# Patent

## Title
Copy protection without non-volatile memory

## Abstract

An integrated circuit includes a fingerprint element and a decryption circuit. The fingerprint element generates a fingerprint, where the fingerprint is reproducible and represents an inherent manufacturing process characteristic unique to the integrated circuit device. The decryption circuit decrypts, using a decryption key that is based on the fingerprint, an encrypted data in order to extract data. In one embodiment, the propagation delay of various circuit elements are used to generate the fingerprint. In another embodiment, the specific frequency of an oscillator is used to generate the fingerprint. In yet another embodiment, a ratio of measurable values is used to generate the fingerprint. In another embodiment, differences in transistor threshold voltages are used to generate the fingerprint. In yet another embodiment, variations in line widths are used to generate the fingerprint.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation of U.S. Patent Application having the application Ser. No. 11/101,076, filed on Apr. 7, 2005, and entitled “Copy Protection Without Non-Volatile Memory” by Stephen M. Trimberger, which is a divisional of U.S. Patent Application having the application Ser. No. 09/765,907, filed on Jan. 19, 2001, which issued as U.S. Pat. No. 7,380,131, entitled “Copy Protection Without Non-Volatile Memory” by Stephen M. Trimberger.


FIELD OF THE INVENTION
An embodiment of the invention relates generally to an integrated circuit device such as a programmable logic device, and specifically to protecting circuit designs in an integrated circuit device.
BACKGROUND
Programmable logic devices (PLDs) are a well-known type of general purpose integrated circuit that may be programmed to implement one or more desired circuit designs. One type of PLD, a field programmable gate array (FPGA), typically includes an array of identical configurable logic blocks (CLBs) surrounded by input/output blocks (IOBs). Each CLB may be individually programmed to perform a variety of logic functions. A programmable interconnect selectively connects the CLBs to each other and to the various IOBs to implement complex logic functions and circuits.
To program the PLD to implement a circuit design, a user captures the circuit design using a well-known design capture tool, and then uses well-known software tools to convert the captured design into a device specific bitwise representation. The bitwise representation, commonly referred to as a configuration bitstream, is stored in a non-volatile storage device such as a Programmable Read Only Memory (PROM). Upon power-up, the non-volatile storage device transmits the configuration bitstream to the FPGA, where is loaded into a configuration memory array that controls various switches and multiplexers within the CLBs, IOBs, and programmable interconnect to implement the desired circuit design. Once configured, the FPGA implements the circuit design embodied in the configuration data. For a more detailed description of FPGA architecture, configuration, and operation, refer to The Xilinx 1998 Data Book entitled “The Programmable Logic Data Book”, Chapter 4, available from Xilinx, Inc., and incorporated herein by reference.
The FPGA's configuration memory array is typically a volatile memory such as Static Random Access Memory (SRAM). Thus, when the FPGA is powered off, the configuration data stored in its configuration memory array is lost. Consequently, when the FPGA is again powered up, it must be re-configured using configuration data provided by the non-volatile storage device, as described above.
The non-volatile storage device is typically external to the FPGA not only because of its size and cost but also because of the complexity of its manufacturing process. For example, the manufacturing process of a PROM requires several more masking and deposition steps than that of an SRAM, because while an SRAM uses cross-coupled transistors to store information, a PROM stores information using floating gate transistors, which require an additional layer of polysilicon. Because of the increased manufacturing complexity of non-volatile memory, as compared to volatile memory, the latest processing technology may be available for manufacturing volatile memory as much as a year or more before it is available for manufacturing non-volatile memory. Accordingly, providing the non-volatile memory external to the FPGA allows the FPGA to be manufactured using the latest manufacturing technology, which in turn provides a competitive advantage.
Because creation of the circuit design embodied in the configuration bitstream requires significant time and expense, it is desirable to protect the configuration data from illegal copying by competitors and unauthorized resellers. Unfortunately, the circuit design for an FPGA may be illegally copied by simply copying the configuration bitstream stored in the non-volatile memory. The copied bitstream may then be used to illegally configure other FPGAs, or may be reverse-engineered to extract the circuit design.
To protect against unauthorized copying, the configuration data may be encrypted before it is stored in the non-volatile memory, transmitted to the FPGA in encrypted form, and then decrypted in the FPGA. Thus, in order to copy the circuit design embodied in the configuration data, one must determine the decryption key, thereby making unauthorized copying difficult. However, because the configuration data must be decrypted each time it is received from the external memory during power-up, the FPGA must include a non-volatile memory to store the decryption key. As discussed above, it is not desirable to include non-volatile memory within the FPGA. Accordingly, there is a need for a method of protecting the configuration data when transmitted to the FPGA that does not require a non-volatile memory within the FPGA.
SUMMARY
