Abstract:
A method for securing data includes encrypting the data and storing a key ( 54 ) for deciphering the encrypted data in a volatile memory ( 56 ) coupled to a power source ( 62 ). In response to an event indicative of a vulnerability of the data to unauthorized exposure, the power source is disconnected from the volatile memory.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to data security, and, more specifically, to the protection of program code and operating data. 
       BACKGROUND OF THE INVENTION 
       [0002]    Valuable information is frequently encrypted so as to prevent or hinder unauthorized access. Encryption is only useful, however, if the associated cryptographic keys are also protected. A standard for cryptographic key protection has been published by the United States National Institute of Standards and Technology (NIST) as the “Federal Information Processing Standards Publication (FIPS PUB) 140-2: Security Requirements for Cryptographic Modules,” which is incorporated herein by reference. 
         [0003]    Hardware devices for the protection of cryptographic keys and of other critical security parameters (CSPs) are generally referred to as hardware security modules (HSMs). CSPs may include private keys used in public-key cryptography, as well as symmetric keys and passwords. Many HSMs have processing capabilities for performing cryptographic tasks. Typically, CSPs cannot be extracted from the HSMs in an unencrypted form (also referred to as a plaintext form). For backup purposes, CSPs may be removed from HSMs in encrypted form. 
         [0004]    Commercial HSMs include:
       the Host Security Module 8000 by Thales, described at www.thales-esecurity.com/productsservices;   the DEP/T6 Data Encryption Peripheral by Banksys (Brussels), described at www.banksys.com/bkscomwt/EN/Products_and_solutions/Hardware_security_modules/DEPT6/index.jsp;   the Sun Crypto Accelerator 6000 adapter (SCA6000), by Sun Microsystems, described at www.sun.com/products/networking/sslaccel/suncryptoaccel6000/index.xml; and   the 4764 PCI-X Cryptographic Coprocessor by IBM, described at www-03.ibm.com/security/cryptocards/pcixcc/overhardware.shtml.
 
The IBM 4764 module “incorporates physical penetration, power, and temperature sensors to detect physical attacks against the encapsulated subsystem.”
       
 
         [0009]    An Unmanned Aerial Vehicle (UAV), when designed for military reconnaissance, is often equipped with a mechanism for physical self-destruction in order to prevent highly confidential equipment and data from being acquired by an enemy. According to the website www.aeronautics.ru, an early Soviet Union UAV, the Tu-123, was designed to self-destruct by shutting down its own engine, thereby causing itself to crash. Modern methods of self destruction including on-board explosives are described in  Smart Weapons: Top Secret History of Remote Controlled Airborne Weapons , by Hugh McDaid and David Oliver (Welcome Rain Press, New York, N.Y. 2000). 
       SUMMARY OF THE INVENTION 
       [0010]    Embodiments of the present invention provide methods and apparatus for preventing unauthorized access to valuable data by making the data inaccessible when a vulnerability, such as a threat to data security, is sensed. 
         [0011]    In some embodiments, valuable data, such as program code and/or acquired data, is encrypted, and the associated cryptographic key is retained in volatile memory, such as random access memory (RAM). The volatile memory can retain the key only while connected to a power source. When a threat to the security of the data arises (meaning an event that could lead to exposure of the data), a trigger disconnects the power source from the memory. Consequently, the key in the memory is lost, and the data can no longer be accessed. 
         [0012]    There is therefore provided, in accordance with an embodiment of the present invention, a method for securing data including: 
         [0013]    encrypting the data; 
         [0014]    storing a key for deciphering the encrypted data in a volatile memory coupled to a power source; and 
         [0015]    in response to an event indicative of a vulnerability of the data to unauthorized exposure, disconnecting the power source from the volatile memory. 
         [0016]    Typically, disconnecting the power source includes receiving a signal indicative of the possible exposure and disconnecting the power source responsively to the signal. Receiving the signal may include sensing one or more of an environmental parameter, a circuit component failure, and an unauthorized intrusion. 
         [0017]    In some embodiments, the volatile memory is a first memory, and the method includes storing the encrypted data in a second memory. 
         [0018]    The data may include program code, and the method may include decrypting the program code using the key and passing the decrypted program code to a processor for execution. 
         [0019]    The volatile memory may be coupled to the power source by a switch, in which case disconnecting the power source includes opening the switch. 
         [0020]    In some embodiments, disconnecting the power source includes providing a logical low output from a logical switch. 
         [0021]    There is further provided, in accordance with an embodiment of the present invention, apparatus for securing data including: 
         [0022]    a volatile memory operative to store a cryptographic key; 
         [0023]    a processor, which is operative to read encrypted data and to decrypt the data using the cryptographic key in the volatile memory; 
         [0024]    a power source; and 
         [0025]    a switch, which is coupled between the power source and the volatile memory and is operative, in response to an event indicative of a vulnerability of the data to unauthorized exposure, to disconnect the power source from the volatile memory. 
         [0026]    Typically, the switch is operative to disconnect the power source upon receiving a signal indicative of the possible exposure. 
         [0027]    In some embodiments, the switch includes a relay contact. 
         [0028]    The switch may be operative to disconnect the power source upon receiving a logical low output from a sensor. 
