U.S. patent application number 14/660534 was filed with the patent office on 2016-09-22 for processor related noise encryptor.
The applicant listed for this patent is LENOVO Enterprise Solutions (Singapore) PTE. LTD.. Invention is credited to Zachary B. Durham, William M. Megarity, Matthew L. Nickerson, Brian C. Totten.
Application Number | 20160275313 14/660534 |
Document ID | / |
Family ID | 56739904 |
Filed Date | 2016-09-22 |
United States Patent
Application |
20160275313 |
Kind Code |
A1 |
Nickerson; Matthew L. ; et
al. |
September 22, 2016 |
PROCESSOR RELATED NOISE ENCRYPTOR
Abstract
An apparatus for encrypting processor related noise is
disclosed. A method and a computer program product also perform the
functions of the apparatus. The apparatus includes a frequency
selection module that selects frequencies for a first noise output.
The frequencies are within a range of frequencies of a second noise
output. The second noise output is produced by one or more first
voltage regulating modules providing power to a processor. The
apparatus includes an amplitude selection module that selects an
amplitude for each frequency of the first noise output. The
apparatus includes a noise scrambling module that produces the
first noise output based on one or both of the frequency selection
module and the amplitude selection module. The first noise output
combines with the second noise output to produce a third noise
output such that coherence between the third noise output and
operations of the processor is below a threshold.
Inventors: |
Nickerson; Matthew L.;
(Raleigh, NC) ; Durham; Zachary B.; (Durham,
NC) ; Megarity; William M.; (Raleigh, NC) ;
Totten; Brian C.; (Durham, NC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LENOVO Enterprise Solutions (Singapore) PTE. LTD. |
New Tech Park |
|
SG |
|
|
Family ID: |
56739904 |
Appl. No.: |
14/660534 |
Filed: |
March 17, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L 2209/08 20130101;
G06F 21/75 20130101; H04L 9/0662 20130101; G06F 21/72 20130101;
G06F 2221/2107 20130101 |
International
Class: |
G06F 21/75 20060101
G06F021/75; H04L 9/00 20060101 H04L009/00 |
Claims
1. An apparatus comprising: a frequency selection module that
selects a plurality of frequencies for a first noise output, the
plurality of frequencies within a range of frequencies of a second
noise output, the second noise output produced by one or more first
voltage regulating modules providing power to a processor; an
amplitude selection module that selects an amplitude for each
frequency of the plurality of frequencies of the first noise
output; and a noise scrambling module that produces the first noise
output based on one or both of the frequency selection module and
the amplitude selection module, wherein the first noise output
combines with the second noise output to produce a third noise
output such that a coherence between the third noise output and
operations of the processor is below a threshold.
2. The apparatus of claim 1, further comprising a coherence
determination module that compares the third noise output to the
operations of the processor to determine the coherence.
3. The apparatus of claim 2, further comprising a processor
monitoring module that monitors the operations of the processor and
provides data corresponding to the operations of the processor to
the coherence determination module.
4. The apparatus of claim 2, further comprising a noise detection
module that detects the third noise output and provides the third
noise output to the coherence determination module.
5. The apparatus of claim 4, wherein the noise detection module
further comprises a transducer that detects the third noise
output.
6. The apparatus of claim 1, wherein the frequency selection module
selects the plurality of frequencies for the first noise output
based at least partly on the coherence, and the amplitude selection
module selects the amplitude for each frequency of the plurality of
frequencies of the first noise output based at least partly on the
coherence.
7. The apparatus of claim 1, wherein the noise scrambling module
further comprises one or more second voltage regulating modules and
one or more loads coupled to the one or more second voltage
regulating modules, wherein the one or more second voltage
regulating modules produce the first noise output.
8. The apparatus of claim 7, wherein the one or more loads are
varied to change the first noise output.
9. The apparatus of claim 8, wherein the one or more loads are
varied by one or both of: the frequency selection module selecting
the plurality of frequencies for the first noise output; and the
amplitude selection module selecting the amplitude for each
frequency of the plurality of frequencies of the first noise
output.
10. The apparatus of claim 9, wherein the one or more loads are
varied based on the coherence between the third noise output and
the operations of the processor.
11. The apparatus of claim 8, wherein the one or more loads are
varied to produce a greater amount of the first noise output in
response to the coherence being above the threshold than in
response to the coherence being below the threshold.
12. The apparatus of claim 8, wherein the one or more loads are
varied to increase the first noise output in response to the
coherence being above the threshold.
13. The apparatus of claim 7, wherein the one or more loads further
comprise one or more transistors.
14. A method comprising: selecting a plurality of frequencies for a
first noise output, the plurality of frequencies within a range of
frequencies of a second noise output, the second noise output
produced by one or more first voltage regulating modules providing
power to a processor; selecting an amplitude for each frequency of
the plurality of frequencies of the first noise output; and
producing the first noise output based on one or both of the
plurality of frequencies and the amplitude for each frequency,
wherein the first noise output combines with the second noise
output to produce a third noise output such that a coherence
between the third noise output and operations of the processor is
below a threshold.
15. The method of claim 14, further comprising comparing the third
noise output to the operations of the processor to determine the
coherence.
16. The method of claim 14, further comprising producing a greater
amount of the first noise output in response to the coherence being
above the threshold than in response to the coherence being below
the threshold.
17. The method of claim 14, wherein producing the first noise
output based on one or both of the plurality of frequencies and the
amplitude for each frequency further comprises powering one or more
transistors based on one or both of the plurality of frequencies
and the amplitude for each frequency.
18. A system comprising: a processor; one or more first voltage
regulating modules that provide power to the processor; one or more
second voltage regulating modules that provide scrambling noise; a
frequency selection module that selects a plurality of frequencies
for a first noise output, the plurality of frequencies within a
range of frequencies of a second noise output, the second noise
output produced by the one or more first voltage regulating
modules; an amplitude selection module that selects an amplitude
for each frequency of the plurality of frequencies of the first
noise output; and a noise scrambling module that produces the first
noise output based on one or both of the frequency selection module
and the amplitude selection module, wherein the first noise output
combines with the second noise output to produce a third noise
output such that a coherence between the third noise output and
operations of the processor is below a threshold.
19. The system of claim 18, further comprising a printed circuit
board (PCB) comprising the processor, the one or more first voltage
regulating modules, the one or more second voltage regulating
modules, the frequency selection module, the amplitude selection
module, and the noise scrambling module.