An embodiment of a method to secure communication of data between an integrated circuit device and an external device can include generating, by the integrated circuit device, a fingerprint, where the fingerprint is reproducible and represents an inherent manufacturing process characteristic unique to the integrated circuit device. The embodiment of the method can further include receiving encrypted data from the external device, and generating a decryption key based on the fingerprint. This method can include decrypting, using the decryption key, the encrypted data to extract the data. In one embodiment, the generating the fingerprint can include determining whether a width of each of a plurality of line segments is less than a predetermined value, and generating a width value based on the act of determining, where the fingerprint is based on the width value. Alternatively, in another embodiment, the generating the fingerprint can include counting a first number of oscillations of a first oscillator during a predetermined time interval and counting a second number of oscillations of a second oscillator during the predetermined time interval, and generating a ratio between the first number and the second number, where the fingerprint is based on the ratio. In yet another embodiment, the generating the fingerprint can include determining whether a first transistor or a second transistor of each of the plurality of transistor pairs turns on earlier by detecting current flow in the first transistor and the second transistor, and generating a turn-on value based on which one of the first transistor or the second transistor of each of the plurality of transistor pairs was determined to turn on earlier where the fingerprint is based on the turn-on value. In another embodiment, the generating the fingerprint can include measuring propagation delays for a plurality of circuit elements, and combining the propagation delays to generate the fingerprint. In yet another embodiment, the generating the fingerprint can include counting a third number of oscillations of a third oscillator during the predetermined time interval in order to generate a count value, where the fingerprint is based on the count value.
Another embodiment of a method to secure communication of data between an integrated circuit device and an external device can include generating, by the integrated circuit device, a fingerprint, where the fingerprint is reproducible and represents an inherent manufacturing process characteristic unique to the integrated circuit device. The embodiment of the method can further include receiving data from the external device, and checking validity of the data using the fingerprint. In one embodiment, the generating the fingerprint can include determining whether a width of each of a plurality of line segments is less than a predetermined value, and generating a width value based on the act of determining, where the fingerprint is based on the width value. Alternatively, in another embodiment, the generating the fingerprint can include counting a first number of oscillations of a first oscillator during a predetermined time interval and counting a second number of oscillations of a second oscillator during the predetermined time interval, and generating a ratio between the first number and the second number, where the fingerprint is based on the ratio. In yet another embodiment, the generating the fingerprint can include determining whether a first transistor or a second transistor of each of a plurality of transistor pairs turns on earlier by detecting current flow in the first transistor and the second transistor, and generating a turn-on value based on which one of the first transistor or the second transistor of each of the plurality of transistor pairs was determined to turn on earlier, where the fingerprint is based on the turn-on value. In another embodiment, the generating the fingerprint can include measuring propagation delays of a plurality of circuit elements, and combining the propagation delays to generate the fingerprint. In yet another embodiment, the generating the fingerprint can include counting a third number of oscillations of a third oscillator during the predetermined time interval in order to generate a count value, where the fingerprint is based on the count value.
An embodiment of an integrated circuit device can include a fingerprint element to generate a fingerprint, where the fingerprint is reproducible and represents an inherent manufacturing process characteristic unique to the integrated circuit device. The embodiment of the integrated circuit device can further include a decryption circuit, coupled to the fingerprint element, to decrypt an encrypted data in order to extract data, where the encrypted data is decrypted using a decryption key that is based on the fingerprint. In one embodiment, the fingerprint element can include a plurality of line segments, and a sensing circuit, coupled to the plurality of line segments, to generate the fingerprint, where the fingerprint is based on a width value that is based on whether a width of each of the plurality of line segments is less than a predetermined value. In yet another embodiment, the fingerprint element can include a first oscillator, a second oscillator, and a second sensing circuit, coupled to the first oscillator and the second oscillator, to generate the fingerprint that is based on a ratio between a number of oscillations of the first oscillator and a number of oscillations of the second oscillator during the predetermined time interval. Alternatively, in another embodiment, the fingerprint element can include a plurality of transistor pairs, and a third sensing circuit, coupled to the plurality of transistor pairs, to generate the fingerprint, where the fingerprint is based on a turn-on value that is based on whether a first transistor or a second transistor of each of the plurality of transistor pairs turn on earlier when a read voltage is applied thereto. In yet another embodiment, the fingerprint element can include a plurality of circuit elements on the integrated circuit device, and a fourth sensing circuit, coupled to the plurality of circuit elements, to generate the fingerprint, where the fingerprint is based on combining propagation delays of the plurality of circuit elements. In another embodiment, the fingerprint element can include a third oscillator, and a fifth sensing circuit, coupled to the third oscillator, to generate the fingerprint, where the fingerprint is based on a count of a number of oscillations of the third oscillator during the predetermined time interval.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of an FPGA including a fingerprint element in accordance with the present invention;
FIG. 2 is a flow chart illustrating configuration of an FPGA in accordance with one embodiment of the present invention;
FIG. 3 is a block diagram illustrating one embodiment of the fingerprint element of the present invention;
FIG. 4 is a block diagram illustrating another embodiment of the fingerprint element of the present invention;
FIG. 5 is a block diagram illustrating yet another embodiment of the fingerprint element of the present invention; and
FIG. 6 is a block diagram illustrating still another embodiment of the fingerprint element of the present invention.



