter <NUM>-<NUM> is connected to the first set of current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N and to the fourth set of current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N through the analog wire shield unit <NUM>. The first current to voltage converter <NUM>-<NUM> is configured to generate a first output voltage, Vout1, in response to the currents, I<NUM>, I<NUM>,. , IN, that are generated by the first and fourth sets of current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. In some embodiments, the first output voltage, Vout1, is proportional to the currents, I<NUM>, I<NUM>,. , IN, or a sum of the currents, I<NUM>, I<NUM>,.

In the embodiment depicted in <FIG>, the first voltage comparator <NUM>-<NUM> is connected to the first current to voltage converter <NUM>-<NUM> and configured to compare the first output voltage, Vout1, with at least one reference voltage to generate a result signal, CMP1, which may be an analog signal or a digital signal. In some embodiments, the first voltage comparator includes multiple voltage comparison circuits configured to compare the first output voltage, Vout1, with multiple reference voltages.

In the embodiment depicted in <FIG>, the second current to voltage converter <NUM>-<NUM> is connected to the second set of current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N and to the third set of current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N through the analog wire shield unit <NUM>. The second current to voltage converter is configured to generate a second output voltage, Vout2, in response to the currents, I<NUM>, I<NUM>,. , IN, that are generated by the second and third sets of current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. In some embodiments, the second output voltage, Vout2, is proportional to the currents, I<NUM>, I<NUM>,. , IN, or a sum of the currents, I<NUM>, I<NUM>,.

In the embodiment depicted in <FIG>, the second voltage comparator <NUM>-<NUM> is connected to the second current to voltage converter <NUM>-<NUM> and configured to compare the second output voltage, Vout2, with at least one reference voltage to generate a result signal, CMP2, which may be an analog signal or a digital signal. In some embodiments, the first voltage comparator includes multiple voltage comparison circuits configured to compare the second output voltage, Vout1, with multiple reference voltages.

In the embodiment depicted in <FIG>, the third voltage comparator <NUM>-<NUM> is configured to compare the result signal, CMP1, from the first voltage comparator <NUM>-<NUM> and the result signal, CMP2, from the second voltage comparator <NUM>-<NUM> to generate a comparison result. Based on the comparison result from the third voltage comparator, it can be determined whether or not the electrical cables or wires within the analog wire shield unit <NUM> are tampered with (e.g., voltage probing that involves cutting into the electrical cables or wires within the analog wire shield unit or altering at least one voltage or current in the electrical cables or wires within the analog wire shield unit. In some embodiments, if the result signal, CMP1, from the first voltage comparator <NUM>-<NUM> is identical with the result signal, CMP2, from the second voltage comparator <NUM>-<NUM> or within a threshold (e.g., ±<NUM>%) to the result signal, CMP2, from the second voltage comparator <NUM>-<NUM>, it is determined that the electrical cables or wires within the analog wire shield unit are not tampered with. In these embodiments, if the result signal, CMP1, from the first voltage comparator <NUM>-<NUM> is different from the result signal, CMP2, from the second voltage comparator <NUM>-<NUM> or not within a threshold (e.g., ±<NUM>%) to the result signal, CMP2, from the second voltage comparator <NUM>-<NUM>, it is determined that the electrical cables or wires within the analog wire shield unit are tampered with. In some embodiments, the active shielding device includes a controller that is configured to determine whether or not the electrical cables or wires within the analog wire shield unit are tampered with. The controller may be implemented in hardware (e.g., circuit or circuits), software, firmware, or a combination thereof. In an embodiment, the controller is implemented using a processor, such as a microcontroller, a host processor, a host, a DSP, or a CPU. In some embodiments, the controller is configured to shut down or disable a circuit to be protected, which can be connected to electrical wires or cables within the analog wire shield unit, electrical wires or cables between the current sources and the analog wire shield unit, or electrical wires or cables between the analog wire shield unit and the current to voltage converters, if the electrical cables or wires within the analog wire shield unit are tampered with. In some embodiments, digital active shielding can be combined with analog active shielding to provide more complex protection against invasive attacks. In some embodiments, one or more digital logic circuits are serially connected with an electrical cable or wire such that signals in the electrical cable or wire can be altered by the digital logic circuits. For example, voltages on the electrical cable or wire may vary, depending upon the place or section at which the electrical cable or wire is probed, which makes it more difficult for an attacker to access information by probing the voltage at the electrical cable or wire.