20. The system of claim 18, further comprising an information
handling device that includes the processor, the one or more first
voltage regulating modules, the one or more second voltage
regulating modules, the frequency selection module, the amplitude
selection module, and the noise scrambling module.
Description
FIELD
[0001] The subject matter disclosed herein relates to processor
related noise and more particularly relates to encrypting processor
related noise.
BACKGROUND
Description of the Related Art
[0002] Information handling devices, such as desktop computers,
laptop computers, tablet computers, smart phones, optical
head-mounted display units, smart watches, etc., are ubiquitous in
society. An information handling device generally includes a
processor. Operating the processor may produce noise, such as
high-pitched sounds between 10 to 150 KHz. In certain
configurations, the noise may result from one or more voltage
regulators used to power the processor. The noise may correspond to
operations of the processor.
BRIEF SUMMARY
[0003] An apparatus for encrypting processor related noise is
disclosed. A method and a computer program product also perform the
functions of the apparatus. The apparatus includes a frequency
selection module that selects frequencies for a first noise output.
The frequencies are within a range of frequencies of a second noise
output. The second noise output is produced by one or more first
voltage regulating modules providing power to a processor. The
apparatus includes an amplitude selection module that selects an
amplitude for each frequency of the first noise output. The
apparatus includes a noise scrambling module that produces the
first noise output based on one or both of the frequency selection
module and the amplitude selection module. The first noise output
combines with the second noise output to produce a third noise
output such that a coherence between the third noise output and
operations of the processor is below a threshold.
[0004] In one embodiment, the apparatus includes a coherence
determination module that compares the third noise output to the
operations of the processor to determine the coherence. The
apparatus, in another embodiment, includes a processor monitoring
module that monitors the operations of the processor and provides
data corresponding to the operations of the processor to the
coherence determination module. In some embodiments, the apparatus
includes a noise detection module that detects the third noise
output and provides the third noise output to the coherence
determination module. In such embodiments, the noise detection
module may include a transducer that detects the third noise
output.
[0005] In one embodiment, the frequency selection module of the
apparatus selects the frequencies for the first noise output based
at least partly on the coherence, and the amplitude selection
module of the apparatus selects the amplitude for each of the first
noise output based at least partly on the coherence. In another
embodiment, the noise scrambling module of the apparatus includes
one or more second voltage regulating modules and one or more loads
coupled to the one or more second voltage regulating modules. In
such an embodiment, the one or more second voltage regulating
modules produce the first noise output. In some embodiments, the
one or more loads of the noise scrambling module are varied to
change the first noise output.
[0006] In one embodiment, the one or more loads of the noise
scrambling module are varied by one or both of the frequency
selection module selecting the frequencies for the first noise
output and the amplitude selection module selecting the amplitude
for each frequency of the first noise output. In another
embodiment, the one or more loads of the noise scrambling module
are varied based on the coherence between the third noise output
and the operations of the processor. In some embodiment, the one or
more loads of the noise scrambling module are varied to produce a
greater amount of the first noise output in response to the
coherence being above the threshold than in response to the
coherence being below the threshold. In one embodiment, the one or
more loads of the noise scrambling module are varied to increase
the first noise output in response to the coherence being above the
threshold. In another embodiment, the one or more loads of the
noise scrambling module include one or more transistors.
[0007] A method for encrypting processor related noise includes
selecting frequencies for a first noise output. The frequencies are
within a range of frequencies of a second noise output. The second
noise output is produced by one or more first voltage regulating
modules providing power to a processor. The method includes
selecting an amplitude for each frequency of the first noise
output. The method includes producing the first noise output based
on one or both of the frequencies and the amplitude for each
frequency. The first noise output combines with the second noise
output to produce a third noise output such that a coherence
between the third noise output and operations of the processor is
below a threshold.
[0008] In one embodiment, the method includes comparing the third
noise output to the operations of the processor to determine the
coherence. In another embodiment, the method includes producing a
greater amount of the first noise output in response to the
coherence being above the threshold than in response to the
coherence being below the threshold. In some embodiments of the
method, producing the first noise output based on one or both of
the frequencies and the amplitude for each frequency includes
powering one or more transistors based on one or both of the
frequencies and the amplitude for each frequency.
[0009] A system for encrypting processor related noise includes a
processor, one or more first voltage regulating modules that
provide power to the processor, and one or more second voltage
regulating modules that provide scrambling noise. The system
includes a frequency selection module that selects frequencies for
a first noise output. The frequencies are within a range of
frequencies of a second noise output. The second noise output is
produced by the one or more first voltage regulating modules. The
system includes an amplitude selection module that selects an
amplitude for each frequency of the first noise output. The system
includes a noise scrambling module that produces the first noise
output based on one or both of the frequency selection module and
the amplitude selection module. The first noise output combines
with the second noise output to produce a third noise output such
that a coherence between the third noise output and operations of
the processor is below a threshold.
[0010] In one embodiment, the system includes a printed circuit
board (PCB) including the processor, the one or more first voltage
regulating modules, the one or more second voltage regulating
modules, the frequency selection module, the amplitude selection
module, and the noise scrambling module. In another embodiment, the
system includes an information handling device that includes the
processor, the one or more first voltage regulating modules, the
one or more second voltage regulating modules, the frequency
selection module, the amplitude selection module, and the noise
scrambling module.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] A more particular description of the embodiments briefly
described above will be rendered by reference to specific
embodiments that are illustrated in the appended drawings.
Understanding that these drawings depict only some embodiments and
are not therefore to be considered to be limiting of scope, the
embodiments will be described and explained with additional
specificity and detail through the use of the accompanying
drawings, in which:
[0012] FIG. 1 is a schematic block diagram illustrating one
embodiment of a system for encrypting processor related noise in
accordance with one embodiment of the present invention.
[0013] FIG. 2 is a schematic block diagram illustrating another
embodiment of a system for encrypting processor related noise in
accordance with one embodiment of the present invention.
[0014] FIG. 3 is a schematic block diagram illustrating one
embodiment of an apparatus for encrypting processor related noise
in accordance with one embodiment of the present invention.
[0015] FIG. 4 is a schematic block diagram illustrating another
embodiment of an apparatus for encrypting processor related noise
in accordance with one embodiment of the present invention.
[0016] FIG. 5 is a schematic flow chart diagram illustrating one
embodiment of a method for encrypting processor related noise in
accordance with one embodiment of the present invention.