Like components in the Figures are similarly labeled.
DETAILED DESCRIPTION
FIG. 1 shows a circuit board 1 containing an FPGA 10 in accordance with the present invention that is connected to an encryption circuit 19 and an external storage device 20. The storage device 20 stores, in an encrypted form, configuration data that includes the bitwise representation of a desired circuit design that is to be implemented by the FPGA 10. The storage device 20 may be any non-volatile memory device, and in one embodiment is a PROM. The configuration data is provided to the encryption circuit 19, which in turn encrypts the configuration data in a well-known manner. The encryption circuit 19 provides the encrypted configuration data to the storage device 20 for storage therein. In some embodiments, the encryption circuit 19 uses a fingerprint generated by the fingerprint element 18 of the FPGA 10 as an encryption key to encrypt the configuration data, although other encryption keys may be used. Further, although shown in FIG. 1 as external to the storage device 20, in some embodiments, the encryption circuit 19 is included within the storage device 20.
The FPGA 10 includes a plurality of configurable logic elements 12, a configuration circuit 14, a decryption circuit 16, and a fingerprint element 18. The configurable logic elements 12 include well-known CLBs, IOBs, and a programmable interconnect (not shown for simplicity) that, when configured, implement the desired circuit design. In one embodiment, the configurable logic elements 12 are of the type used in the Virtex family of FPGAs available from Xilinx, Inc., 2100 Logic Drive, San Jose, Calif. 95124, although other FPGA architectures may be used in accordance with the present invention. The configuration circuit 14 is conventional, and controls the loading of configuration data into the configurable logic elements 12. The decryption circuit 16 may be any well-known circuit for decrypting the encrypted configuration data received from the storage device 20.
During power-up of the board 1, the storage device 20 transmits the encrypted configuration data stored therein to the FPGA 10. The fingerprint element 18 generates a fingerprint that is indicative of inherent manufacturing process variations characteristic of the FPGA 10. In accordance with the present invention, the decryption circuit 16 uses the fingerprint as a decryption key to decrypt the encrypted configuration data to extract the (original) configuration data. Because of the unlikelihood that any two chips will have identical manufacturing process variations, the fingerprint generated by the fingerprint element 18 is unique to the FPGA 10. Thus, by using inherent manufacturing process variations unique to the FPGA 10 to generate the fingerprint (e.g., the decryption key) each time the FPGA 10 is powered up, the FPGA 10 does not need an on-board non-volatile memory to store the decryption key, thereby saving silicon area and cost. Further, because the fabrication of the FPGA 10 does not depend on whether a particular manufacturing process technology has been developed for non-volatile memory, the FPGA 10 may be fabricated using the latest manufacturing process technology, thereby allowing for encryption of the FPGA 10's configuration data without sacrificing the competitive advantage realized by using the latest manufacturing process technology.
The competitive advantage realized by using the latest process technology, as opposed to using the previous generation process technology, is significant. For example, at present, while the latest available process for volatile memory is the 0.13 micron technology, the latest process available for non-volatile memory is the 0.25 micron technology. Since the 0.13 micron process technology produces chips that are about half as long and about half as wide as the 0.25 micron process technology, the chips produced by the 0.13 micron process technology are about one fourth the size, and therefore about one-fourth the cost, as chips produced by the 0.25 micron process technology. Thus, for example, by generating a decryption key within the FPGA 10 without using non-volatile memory, FPGAs incorporating embodiments of the present invention may be fabricated using 0.13 micron process technology. In contrast, FPGAs that include non-volatile memory to store the decryption key cannot presently be fabricated using 0.13 micron process technology, but rather must be fabricated using 0.25 micron process technology, which as discussed above is a competitive disadvantage.
Configuration of the FPGA 10 in one embodiment of the present invention is described below with reference to the flow chart of FIG. 2. During testing of the board 1, the FPGA 10 is powered up, and the fingerprint element 18 generates the fingerprint (step 21). The fingerprint is transmitted from the FPGA 10 to the encryption circuit 19 (step 22). Preferably, the fingerprint is transmitted from the FPGA 10 to the encryption circuit 19 in an encrypted form using, for example, a well-known public-key cryptography system, although other cryptography systems may be used. The encryption circuit 19 receives configuration data that embodies the circuit design desired to be implemented by the FPGA 10, and uses the fingerprint as an encryption key to encrypt the configuration data (step 23). Any suitable encryption technique may be used. The encrypted configuration data is then provided to and stored in the external storage device 20 in a well-known manner (step 24).