In some embodiments, one or more switches are used to select one or more of the current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N to apply to the analog wire shield unit <NUM>, the first current to voltage converter <NUM>-<NUM>, or the second current to voltage converter <NUM>-<NUM>. Consequently, voltages on the analog wire shield unit may vary, depending upon how many current source(s) or which of the current sources is/are selected, which makes it more difficult for an attacker to access information by probing a voltage of the analog wire shield unit. <FIG> depicts an active shielding device <NUM> that includes multiple switches <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N to control the current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N in accordance with an embodiment of the invention. In the embodiment depicted in <FIG>, the active shielding device includes the current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, the analog wire shield unit <NUM> connected to the current sources, the first and second current to voltage converters <NUM>-<NUM>, <NUM>-<NUM> connected to the analog wire shield unit, the first and second voltage comparators <NUM>-<NUM>, <NUM>-<NUM> connected to the current to voltage converters, the third voltage comparator <NUM>-<NUM> connected to the first and second voltage comparators <NUM>-<NUM>, <NUM>-<NUM>, the switches <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, and an optional controller <NUM>. The switches <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N and the controller <NUM> in the embodiment depicted in <FIG> are the same as or similar to the switches <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N and the controller <NUM> in the embodiment depicted in <FIG>, respectively. Although the illustrated active shielding device <NUM> is shown with certain components and described with certain functionality herein, other embodiments of the active shielding device may include fewer or more components to implement the same, less, or more functionality. For example, the active shielding device may include more than one analog wire shield unit.

In the embodiment depicted in <FIG>, the switches <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N are configured to select one or more of the current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N to apply to the analog wire shield unit <NUM>, the first current to voltage converter <NUM>-<NUM>, or the second current to voltage converter <NUM>-<NUM>, based on control signals, D<NUM>, D<NUM>,. In the embodiment depicted in <FIG>, the controller <NUM> is configured to generate control signals, D<NUM>, D<NUM>,. , DN to control the switches <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N and/or at least one of the first and second current to voltage converters <NUM>-<NUM>, <NUM>-<NUM>. By controlling the switches and/or the current to voltage converters, voltages on the analog wire shield unit can vary (e.g., depending upon how many current source(s) or which of the current sources is/are selected), which makes it difficult for an attacker to access information by probing a voltage of the analog wire shield unit. The controller may be implemented in hardware (e.g., circuit or circuits), software, firmware, or a combination thereof. In an embodiment, the controller is implemented using a processor, such as a microcontroller, a host processor, a host, a DSP, or a CPU. The control signals, D<NUM>, D<NUM>,. , DN may be digital signals, which can be random digital signals/sequences or pre-defined digital signals/sequences. In some embodiments, the controller includes a random number generator configured to generate random digital sequences. Although the controller is shown in <FIG> as being a component of the active shielding device <NUM>, in other embodiments, the controller is external to the active shielding device. In some embodiments, the controller is configured to shut down or disable a circuit to be protected, which can be connected to electrical wires or cables within the analog wire shield unit, electrical wires or cables between the current sources and the analog wire shield unit, or electrical wires or cables between the analog wire shield unit and the current to voltage converters <NUM>-<NUM>, <NUM>-<NUM>, if the electrical cables or wires within the analog wire shield unit are tampered with.

Digital active shielding can be combined with analog active shielding to provide more complex protection against invasive attacks. In some embodiments, one or more digital logic circuits are serially connected with an electrical cable or wire such that signals in the electrical cable or wire can be altered by the digital logic circuits. For example, even number (e.g., <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) of inverters can be serially connected with an electrical cable or wire such that when a digital signal flows through these inverters, the output signal of the even number of inverters is identical with the original signal. However, when an attacker probes the electrical cable or wire, the probed voltage may not correspond to the original digital signal. For example, when an attacker probes the electrical cable or wire after an odd number of inverters, the probed voltage corresponds to an inverted version of the original digital signal. However, when an attacker probes the electrical cable or wire after an even number of inverters, the probed voltage corresponds to the original digital signal. Consequently, voltages on the electrical cable or wire may vary, depending upon the place or section at which the electrical cable or wire is probed, which makes it more difficult for an attacker to access information by probing the voltage at the electrical cable or wire.