[0017] FIG. 6 is a schematic flow chart diagram illustrating
another embodiment of a method for encrypting processor related
noise in accordance with one embodiment of the present
invention.
[0018] FIG. 7 is a schematic flow chart diagram illustrating a
further embodiment of a method for encrypting processor related
noise in accordance with one embodiment of the present
invention.
DETAILED DESCRIPTION
[0019] As will be appreciated by one skilled in the art, aspects of
the embodiments may be embodied as a system, method or program
product. Accordingly, embodiments may take the form of an entirely
hardware embodiment, an entirely software embodiment (including
firmware, resident software, micro-code, etc.) or an embodiment
combining software and hardware aspects that may all generally be
referred to herein as a "circuit," "module" or "system."
Furthermore, embodiments may take the form of a program product
embodied in one or more computer readable storage devices storing
machine readable code, computer readable code, and/or program code,
referred hereafter as code. The storage devices may be tangible,
non-transitory, and/or non-transmission. The storage devices may
not embody signals. In a certain embodiment, the storage devices
only employ signals for accessing code.
[0020] Many of the functional units described in this specification
have been labeled as modules, in order to more particularly
emphasize their implementation independence. For example, a module
may be implemented as a hardware circuit comprising custom VLSI
circuits or gate arrays, off-the-shelf semiconductors such as logic
chips, transistors, or other discrete components. A module may also
be implemented in programmable hardware devices such as field
programmable gate arrays, programmable array logic, programmable
logic devices or the like.
[0021] Modules may also be implemented in code and/or software for
execution by various types of processors. An identified module of
code may, for instance, comprise one or more physical or logical
blocks of executable code which may, for instance, be organized as
an object, procedure, or function. Nevertheless, the executables of
an identified module need not be physically located together, but
may comprise disparate instructions stored in different locations
which, when joined logically together, comprise the module and
achieve the stated purpose for the module.
[0022] Indeed, a module of code may be a single instruction, or
many instructions, and may even be distributed over several
different code segments, among different programs, and across
several memory devices. Similarly, operational data may be
identified and illustrated herein within modules, and may be
embodied in any suitable form and organized within any suitable
type of data structure. The operational data may be collected as a
single data set, or may be distributed over different locations
including over different computer readable storage devices. Where a
module or portions of a module are implemented in software, the
software portions are stored on one or more computer readable
storage devices.
[0023] Any combination of one or more computer readable medium may
be utilized. The computer readable medium may be a computer
readable storage medium. The computer readable storage medium may
be a storage device storing the code. The storage device may be,
for example, but not limited to, an electronic, magnetic, optical,
electromagnetic, infrared, holographic, micromechanical, or
semiconductor system, apparatus, or device, or any suitable
combination of the foregoing.
[0024] More specific examples (a non-exhaustive list) of the
storage device would include the following: an electrical
connection having one or more wires, a portable computer diskette,
a hard disk, a random access memory (RAM), a read-only memory
(ROM), an erasable programmable read-only memory (EPROM or Flash
memory), a portable compact disc read-only memory (CD-ROM), an
optical storage device, a magnetic storage device, or any suitable
combination of the foregoing. In the context of this document, a
computer readable storage medium may be any tangible medium that
can contain, or store a program for use by or in connection with an
instruction execution system, apparatus, or device.
[0025] Code for carrying out operations for embodiments may be
written in any combination of one or more programming languages
including an object oriented programming language such as Python,
Ruby, Java, Smalltalk, C++, or the like, and conventional
procedural programming languages, such as the "C" programming
language, or the like, and/or machine languages such as assembly
languages. The code may execute entirely on the user's computer,
partly on the user's computer, as a stand-alone software package,
partly on the user's computer and partly on a remote computer or
entirely on the remote computer or server. In the latter scenario,
the remote computer may be connected to the user's computer through
any type of network, including a local area network (LAN) or a wide
area network (WAN), or the connection may be made to an external
computer (for example, through the Internet using an Internet
Service Provider).
[0026] Reference throughout this specification to "one embodiment,"
"an embodiment," or similar language means that a particular
feature, structure, or characteristic described in connection with
the embodiment is included in at least one embodiment. Thus,
appearances of the phrases "in one embodiment," "in an embodiment,"
and similar language throughout this specification may, but do not
necessarily, all refer to the same embodiment, but mean "one or
more but not all embodiments" unless expressly specified otherwise.
The terms "including," "comprising," "having," and variations
thereof mean "including but not limited to," unless expressly
specified otherwise. An enumerated listing of items does not imply
that any or all of the items are mutually exclusive, unless
expressly specified otherwise. The terms "a," "an," and "the" also
refer to "one or more" unless expressly specified otherwise.
[0027] Furthermore, the described features, structures, or
characteristics of the embodiments may be combined in any suitable
manner. In the following description, numerous specific details are
provided, such as examples of programming, software modules, user
selections, network transactions, database queries, database
structures, hardware modules, hardware circuits, hardware chips,
etc., to provide a thorough understanding of embodiments. One
skilled in the relevant art will recognize, however, that
embodiments may be practiced without one or more of the specific
details, or with other methods, components, materials, and so
forth. In other instances, well-known structures, materials, or
operations are not shown or described in detail to avoid obscuring
aspects of an embodiment.
[0028] Aspects of the embodiments are described below with
reference to schematic flowchart diagrams and/or schematic block
diagrams of methods, apparatuses, systems, and program products
according to embodiments. It will be understood that each block of
the schematic flowchart diagrams and/or schematic block diagrams,
and combinations of blocks in the schematic flowchart diagrams
and/or schematic block diagrams, can be implemented by code. These
code may be provided to a processor of a general purpose computer,
special purpose computer, or other programmable data processing
apparatus to produce a machine, such that the instructions, which
execute via the processor of the computer or other programmable
data processing apparatus, create means for implementing the
functions/acts specified in the schematic flowchart diagrams and/or
schematic block diagrams block or blocks.
[0029] The code may also be stored in a storage device that can
direct a computer, other programmable data processing apparatus, or
other devices to function in a particular manner, such that the
instructions stored in the storage device produce an article of
manufacture including instructions which implement the function/act
specified in the schematic flowchart diagrams and/or schematic
block diagrams block or blocks.