To configure the FPGA 10 to implement the desired circuit design, the board 1 is powered up, and the FPGA 10 waits until the power supply becomes stable at a predetermined voltage. Then, a power-on reset step resets the configurable logic elements 12 (and other elements not shown for simplicity) in a well-known manner (step 25). The external storage device 20 transmits the encrypted configuration data to the decryption circuit 16 of the FPGA 10 (step 26). The fingerprint element 18 generates the fingerprint (step 27). As mentioned earlier, the fingerprint generated by the fingerprint element 18 is a multi-bit binary representation of one or more inherent manufacturing process variations unique to the FPGA 10, and may be of any length. In one embodiment, the fingerprint is 150 bits.
The fingerprint element 18 provides the fingerprint to the decryption circuit 16, which in turn uses the fingerprint as a decryption key to decrypt the encrypted configuration data to extract the (original) configuration data (step 28). The configuration data is then provided to the configuration circuit 14, which uses the configuration data to program the configurable logic elements 12 to implement the desired circuit design (step 29). In this manner, in order to appropriate the configuration data, a person must determine the decryption key, thereby making illegal copying and/or use of the configuration data difficult.
The fingerprint element 18 may be any well-known circuit or software tool that generates a fingerprint indicative of manufacturing process variations unique to the FPGA 10. In some embodiments, differences in transistor threshold voltages caused by such process variations are used to generate the fingerprint. In one embodiment, the fingerprint element 18 includes a plurality of pairs of transistors, where differences in the threshold voltage between the transistors within each pair are used to generate a corresponding bit of the fingerprint.
Referring to FIG. 3, the fingerprint element 30, which is one embodiment of the fingerprint element 18, includes a plurality of transistor pairs 32a(1)-32b(1) to 32a(n)-32b(n) connected between a power supply VDD and a sensing circuit 34. A read voltage VR having a magnitude within the range of transistor threshold voltage variations is applied to the gates of each of the transistor pairs 32a(1)-32b(1) to 32a(n)-32b(n). Because the transistors 32a and 32b of each pair have different threshold voltages, when VR is applied thereto, one of the transistors in each pair turns on earlier than the other transistor in the pair. The sensing circuit 34 determines which transistor 32a or 32b of each transistor pair turns on earlier by, for example, detecting current flow in the transistors 32a and 32b, and in response thereto generates a corresponding bit of the n-bit fingerprint. For example, in one embodiment, for each of transistor pairs 32a(1)-32b(1) to 32a(n)-32b(n), the sensing circuit 34 generates a fingerprint bit of logic 1 if the first transistor 32a of the pair turns on before the second transistor 32b of the pair and, conversely, generates a fingerprint bit of logic 0 if the second transistor 32b of the pair turns on before the first transistor 32a of the pair. The fingerprint bits generated from corresponding transistor pairs 32a(1)-32b(1) to 32a(n)-32b(n) are combined (e.g., concatenated) to generate the n-bit fingerprint.
In some embodiments, the read voltage VR is slowly ramped from a first voltage to a second voltage, where the first voltage is less than all the threshold voltages of the transistor pairs 32a(1)-32b(1) to 32a(n)-32b(n), and the second voltage is greater than all the threshold voltages of the transistor pairs 32a(1)-32b(1) to 32a(n)-32b(n).
Because the manufacturing process variations that result in variations in transistor threshold voltages are random, the fingerprint generated by the fingerprint element 30 is unique to the FPGA 10. However, because transistor threshold voltages gradually vary over time, the fingerprint generated by the fingerprint element 30 may undesirably drift (i.e., change) over time. If allowed to drift, the fingerprint may no longer be able to decrypt the configuration data received from the external storage device 20.
Fingerprint drift may be avoided by generating the fingerprint according to manufacturing process variations that do not change over time. In one embodiment, the fingerprint element 18 includes a plurality of line segments whose deviation from a predetermined line width is used to generate corresponding bits of the fingerprint. For example, FIG. 4 shows a fingerprint element 40 including a plurality of line segments 42(1)-42(n) connected to a sensing circuit 44. For each line segment 42(1)-42(n), the sensing circuit 44 determines whether its line width is less than the predetermined line width, and generates a corresponding bit of the fingerprint accordingly. For example, if the line width of a line segment 42 is less than the predetermined line width, then the sensing circuit 44 generates a corresponding fingerprint bit of logic 0, and conversely, if the line width of the line segment 42 is not less than the predetermined line width, then the sensing circuit 44 generates a corresponding fingerprint bit of logic 1. The sensing circuit 44 may determine the relative line width of line segments 42(1)-42(n) using any well-known electrical technique. The statistical variation of the line widths may be maximized by fabricating the line widths as narrow as possible. Because line widths do not vary over time, the fingerprint generated by the fingerprint element 40 remains constant over time.