<FIG> depicts an active shielding device <NUM> that includes a combination of a digital shielding unit <NUM> and the analog wire shield unit <NUM> in accordance with an embodiment of the invention. In the embodiment depicted in <FIG>, the active shielding device includes the current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, the analog wire shield unit <NUM> connected to the current sources, the first and second current to voltage converters <NUM>-<NUM>, <NUM>-<NUM> connected to the analog wire shield unit, the first and second voltage comparators <NUM>-<NUM>, <NUM>-<NUM> connected to the current to voltage converters, the third voltage comparator <NUM>-<NUM> connected to the first and second voltage comparators <NUM>-<NUM>, <NUM>-<NUM>, the switches <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, an optional controller <NUM>, the digital shielding unit <NUM> connected to the current sources, two digital logics <NUM>-<NUM>, <NUM>-<NUM>, and a digital comparator <NUM>. The switches <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N and the controller <NUM> in the embodiment depicted in <FIG> are the same as or similar to the switches <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N and the controller <NUM> in the embodiment depicted in <FIG>, respectively. Although the illustrated active shielding device <NUM> is shown with certain components and described with certain functionality herein, other embodiments of the active shielding device may include fewer or more components to implement the same, less, or more functionality. For example, the active shielding device may include more than one digital shielding unit and/or more than one analog wire shield unit.

In the embodiment depicted in <FIG>, the digital shielding unit <NUM> is connected between the second set of current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, and to the third set of current sources <NUM>-<NUM>, <NUM>-<NUM>,. In the embodiment depicted in <FIG>, the digital shielding unit includes a first set of inverters <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-K, where K is a positive even integer, which is connected between the second set of current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, and to the third set of current sources <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>, and a second set of inverters <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-K, which is connected between the digital logic <NUM>-<NUM> and the digital comparator <NUM>. The digital shielding unit may include one or more electrical cables or wires, which are made of conductive materials (e.g., metals). In some embodiments, the electrical cables or wires within the digital shielding unit is located to the top metal layer of the digital shielding unit <NUM>. When an attacker probes the electrical cables or wires, the probed voltage may not correspond to the original digital signal. For example, when an attacker probes the electrical cable or wire after an odd number of inverters, the probed voltage corresponds to an inverted version of the original digital signal. However, when an attacker probes the electrical cable or wire after an even number of inverters, the probed voltage corresponds to the original digital signal. Consequently, voltages on the electrical cable or wire may vary, depending upon the place or section at which the electrical cable or wire is probed, which makes it more difficult for an attacker to access information by probing the voltage at the electrical cable or wire. Although the illustrated the digital shielding unit <NUM> is shown with certain components and described with certain functionality herein, other embodiments of the digital shielding unit may include fewer or more components to implement the same, less, or more functionality. For example, the digital shielding unit may include only one set of even number of inverters.

In the embodiment depicted in <FIG>, the controller <NUM> is configured to generate digital control signals, D<NUM>, D<NUM>,. , DM, where M is a positive integer that is greater than one, which may be random digital signals/sequences or pre-defined digital signals/sequences. The controller may be implemented in hardware (e.g., circuit or circuits), software, firmware, or a combination thereof. In an embodiment, the controller is implemented using a processor, such as a microcontroller, a host processor, a host, a DSP, or a CPU. In some embodiments, the controller includes a random number generator configured to generate random digital sequences. The control signals, D<NUM>, D<NUM>,. , DN, where N is an integer that is smaller than M, to control the switches <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N, <NUM>-<NUM>, <NUM>-<NUM>,. By controlling the switches, voltages on the analog wire shield unit <NUM> can vary (e.g., depending upon how many current source(s) or which of the current sources is/are selected), which makes it difficult for an attacker to access information by probing a voltage of the analog wire shield unit. Although the controller is shown in <FIG> as being a component of the active shielding device <NUM>, in other embodiments, the controller is external to the active shielding device. In some embodiments, the controller is configured to shut down or disable a circuit to be protected, which can be connected to electrical wires or cables within the analog wire shield unit, electrical wires or cables between the current sources and the analog wire shield unit, or electrical wires or cables between the current to voltage converters <NUM>-<NUM>, <NUM>-<NUM> and the analog wire shield unit, if the electrical cables or wires within the analog wire shield unit are tampered with.