[0030] The code may also be loaded onto a computer, other
programmable data processing apparatus, or other devices to cause a
series of operational steps to be performed on the computer, other
programmable apparatus or other devices to produce a computer
implemented process such that the code which execute on the
computer or other programmable apparatus provide processes for
implementing the functions/acts specified in the flowchart and/or
block diagram block or blocks.
[0031] The schematic flowchart diagrams and/or schematic block
diagrams in the Figures illustrate the architecture, functionality,
and operation of possible implementations of apparatuses, systems,
methods and program products according to various embodiments. In
this regard, each block in the schematic flowchart diagrams and/or
schematic block diagrams may represent a module, segment, or
portion of code, which comprises one or more executable
instructions of the code for implementing the specified logical
function(s).
[0032] It should also be noted that, in some alternative
implementations, the functions noted in the block may occur out of
the order noted in the Figures. For example, two blocks shown in
succession may, in fact, be executed substantially concurrently, or
the blocks may sometimes be executed in the reverse order,
depending upon the functionality involved. Other steps and methods
may be conceived that are equivalent in function, logic, or effect
to one or more blocks, or portions thereof, of the illustrated
Figures.
[0033] Although various arrow types and line types may be employed
in the flowchart and/or block diagrams, they are understood not to
limit the scope of the corresponding embodiments. Indeed, some
arrows or other connectors may be used to indicate only the logical
flow of the depicted embodiment. For instance, an arrow may
indicate a waiting or monitoring period of unspecified duration
between enumerated steps of the depicted embodiment. It will also
be noted that each block of the block diagrams and/or flowchart
diagrams, and combinations of blocks in the block diagrams and/or
flowchart diagrams, can be implemented by special purpose
hardware-based systems that perform the specified functions or
acts, or combinations of special purpose hardware and code.
[0034] The description of elements in each figure may refer to
elements of proceeding figures. Like numbers refer to like elements
in all figures, including alternate embodiments of like
elements.
[0035] FIG. 1 is a schematic block diagram illustrating one
embodiment of a system 100 for encrypting processor related noise
in accordance with one embodiment of the present invention. The
system 100 includes an encryption apparatus 102 in an information
handling device 104, wherein the information handling device 104
includes memory 106, one or more first voltage regulating modules
108, a processor 110, and communication hardware 112, which are
described below. As may be appreciated, in some embodiments, one or
more of the encryption apparatus 102, the memory 106, the one or
more first voltage regulating modules 108, the processor 110, and
the communication hardware 112 may be included on a printed circuit
board (PCB). Furthermore, in some embodiments, all of the
encryption apparatus 102, the one or more first voltage regulating
modules 108, and the processor 110 may be included on the PCB.
[0036] In general, the encryption apparatus 102 provides a way to
encrypt a second noise produced by the one or more first voltage
regulating modules 108. The one or more first voltage regulating
modules 108 provide power to the processor 110. The second noise
produced by the one or more first voltage regulating modules 108
may result from operations of the processor 110. For example, the
operations of the processor 110 may vary the load placed on the one
or more first voltage regulating modules 108 resulting in the one
or more first voltage regulating modules 108 vibrating to produce
the second noise.
[0037] The encryption apparatus 102 selects frequencies for a first
noise output that are within a range of frequencies of the second
noise output. The encryption apparatus 102 selects an amplitude for
each frequency of the first noise output. Moreover, the encryption
apparatus 102 produces the first noise output based on one or both
of the frequencies and the amplitude for each frequency. The first
noise output combines with the second noise output to produce a
third noise output. The encryption apparatus 102 produces the first
noise output to result in a coherence between the third noise
output and operations of the processor 110 being below a threshold.
The encryption apparatus 102 is described in more detail with
regard to the system 200, and the apparatuses 300, 400 of FIGS. 2,
3, and 4.
[0038] The encryption apparatus 102 is depicted in the information
handling device 104, but may be located in various components and
memory of the information handling device 104. For example, the
encryption apparatus 102 may include transducers, transistors,
voltage regulators, digital signal processors, and other hardware.
In another example, the encryption apparatus 102 is implemented in
software and all or a portion may be stored in the memory 106 on
the information handling device 104. In another embodiment, the
encryption apparatus 102 is implements in software and hardware.
One of skill in the art will recognize other implementations of the
encryption apparatus 102 using hardware, software, or both.
[0039] The information handling device 104 may include any device
that generates noise relating to operations of the processor 110.
For example, in one embodiment, the information handling device 104
includes a computing device, such as a desktop computer, a laptop
computer, a personal digital assistant (PDA), a tablet computer, a
smart phone, a smart television (e.g., televisions connected to the
Internet), a set-top box, a game console, a security system
(including security cameras), a vehicle on-board computer, or the
like. In some embodiments, the information handling device 104
includes a wearable device, such as a smart watch, a fitness band,
an optical head-mounted display, or the like.
[0040] The memory 106, in one embodiment, is a computer readable
storage medium. In some embodiments, the memory 106 includes
volatile computer storage media. For example, the memory 106 may
include a random access memory (RAM), including dynamic RAM (DRAM),
synchronous dynamic RAM (SDRAM), and/or static RAM (SRAM). In some
embodiments, the memory 106 includes non-volatile computer storage
media. For example, the memory 106 may include a hard disk drive, a
flash memory, or any other suitable non-volatile computer storage
device. In some embodiments, the memory 106 includes both volatile
and non-volatile computer storage media.
[0041] In certain embodiments, the memory 106 stores data relating
to operation of the encryption apparatus 102. Moreover, in some
embodiments, the memory 106 also stores program code and related
data, such as an operating system or other controller algorithms
operating on the information handling device 104.
[0042] The one or more first voltage regulating modules 108 may
include one or more voltage regulators that provide power to the
processor 110. The one or more voltage regulators may facilitate
maintaining constant voltage levels used by the processor 110.
During operation, the one or more first voltage regulating modules
108 may produce a second noise output, such as high-pitched sounds
between 10 to 150 KHz. The second noise output produced by the one
or more first voltage regulating modules 108 may correspond
directly with operations of the processor 110. For example, the one
or more first voltage regulating modules 108 may vibrate to produce
sounds that correspond directly with a number of or frequency of
operations of the processor 110. The encryption apparatus 102 may
be used to produce a first noise output that combines with the
second noise output to produce a third noise output such that a
coherence between the third noise output and operations of the
processor 110 is below a threshold (e.g., such that the third noise
output does not correspond directly with operations of the
processor 110). As may be appreciated, in certain embodiments, the
threshold may be a predetermined threshold such as 10 percent, 20
percent, 40 percent, 50 percent, 80 percent, and so forth.