In other embodiments, propagation delays of circuit elements on the FPGA 10 are measured and used to generate the fingerprint in a well-known manner. In one embodiment, an oscillator within the FPGA 10 is used to generate the fingerprint. FIG. 5 shows a fingerprint element 50 including an oscillator 52 and a sensing circuit 54. Because transistor delays are sensitive to manufacturing process variations, which as described above are random, the specific frequency of the fingerprint oscillator 52 on the FPGA 10 is unique. To generate the fingerprint, power is applied to the oscillator 52, and the number of times that the oscillator 52 switches during a predetermined time interval is counted. The resultant binary equivalent of the oscillator count is then used as the fingerprint. Reference for the predetermined time interval, which may be of any suitable duration, may be provided by well-known delay locked loops (DLL) within the configurable logic elements 12 of the FPGA 10 (see also FIG. 1). Thus, although shown in FIG. 5 as internal to the fingerprint element 50, in other embodiments, the oscillator 52 may be external to the fingerprint element 50, e.g., the oscillator 52 is fabricated in or implemented by the configurable logic elements 12 (see also FIG. 1). In some embodiments, the oscillator 52 is implemented within a CLB by configuring the CLB as an inverter with feedback. In such embodiments, the CLB may be within either the fingerprint element 50 or the configurable logic elements 12.
However, because transistor delays are sensitive to temperature and voltage fluctuations, the frequency of the oscillator 52 may be sensitive to temperature and voltage fluctuations. As a result, the fingerprint element 50 may not generate the same fingerprint when the FPGA 10 is exposed to significant temperature or voltage fluctuations, thereby resulting in fingerprint drift. Accordingly, the following embodiments provide immunity from fingerprint drift resulting from temperature and voltage fluctuations.
In one embodiment, a ratio of oscillator counts is used to generate the fingerprint in order to eliminate the effect of temperature and voltage fluctuations. For example, FIG. 6 shows a fingerprint element 60 including first and second oscillators 62 and 64 connected to a sensing circuit 66. When power is applied, the sensing circuit 66 counts the number of times that each oscillator 62 and 64 switches during the predetermined time interval. Reference for the predetermined time interval may be provided by a DLL as described above with respect to the fingerprint element 50. The sensing circuit 66 divides the count value of one oscillator by the count value of the other oscillator to generate a ratio, the binary equivalent of which is used as the fingerprint. Because the respective frequencies of oscillators 62 and 64 vary equally over temperature and voltage fluctuations, the ratio of their resultant count values, and therefore the fingerprint generated therefrom, remains constant over temperature and voltage fluctuations. Although shown in FIG. 6 as internal to the fingerprint element 60, in other embodiments the oscillators 62 and 64 may be external to the fingerprint element 60. In some embodiments, the oscillators 62 and 64 are implemented using CLBs, as described above.
Referring again to FIG. 5, in another embodiment, the sensing circuit 50 is configured to ignore the m least significant bits of the n-bit oscillator count value provided from the oscillator 52, with the remaining n-m bits of the oscillator count value being used as the fingerprint. By truncating the m least significant bits of the oscillator count value, the resultant shortened fingerprint represents a range of oscillator count values, and therefore includes a built-in tolerance for frequency variations resulting from temperature and voltage fluctuations. However, because sensing circuit 54 must be pre-configured to ignore the m least significant bits when generating the fingerprint, the frequency range represented by shortened fingerprint is fixed. Further, if the frequency range represented by the shortened fingerprints of two or more different FPGAs 10 overlap, then the resulting decryption keys may be same, which in turn diminishes security.
While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from this invention in its broader aspects and, therefore, the appended claims encompass within their scope all such changes and modifications as fall within the true spirit and scope of this invention. For example, although in the above examples the configuration data is described as being stored in encrypted format in the storage device 20, in other embodiments, the configuration data may be stored in the storage device 20 in un-encrypted form. In such embodiments, the storage device 20 also includes a well-known encryption circuit that encrypts the configuration data using the fingerprint as the encryption key prior to its transmission to the FPGA 10. Further, although described above as using the fingerprint for both the decryption key and the encryption key, in actual embodiments, a key other than the fingerprint may be used as the encryption key.