In the embodiment depicted in <FIG>, the digital logic <NUM>-<NUM> is configured to generate a result signal, OUTi, based on the digital signals, D<NUM>, D<NUM>,. The digital logic <NUM>-<NUM> is configured to generate a result signal, OUTo, based on the digital signals, D<NUM>, D<NUM>,. The digital logics <NUM>-<NUM>, <NUM>-<NUM> are identical digital circuits and/or configured to perform identical functions. In some embodiments, the digital logics are digital gates such as NAND gates, OR gates or XOR gates, or more complex digital logics. The digital comparator <NUM> is configured to compare the result signal, OUTi, from the digital logic <NUM>-<NUM> with the result, OUTo, from the digital logic <NUM>-<NUM> to generate a digital comparison result. Based on the digital comparison result from the digital comparator, it can be determined whether or not the electrical cables or wires within the digital shielding unit <NUM> are tampered with (e.g., voltage probing that involves cutting into the electrical cables or wires within the digital shielding unit or altering at least one voltage or current in the electrical cables or wires within the digital shielding unit. In some embodiments, if the result signal, OUTi, from the digital logic <NUM>-<NUM> is identical with the result, OUTo, from the digital logic <NUM>-<NUM>, it is determined that the electrical cables or wires within the digital shielding unit are not tampered with. In these embodiments, if the result signal, OUTi, from the digital logic <NUM>-<NUM> is different from the result, OUTo, from the digital logic <NUM>-<NUM>, it is determined that the electrical cables or wires within the digital shielding unit are tampered with. In some embodiments, the active shielding device includes a controller (e.g., the controller <NUM>) that is configured to determine whether or not the electrical cables or wires within the digital shielding unit are tampered with. The controller may be implemented in hardware (e.g., circuit or circuits), software, firmware, or a combination thereof. In an embodiment, the controller is implemented using a processor, such as a microcontroller, a host processor, a host, a DSP, or a CPU. In some embodiments, the controller is configured to shut down or disable a circuit to be protected, which can be connected to electrical wires or cables within the digital shielding unit, electrical wires or cables between the current sources and the digital shielding unit, or electrical wires or cables between the digital shielding unit and the digital comparator, if the electrical cables or wires within the digital shielding unit are tampered with.

<FIG> is a process flow diagram of a method for active shielding in accordance to an embodiment of the invention. According to the method, at block <NUM>, currents are generated using an active shielding device. At block <NUM>, the currents are conducted through analog wire windings of the active shielding device. At block <NUM>, a voltage is generated in response to the currents using a current to voltage converter of the active shielding device. At block <NUM>, the voltage is compared with a reference voltage using a voltage comparator of the active shielding device. The active shielding device may be similar to, the same as, or a component of the active shielding device <NUM> depicted in <FIG>, the active shielding device <NUM> depicted in <FIG>, the active shielding device <NUM> depicted in <FIG>, and/or the active shielding device <NUM> depicted in <FIG>.

<FIG> is a process flow diagram of a method for active shielding in accordance to another embodiment of the invention. According to the method, at block <NUM>, currents are generated using an active shielding device. At block <NUM>, the currents are conducted through analog wire windings of the active shielding device in response to a digital control sequence. At block <NUM>, a voltage is generated in response to the currents using a current to voltage converter of the active shielding device. At block <NUM>, the voltage is compared with a reference voltage using a voltage comparator of the active shielding device. At block <NUM>, the digital control sequence is processed before conducting the digital control sequence through inverters of an active shielding unit of the active shielding device and after conducting the digital control sequence through the inverters using digital logics of the active shielding device to generate a first processing result signal and a second result signal, respectively. At black <NUM>, the first processing result signal is compared with the second result signal. The active shielding device may be similar to, the same as, or a component of the active shielding device <NUM> depicted in <FIG>.

It should also be noted that at least some of the operations for the methods described herein may be implemented using software instructions stored on a computer useable storage medium for execution by a computer. As an example, an embodiment of a computer program product includes a computer useable storage medium to store a computer readable program.

The computer-useable or computer-readable storage medium can be an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system (or apparatus or device). Examples of non-transitory computer-useable and computer-readable storage media include a semiconductor or solid-state memory, magnetic tape, a removable computer diskette, a random-access memory (RAM), a read-only memory (ROM), a rigid magnetic disk, and an optical disk. Current examples of optical disks include a compact disk with read only memory (CD-ROM), a compact disk with read/write (CD-R/W), and a digital video disk (DVD).

Alternatively, embodiments of the invention may be implemented entirely in hardware or in an implementation containing both hardware and software elements. In embodiments which use software, the software may include but is not limited to firmware, resident software, microcode, etc..

Claim 1:
An active shielding device (<NUM>) for integration into an integrated circuit, IC, chip, the active shield device comprising:
a plurality of current sources (<NUM>-<NUM>, <NUM>-<NUM>,...<NUM>-N configured to generate a plurality of currents (I<NUM>, I<NUM>,...IN);
an analog wire shield unit (<NUM>) connected to the current sources;
a current to voltage converter (<NUM>) connected to the analog wire shield unit and configured to generate a voltage in response to the currents that are generated by the current sources and flow through the analog wire shield unit,
wherein the analog wire shield unit comprises a plurality of analog wire windings (<NUM>-<NUM>, <NUM>-<NUM>... <NUM>-N) that are connected between the current sources and the current to voltage converter; and
a voltage comparator (<NUM>) connected to the current to voltage converter and configured to compare the voltage that is generated by the current to voltage converters with a reference voltage to determine whether the plurality of analog wire windings within the analog wire shield unit are tampered with.