[0043] The processor 110, in one embodiment, may include any known
controller capable of executing computer-readable instructions
and/or capable of performing logical operations. For example, the
processor 110 may be a microcontroller, a microprocessor, a central
processing unit (CPU), a graphics processing unit (GPU), an
auxiliary processing unit, a field programmable gate array (FPGA),
or similar programmable controller. In some embodiments, the
processor 110 executes instructions stored in the memory 106 to
perform the methods and routines described herein. The processor
110 is communicatively coupled to the memory 106, the one or more
first voltage regulating modules 108, and the communication
hardware 112. The communication hardware 112 may facilitate
communication with other devices. For example, the communication
hardware 112 may enable communication via Bluetooth.RTM., WiFi.TM.,
and so forth.
[0044] FIG. 2 is a schematic block diagram illustrating another
embodiment of a system 200 for encrypting processor related noise
in accordance with one embodiment of the present invention. The
system 200 includes one embodiment of the information handling
device 104 having the encryption apparatus 102, the one or more
first voltage regulating modules 108, and the processor 110, which
are substantially similar to those described above in relation to
the system 100 of FIG. 1. Moreover, the one or more first voltage
regulating modules 108 include voltage regulators 202 and 204,
which are described below. The encryption apparatus 102 includes a
transducer 206, a digital signal processor 208, and a noise
generation module 210, which are also described below. Furthermore,
the noise generation module 210 includes one or more second voltage
regulating modules 212 and a load 214, which are described below. A
power supply 216 provides power to the one or more first voltage
regulating modules 108 and to the one or more second voltage
regulating modules 212.
[0045] The one or more first voltage regulating modules 108 include
the voltage regulators 202 and 204. While two voltage regulators
202 and 204 are illustrated, the one or more first voltage
regulating modules 108 may include fewer or more voltage
regulators. The voltage regulators 202 and 204 receive power from
the power supply 216 and provide regulated voltages to the
processor 110 to facilitate operations of the processor 110. In
certain embodiments, the one or more first voltage regulating
modules 108 may provide regulated voltages to the processor 110
using a device other than the voltage regulators. The one or more
first voltage regulating modules 108 produce a second noise output
during operation. The second noise output changes based on the
operations performed by the processor 110.
[0046] The transducer 206 may be any type of suitable sound sensor.
For example, the transducer 206 may be a microphone. During
operation, the transducer 206 detects the second noise output and
provides data corresponding to the detected second noise output to
the digital signal processor 208. The digital signal processor 208
receives the detected second noise output and data from the
processor 110 corresponding to operations of the processor 110.
Moreover, the digital signal processor 208 compares the second
noise output to the data corresponding to the operations of the
processor 110 to determine a coherence. If the coherence is above a
predetermined threshold, the digital signal processor 208 provides
an output to drive the noise generation module 210. However, if the
coherence is below the predetermined threshold, the digital signal
processor 208 does not provide an output to drive the noise
generation module 210. While a digital signal processor 208 is
included in the illustrated embodiment, other embodiments may use
another device capable of receiving inputs, determining an output
based on the inputs, and driving output circuitry based on the
determined output, as described herein.
[0047] The output to drive the noise generation module 210 may be
determined by the digital signal processor 208 selecting
frequencies for a first noise output to be produced by the noise
generation module 210 and/or by the digital signal processor 208
selecting an amplitude for each frequency for the first noise
output. The digital signal processor 208 produces the output to
drive the noise generation module 210 based on the frequencies
and/or the amplitude for each frequency.
[0048] The noise generation module 210 may include any suitable
electronic device capable of producing the first noise output. In
one embodiment, the noise generation module 210 includes one or
more transistors used as the load 214 for the one or more second
voltage regulating modules 212. The one or more second voltage
regulating modules 212 produce the first noise output in response
to changes in the load 214 resulting from changes to power applied
to the one or more transistors. The power supply 216 provides power
to the one or more second voltage regulating modules 212, as well
as other devices (not shown). In another embodiment, the noise
generation module 210 includes one or more transistors used as the
load 214 for the one or more first voltage regulating modules 108.
In such an embodiment, the first noise output is produced by the
one or more first voltage regulating modules 108 in conjunction
with the second noise output. Moreover, in yet another embodiment,
the noise generation module 210 incudes a transducer used to
produce the first noise output instead of the one or more second
voltage regulating modules 212 and the load 214.
[0049] While being driven by the output from the digital signal
processor 208, the noise generation module 210 produces the first
noise output. The transducer 206 senses the third noise output,
which is a combination of the first noise output and the second
noise output. As may be appreciated, first sound waves from the
first noise output meet with second sound waves from the second
noise output resulting in third sound waves of the third noise
output. The third sound waves result from constructive and/or
destructive interference as the first and second sound waves meet.
The transducer 206 provides data corresponding to the detected
third noise output to the digital signal processor 208. The digital
signal processor 208 receives the detected third noise output from
the transducer 206 and data from the processor 110 corresponding to
operations of the processor 110. Moreover, the digital signal
processor 208 compares the third noise output to the data
corresponding to the operations of the processor 110 to determine
an updated coherence. If the updated coherence is above a
predetermined threshold, the digital signal processor 208 provides
a different output to drive the noise generation module 210 than
previously provided. For example, the digital signal processor 208
may provide an output that increases or changes a frequency of the
first noise output and/or increases an amplitude of the first noise
output.
[0050] Moreover, if the coherence is below the predetermined
threshold, the digital signal processor 208 may also provide a
different output to drive the noise generation module 210 than
previously provided, or the digital signal processor 208 may
maintain the output already being provided. For example, the
digital signal processor 208 may provide an output that decreases
or changes the frequency of the first noise output and/or decreases
or changes an amplitude of the first noise output. Such a cycle may
continuously repeat for as long as desired for the encryption
apparatus 102 to encrypt the second noise output produced as a
result of the processor 110. In certain embodiments, the noise
generation module 210 may be hysteresis controlled to be either on
or off. In such embodiments, the noise generation module 210 may
turn on production of the first noise output if the coherence is
above the predetermined threshold, and may turn off production of
the first noise output if the coherence is below the predetermined
threshold. Moreover, the noise generation module 210 may turn on
production of the first noise output at fixed frequencies and
amplitudes that do not change based on the proximity of the
coherence to the predetermined threshold.