## Claims

1. A method of securing communication of data between an integrated circuit device and an external device, the method comprising:
generating, by the integrated circuit device, a fingerprint, wherein the fingerprint is reproducible and represents an inherent manufacturing process characteristic unique to the integrated circuit device;
receiving encrypted data from the external device;
generating a decryption key based on the fingerprint; and
decrypting, using the decryption key, the encrypted data to extract the data, wherein generating the fingerprint comprises one of:
determining whether a width of each of a plurality of line segments is less than a predetermined value, and generating a width value based on the act of determining, wherein the fingerprint is based on the width value; or
counting a first number of oscillations of a first oscillator during a predetermined time interval and counting a second number of oscillations of a second oscillator during the predetermined time interval, and generating a ratio between the first number and the second number, wherein the ratio represents the fingerprint; or
determining whether a first transistor or a second transistor of each of a plurality of transistor pairs turns on earlier by detecting current flow in the first transistor and the second transistor, and generating a turn-on value based on which one of the first transistor or the second transistor of each of the plurality of transistor pairs was determined to turn on earlier, wherein the fingerprint is based on the turn-on value.

2. The method of claim 1, further comprising:
generating an encryption key using the fingerprint;
encrypting the data using the encryption key; and
storing the encrypted data in the external device.

3. The method of claim 1, wherein the fingerprint is generated during power-up of the integrated circuit device.

4. The method of claim 1, wherein the data is configuration data, and further comprising configuring the integrated circuit device using the configuration data.

5. The method of claim 1, wherein the fingerprint comprises a range of values that is less than the generated fingerprint, wherein the range of values provides a built-in tolerance for variations resulting from fluctuations.

6. The method of claim 1, wherein the fingerprint comprises a range of values of one of: the width value, the ratio, the turn-on value, the combined propagation delays, or the count value, wherein the range of values provides a built-in tolerance for variations when performing the act of determining, counting, or measuring.

7. The method of claim 1, wherein the fingerprint comprises less than all bits of a binary equivalent of the count value.