[0051] FIG. 3 is a schematic block diagram illustrating one
embodiment of an apparatus 300 for encrypting processor related
noise in accordance with one embodiment of the present invention.
The apparatus 300 includes one embodiment of the encryption
apparatus 102 with a frequency selection module 302, an amplitude
selection module 304, and a noise scrambling module 306, which are
described below.
[0052] In one embodiment, the apparatus 300 includes the frequency
selection module 302 that selects frequencies for a first noise
output. In certain embodiments, the frequencies are within a range
of frequencies of a second noise output. In such an embodiment, the
second noise output may be produced by the one or more first
voltage regulating modules 108 that provide power to the processor
110. In some embodiments, the frequency selection module 302 may
select the frequencies for the first noise output based at least
partly on a coherence between a third noise output and operations
of the processor 110. The third noise output is a combination of
the first noise output and the second noise output. In certain
embodiments, the frequency selection module 302 may select the
frequencies dynamically after detecting a range a frequencies of
the third noise output. In other embodiments, the frequency
selection module 302 may select the frequencies using hardware
and/or software and based on predetermined frequencies. For
example, the frequency selection module 302 may include hardware
designed to output driving signals to the noise scrambling module
306 at a single frequency set by the hardware. As another example,
the frequency selection module 302 may include software designed to
output driving signals to the noise scrambling module 306 at a hard
coded frequency. In one embodiment, the frequency selection module
302 may select the frequencies for the first noise output to
generate white noise within a range of frequencies similar to the
second noise output.
[0053] In one embodiment, the apparatus 300 includes the amplitude
selection module 304 that selects an amplitude for each frequency
of the first noise output. In some embodiments, the amplitude
selection module 304 may select the amplitude for each frequency
for the first noise output based at least partly on the coherence
between the third noise output and the operations of the processor
110. In certain embodiments, the amplitude selection module 304 may
select the amplitude dynamically after detecting an amplitude of
the third noise output. In other embodiments, the amplitude
selection module 304 may select the amplitudes using hardware
and/or software and based on predetermined amplitudes. For example,
the amplitude selection module 304 may include hardware designed to
output driving signals to the noise scrambling module 306 at a
single amplitude set by the hardware. As another example, the
amplitude selection module 304 may include software designed to
output driving signals to the noise scrambling module 306 at a hard
coded amplitude. In one embodiment, the amplitude selection module
304 may select that all amplitudes are the same, while in another
embodiment the amplitude selection module 304 may select a
different amplitude for different frequencies. For example, the
amplitude selection module 304 may select amplitudes for certain
frequencies to match or interfere with certain frequencies of the
second noise output to decrease coherence.
[0054] In one embodiment, the frequency selection module 302
selects frequencies different than frequencies of the second noise
output and/or the amplitude selection module 304 selects amplitudes
of the frequencies to fill in between frequencies of the second
noise output so that the combined third noise output has a
coherence lower than a threshold or lower than the second noise
output. In another embodiment, the frequency selection module 302
selects frequencies similar to those of the second noise output but
out of phase and the amplitude selection module 304 selects
amplitudes for certain frequencies of the second noise output to
cancel or attenuate frequencies of the second noise output. One of
skill in the art will recognize other ways to select frequencies
and amplitudes to reduce coherence between the third noise output
and the operations of the processor 110.
[0055] In some embodiments, the apparatus 300 includes the noise
scrambling module 306 that produces the first noise output based on
one or both of the frequency selection module 302 and the amplitude
selection module 304. The first noise output combines with the
second noise output to produce a third noise output such that the
coherence between the third noise output and operations of the
processor 110 is below a threshold. In some embodiments, the noise
scrambling module 306 may produce the first noise output as white
noise at preselected frequencies and/or amplitudes to reduce the
coherence between the third noise output and the operations of the
processor 110. Furthermore, in one embodiment, the noise scrambling
module 306 may produce the first noise output in proportion to a
difference between the coherence and the threshold such that in
response to a large difference, the frequency and/or the amplitude
are adjusted more than while the difference is small.
[0056] In one embodiment, the noise scrambling module 306 may be
used to optimize noise uniformity in the third noise output, while
in other embodiments, the noise scrambling module 306 may be used
to cancel out the second noise output. Optimizing noise uniformity
may mean that the noise scrambling module 306 generates random
noise that changes based on operations of the processor 110 to mask
the operations of the processor 110. In some embodiments, the noise
scrambling module 306 produces the second noise output at
frequencies and/or amplitudes that are outside the range of human
hearing.
[0057] The noise scrambling module 306 may include any suitable
electronic device capable of producing the first noise output. For
example, in one embodiment, the noise scrambling module 306 may
include one or more transistors used as the load 214 for the one or
more second voltage regulating modules 212. In other embodiments,
the load 214 may include resistors or other components that draw
power and create a variable load. The one or more second voltage
regulating modules 212 produce the first noise output in response
to changes in the load 214 resulting from changes to power applied
to the one or more transistors. Moreover, in another embodiment,
the noise scrambling module 306 includes a transducer used to
produce the first noise output.
[0058] FIG. 4 is a schematic block diagram illustrating another
embodiment of an apparatus 400 for encrypting processor related
noise in accordance with one embodiment of the present invention.
The apparatus 400 includes one embodiment of the encryption
apparatus 102 with the frequency selection module 302, the
amplitude selection module 304, and the noise scrambling module
306, which are substantially similar to those described above in
relation to the apparatus 300 of FIG. 3. In various embodiments,
the apparatus 400 may include a coherence determination module 402,
a processor monitoring module 404, a noise detection module 406,
and one or more second voltage regulating modules 408, which are
described below. In one embodiment, the second voltage regulating
modules 408 of the apparatus 400 of FIG. 4 are substantially
similar to the second voltage regulating module 212 of the system
200 of FIG. 2.
[0059] In one embodiment, the apparatus 400 includes the coherence
determination module 402 that compares the third noise output to
the operations of the processor 110 to determine the coherence. For
example, the coherence determination module 402 may receive the
third noise output from the noise detection module 406 and may
receive data corresponding to the operations of the processor 110
from the processor monitoring module 404. Moreover, in some
embodiments, the coherence determined by the coherence
determination module 402 may quantify how closely the third noise
output matches with the data corresponding to the operations of the
processor 110. For example, the third noise output may match the
data corresponding to the operations of the processor 110 by 10
percent, 20 percent, 40 percent, 50 percent, 80 percent, 90
percent, and so forth and therefore have a coherence of such. In
certain embodiments, the coherence may be quantified as a
percentage of time that the third noise output corresponds with the
data corresponding to the operations of the processor 110. For
example, the coherence may be 10 percent, 20 percent, 40 percent,
50 percent, 80 percent, 90 percent, and so forth.
[0060] In certain embodiments, the coherence may be calculated
using the following formula:
C xy ( f ) = G xy ( f ) 2 G xx ( f ) G yy ( f ) ##EQU00001##
[0061] To use this formula, x(t) and y(t) are two signals used. For
example, x(t) may represent the third noise output and y(t) may
represent the data corresponding to the operations of the processor
110. G.sub.xy(f) is the cross-spectral density between x and y, and
G.sub.xx(f) and G.sub.xy(f) are the autospectral density of x and y
respectively.
[0062] In some embodiments, a high coherence may be used to
correlate the third noise output with specific operations of the
processor 110, such as operations involving user authentication,
data encryption, use of encryption keys, and the like. In such
embodiments, passwords, encryption algorithms, encryption keys, and
the like may be obtained by monitoring the third noise output or
the second noise output if the encryption apparatus 102 is not
present or functioning. However, reducing the coherence between the
third noise output and the specific operations of the processor 110
also reduces the likelihood that passwords, encryption algorithms,
encryption keys, and the like may be obtained by monitoring the
third noise output. As such, a low coherence may show little
correlation between the third noise output and specific operations
of the processor 110.
[0063] The apparatus 400, in another embodiment, includes the
processor monitoring module 404 that monitors the operations of the
processor 110 and provides data corresponding to the operations of
the processor 110 to the coherence determination module 402. For
example, the processor monitoring module 404 may monitor a rate
that operations of the processor 110 are performed, a frequency of
operations of the processor 110, a number of operations of the
processor 110 per time stamp, a number of operations per a
predetermined time period, a periodicity of operations of the
processor 110, and so forth. The data corresponding to the
operations of the processor 110 may be provided to the coherence
determination module 402 in real-time, or with a delay.
[0064] In some embodiments, the processor monitoring module 404 may
monitor commands and/or data communicated with the processor 110.
Furthermore, in one embodiment, the processor monitoring module 404
may monitor types of operations performed by the processor 110. The
processor monitoring module 404 may monitor any operation of the
processor 110 with sensitive information that may correlate to the
second noise output with a high coherence where monitoring the
second noise output could reveal the sensitive information. The
encryption apparatus 102 reduces the coherence between the
processor operations with the sensitive information and the second
noise output by producing a first noise output that combines with
the second noise output to reduce coherence so that discovering the
sensitive information is more difficult or is not possible.
[0065] In one embodiment, the apparatus 400 includes the noise
detection module 406 that detects the third noise output and
provides the third noise output to the coherence determination
module 402. In some embodiments, the noise detection module 406
includes the transducer 206 that detects the third noise output.
The transducer 206 may be any suitable sound sensor, such as a
microphone. As may be appreciated, the noise detection module 406
may be positioned adjacent to the one or more first voltage
regulating modules 108 that provide power to the processor 110.
Specifically, the noise detection module 406 may be positioned
adjacent to the voltage regulators 202 and 204, which may more
accurately detect the second noise output. Furthermore, the noise
detection module 406 may be positioned adjacent to the one or more
second voltage regulating modules 408. In some embodiments, the one
or more first voltage regulating modules 108 may be positioned
adjacent to the one or more second voltage regulating modules 408.
Placing the one or more second voltage regulating modules 408
adjacent to the one or more first voltage regulating modules 108
may aid in combining the first and second noise outputs.
Accordingly, the noise detection module 406 may receive noise
produced by the one or more first voltage regulating modules 108
that provide power to the processor 110 and noise produced by the
one or more second voltage regulating modules 408.
[0066] In certain embodiments, the noise detection module 406 may
compute a noise produced by the one or more first voltage
regulating modules 108 and/or the one or more second voltage
regulating modules 408. The computation may be performed using
operational specifications corresponding to the one or more first
voltage regulating modules 108 and/or the one or more second
voltage regulating modules 408. Furthermore, the computation may
use data corresponding to the operations of the processor 110 for
computing the noise produced by the one or more first voltage
regulating modules 108. In addition, the computation may use data
corresponding to driving the one or more second voltage regulating
modules 408 for computing the noise produced by the one or more
second voltage regulating modules 408.
[0067] The apparatus 400, in another embodiment, includes the one
or more second voltage regulating modules 408 as part of the noise
scrambling module 306. In some embodiments, the noise scrambling
module 306 also includes one or more loads 214 coupled to the one
or more second voltage regulating modules 408. In such embodiments,
the one or more second voltage regulating modules 408 produce the
first noise output. In some embodiments, the one or more loads 214
are varied to change the first noise output.
[0068] In certain embodiments, the one or more loads 214 may be
varied by the frequency selection module 302 selecting the
frequencies for the first noise output, and by the amplitude
selection module 304 selecting the amplitude for each frequency of
the first noise output. In such embodiments, voltages and/or
currents provided to the one or more loads 214 may be selected
based on the selected frequencies and/or amplitudes. Moreover, in
some embodiments, the one or more loads 214 may be varied based on
the coherence between the third noise output and the operations of
the processor 110.
[0069] In some embodiments, the one or more loads 214 may be varied
to produce a greater amount of the first noise output in response
to the coherence being above the threshold than in response to the
coherence being below the threshold. In one embodiment, the one or
more loads 214 are varied to increase the first noise output in
response to the coherence being above the threshold. In another
embodiment, the one or more loads 214 include one or more
transistors. In such an embodiment, the one or more transistors may
be electrically coupled to the one or more second voltage
regulating modules 212. The current draw of the one or more
transistors may be increased to increase the load placed on the one
or more second voltage regulating modules 212 and/or the current
draw of the one or more transistors may be decreased to decrease
the load placed on the one or more second voltage regulating
modules 212. By changing the load placed on the one or more second
voltage regulating modules 212, the first noise output produced by
the one or more second voltage regulating modules 212 is changed.
In some embodiments, the one or more loads 214 may include any
suitable load, such as one or more of resistors, variable
resistors, capacitors, inductors, transistors, a power supply
feeding a bus, or the like.