8. A method of securing communication of data between an integrated circuit device and an external device, the method comprising:
generating, by the integrated circuit device, a fingerprint, wherein the fingerprint is reproducible and represents an inherent manufacturing process characteristic unique to the integrated circuit device;
receiving data from the external device; and
checking validity of the data using the fingerprint, wherein generating the fingerprint comprises one of:
determining whether a width of each of a plurality of line segments is less than a predetermined value, and generating a width value based on the act of determining, wherein the fingerprint is based on the width value; or
counting a first number of oscillations of a first oscillator during a predetermined time interval and counting a second number of oscillations of a second oscillator during the predetermined time interval, and generating a ratio between the first number and the second number, wherein the ratio represents the fingerprint; or
determining whether a first transistor or a second transistor of each of a plurality of transistor pairs turns on earlier by detecting current flow in the first transistor and the second transistor, and generating a turn-on value based on which one of the first transistor or the second transistor of each of the plurality of transistor pairs was determined to turn on earlier, wherein the fingerprint is based on the turn-on value.

9. The method of claim 8, further comprising:
generating an encryption key using the fingerprint;
encrypting the data using the encryption key; and
storing the encrypted data in the external device,
wherein checking validity of the data using the fingerprint comprises:
generating a decryption key using the fingerprint; and
decrypting the encrypted data in the integrated circuit device using the decryption key to extract the data.

10. The method of claim 9, further comprising:
configuring the integrated circuit device using the decrypted data.

11. The method of claim 8, wherein the fingerprint comprises a range of values that is less than the generated fingerprint, wherein the range of values provides a built-in tolerance for variations resulting from fluctuations.

12. The method of claim 8, wherein the fingerprint comprises a range of values of one of: the width value, the ratio, the turn-on value, the combined propagation delays, or the count value, wherein the range of values provides a built-in tolerance for variations when performing the act of determining, counting, or measuring.

13. An integrated circuit device, comprising:
a fingerprint element to generate a fingerprint, wherein the fingerprint is reproducible and represents an inherent manufacturing process characteristic unique to the integrated circuit device;
a decryption circuit, coupled to the fingerprint element, to decrypt an encrypted data in order to extract data, wherein the encrypted data is decrypted using a decryption key that is based on the fingerprint, and
wherein the fingerprint element comprises:
a plurality of line segments; and
a first sensing circuit, coupled to the plurality of line segments, to generate the fingerprint, wherein the fingerprint is based on a width value that is based on whether a width of each of the plurality of line segments is less than a predetermined value; or
wherein the fingerprint element comprises:
a first oscillator;
a second oscillator; and
a second sensing circuit, coupled to the first oscillator and the second oscillator, to generate the fingerprint that is based on a ratio between a number of oscillations of the first oscillator and a number of oscillations of the second oscillator during a predetermined time interval wherein the ratio represents the fingerprint; or

wherein the fingerprint element comprises:
a plurality of transistor pairs; and
a third sensing circuit, coupled to the plurality of transistor pairs, to generate the fingerprint, wherein the fingerprint is based on a turn-on value that is based on whether a first transistor or a second transistor of each of the plurality of transistor pairs turn on earlier when a read voltage is applied thereto.

14. The integrated circuit device of claim 13, wherein the data is configuration data, and further comprising a configuration circuit to configure a plurality of configurable elements with the configuration data.

15. The integrated circuit device of claim 13, further comprising:
a storage device, external to the integrated circuit device, to store the encrypted data.

16. The integrated circuit device of claim 15, wherein the storage device includes an encryption circuit to encrypt the data using the fingerprint as an encryption key to generate the encrypted data.

17. The integrated circuit device of claim 13, wherein the fingerprint comprises a range of values that is less than the generated fingerprint, wherein the range of values provides a built-in tolerance for variations resulting from fluctuations.

18. The integrated circuit device of claim 13, wherein the fingerprint comprises a range of values of one of: the width value, the ratio, the turn-on value, the combined propagation delays, or the count value, wherein the range of values provides a built-in tolerance for variations when generating the fingerprint.

19. The integrated circuit device of claim 13, wherein the fifth sensing circuit ignores at least one bit of a binary equivalent of the count when generating the fingerprint.

20. The integrated circuit device of claim 13, wherein the fingerprint is generated during power-up of the integrated circuit device.