[0070] FIG. 5 is a schematic flow chart diagram illustrating one
embodiment of a method 500 for encrypting processor related noise
in accordance with one embodiment of the present invention. The
method 500 begins and selects 502 frequencies for a first noise
output. In certain embodiments, the frequency selection module 302
may select 502 the frequencies for the first noise output. The
frequencies may be within a range of frequencies of a second noise
output. The second noise output may be produced by one or more
first voltage regulating modules 108 providing power to a processor
110.
[0071] The method 500 selects 504 an amplitude for each frequency
of the first noise output. In some embodiments, the amplitude
selection module 304 may select 504 the amplitude for each
frequency of the first noise output. The method 500 produces 506
the first noise output based on one or both of the frequencies and
the amplitude for each frequency and the method 500 ends. In one
embodiment, the noise scrambling module 306 may produce 506 the
first noise output based on one or both of the frequencies and the
amplitude for each frequency. The first noise output may be
combined with the second noise output to produce a third noise
output such that a coherence between the third noise output and
operations of the processor 110 is below a threshold. In some
embodiments, the method 500 may produce a greater amount of the
first noise output in response to the coherence being above the
threshold than in response to the coherence being below the
threshold. Furthermore, in some embodiments, the method 500 may
produce the first noise output by powering one or more transistors
based on one or both of the frequencies and the amplitude for each
frequency.
[0072] FIG. 6 is a schematic flow chart diagram illustrating
another embodiment of a method 600 for encrypting processor related
noise in accordance with one embodiment of the present invention.
The method 600 detects 602 a third noise output. In some
embodiments, the noise detection module 406 may detect 602 the
third noise output. Moreover, the method 600 receives 604 data
corresponding to operations of a processor 110. In certain
embodiments, the processor monitoring module 404 may receive 604
the data corresponding to the operations of the processor 110. The
method 600 compares 606 the third noise output to the operations of
the processor 110 to determine the coherence. In one embodiment,
the coherence determination module 402 may compare 606 the third
noise output to the operations of the processor 110 to determine
the coherence.
[0073] The method 600 determines 608 whether the coherence is below
a threshold. In some embodiments, the noise scrambling module 306
may determine 608 whether the coherence is below the threshold,
while in other embodiments, the coherence determination module 402
may determine 608 whether the coherence is below the threshold. If
the method 600 determines 608 that the coherence is below a
threshold, the method 600 returns to detecting 602 the third noise
output. However, if the method 600 determines 608 that the
coherence is not below the threshold, the method 600 selects 610
frequencies for a first noise output. In one embodiment, the
frequency selection module 302 may select 610 frequencies for the
first noise output. The frequencies may be within a range of
frequencies of a second noise output. The second noise output may
be produced by one or more first voltage regulating modules 108
providing power to the processor 110.
[0074] The method 600 selects 612 an amplitude for each frequency
of the first noise output. In some embodiments, the amplitude
selection module 304 may select 612 the amplitude for each
frequency of the first noise output. The method 600 produces 614
the first noise output based on one or both of the frequencies and
the amplitude for each frequency. In certain embodiments, the noise
scrambling module 306 may produce 614 the first noise output based
on one or both of the frequencies and the amplitude for each
frequency. The first noise output may combine with the second noise
output to produce the third noise output such that the coherence
between the third noise output and the operations of the processor
110 is below the threshold. The method 600 may then return to
detecting 602 the third noise output. As may be appreciated, both
the frequencies and the amplitudes for the first noise output may
vary to produce the first noise output. However, in certain
embodiments, the amplitudes may remain constant and not be selected
with each iteration, while the frequencies vary. In contrast, in
other embodiments, such as the embodiment described in FIG. 7, the
frequencies may remain constant and not be selected with each
iteration, while the amplitudes vary.
[0075] FIG. 7 is a schematic flow chart diagram illustrating a
further embodiment of a method 700 for encrypting processor related
noise in accordance with one embodiment of the present invention.
The method 700 selects 702 frequencies for a first noise output. In
one embodiment, the frequency selection module 302 may select 702
frequencies for the first noise output. The frequencies may be
within a range of frequencies of a second noise output so that the
first noise output may be used to decrease the coherency between a
third noise output and operations of a processor 110. To set the
frequencies within a range of frequencies of the second noise
output, the range of frequencies of the second noise output may be
detected, calculated, and/or determined based on the operation or
specifications of the components producing the second noise output.
In some embodiments, the second noise output may be produced by one
or more first voltage regulating modules 108 providing power to the
processor 110. The method 700 detects 704 the third noise output.
In some embodiments, the noise detection module 406 may detect 704
the third noise output. Moreover, the method 700 receives 706 data
corresponding to the operations of the processor 110. In certain
embodiments, the processor monitoring module 404 may receive 706
data corresponding to the operations of the processor 110. The
method 700 compares 708 the third noise output to the operations of
the processor 110 to determine the coherence. In one embodiment,
the coherence determination module 402 may compare 708 the third
noise output to the operations of the processor 110.
[0076] The method 700 determines 710 whether the coherence is below
a threshold. In some embodiments, the noise scrambling module 306
may determine 710 whether the coherence is below the threshold,
while in other embodiments, the coherence determination module 402
may determine 710 whether the coherence is below the threshold. If
the method 700 determines 710 that the coherence is below a
threshold, the method 700 returns to detecting 704 the third noise
output. However, if the method 700 determines 710 that the
coherence is not below threshold, the method 700 selects 712 an
amplitude for each frequency of the first noise output. In certain
embodiments, the amplitude selection module 304 may select 712 the
amplitude for each frequency of the first noise output. In certain
embodiments, the amplitude selection module 304 may select 712 the
amplitude for only some frequencies of the first noise output. The
method 700 produces 714 the first noise output based on one or both
of the frequencies and the amplitude for each frequency. In one
embodiment, the noise scrambling module 306 may produce 714 the
first noise output based on one or both of the frequencies and the
amplitude for each frequency. The first noise output may combine
with the second noise output to produce the third noise output such
that the coherence between the third noise output and the
operations of the processor 110 is below the threshold. The method
700 may then return to detecting 704 the third noise output.
[0077] Embodiments may be practiced 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 the
foregoing description. All changes which come within the meaning
and range of equivalency of the claims are to be embraced within
their scope.
* * * * *