         [0029]    The present invention will be more fully understood from the following detailed description of the embodiments thereof, taken together with the drawings in which: 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0030]      FIG. 1  is a schematic, pictorial illustration of a system in which a control unit may be configured to protect data against enemy access, in accordance with an embodiment of the present invention; and 
           [0031]      FIG. 2  is a block diagram that schematically illustrates a control unit that protects valuable data, in accordance with an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0032]      FIG. 1  is a schematic, pictorial illustration of a system  20  in which a control unit  22  performs data acquisition and computing functions. Control unit  22  is shown as being on board an unmanned aerial vehicle (UAV)  24 . 
         [0033]    In some embodiments, data acquisition by control unit  22  is performed during military reconnaissance operations. Reconnaissance may include image acquisition by a camera  26 , as well as acquisition of environmental measures, such as temperature and humidity and other atmospheric parameters. 
         [0034]    Typically, control unit  22  is configured to receive commands, such as navigation instructions, from a command center  28 . Control unit  22  may transmit images and other acquired data to command center  28  in real time, by means of a transmitter/receiver  30 . Alternatively or additionally, computing and data acquisition functions may be performed without real time communications, and control unit  22  may operate in an autonomous manner, performing tasks based solely on internally programmed code. 
         [0035]    Both the program code and the acquired data are forms of valuable data that must be protected against unauthorized access. When a vulnerability or susceptibility to data exposure is sensed, control unit  22  causes the data to become irretrievable, as described further hereinbelow. The protection against unauthorized access, referred to hereinbelow as data self-destruction, is an alternative, or complement, to physical self-destruction that is often employed in the military context described above. 
         [0036]    Although the pictured embodiment refers, by way of example, to a particular application in UAV  24 , the principles of the present invention may similarly be applied in other applications in which data and/or program code must be protected from falling into unauthorized hands. These principles may be applied not only in military and security-related fields, but also to computing devices in non-military environments, including commercial computers, that must provide active means for protecting valuable data. 
         [0037]      FIG. 2  is a block diagram that schematically illustrates elements of a control unit  22  configured to prevent unauthorized access to data, in accordance with an embodiment of the present invention. 
         [0038]    A main processor  42  of control unit  22  performs data control operations, such as reception of acquired data  44  from camera  26  and generation of output signals. Some or all of the operations performed by control unit  22  are determined by program code  50 . Acquired data  44  may also include location coordinates from a global positioning system (GPS) receiver  46 . Output signals generated by main processor  42  may be transmitted through an output driver  48  to control the path and operation of UAV  24 . Main processor  42  may also communicate with command center  28  over transmitter/receiver  30 . 
         [0039]    Program code  50  and/or acquired data  44  are encrypted and stored in a data storage area  52 . Data storage area  52  may be implemented using any data storage technology, including hard disks, solid state memory such as flash memory or random access memory (RAM), compact disks, and magnetic tapes. Data storage area  52  may therefore be understood as comprising either volatile or non-volatile memory, and furthermore may comprise multiple homogeneous or heterogeneous types of storage. 
         [0040]    A cryptographic processor  60  encrypts all data sent from main processor  42  to data storage area  52  and decrypts all data read by main processor  42  from data storage area  52 , including program code  50 . 
         [0041]    The cryptographic processor is typically comprised in a cryptographic unit  58 , which also maintains one or more cryptographic keys  54 . The cryptographic processor may execute a publicly-known cryptographic algorithm, such as the triple Data Encryption Standard (3DES) or the Advanced Encryption Standard (AES), or may execute a proprietary cryptographic algorithm. The cryptographic keys for performing the abovementioned cryptographic functions are stored in a volatile memory  56  of the cryptographic unit. 
         [0042]    Operation of control unit  22  is initialized by several steps including: encrypting and storing program code  50  in data storage area  52 , connecting volatile memory  56  to a power source, and loading the cryptographic keys into the volatile memory. Initial encryption of program code  50  may be performed by cryptographic unit  58  or by an external processor. 
         [0043]    Cryptographic unit  58  may be implemented as a single hardware module, such that elements comprised in the cryptographic unit are powered by a common power source such as a battery  62 . Battery  62  is coupled to the cryptographic unit through a switch, indicated in  FIG. 2  by way of example as a logical AND switch  64 . Switch  64  serves to receive several inputs and, if the inputs indicate that a set of necessary conditions are met, to output a logical high voltage. Switch  64  may be implemented as an integrated circuit (IC) logic device, such as a logical AND gate or a programmable logic array (PLA), or as a circuit gate comprising an electromagnetic or solid state relay. Those skilled in the art may utilize alternative technologies to implement switch  64 , depending on the environment and application of control unit  22 . 
         [0044]    Cryptographic unit  58  also may be implemented by alternative technologies and configurations. For example, cryptographic processor  60  may comprise separate processors, one for encryption and a second for decryption. In addition, cryptographic processor  60  may be physically distinct from volatile memory  56 , in which case the output of switch  62  is coupled directly to volatile memory  56  and the cryptographic processor may receive power from a separate source. Furthermore, the logical functions of cryptographic processor  60  and of main processor  42  may be performed by a single physical processing unit (which may itself comprise multiple processors). 
         [0045]    During normal operation of control unit  22 , output of switch  64  is maintained at a logical high voltage, which provides sufficient power to operate volatile memory  56 . The logical high voltage is also referred to hereinbelow as a closed-switch setting, as this setting is the equivalent of a relay contact being closed so as to couple the battery directly to the cryptographic unit. On the other hand, a logical low output, which is essentially a zero voltage output, effectively means that the battery is disconnected from volatile memory  56 . The logical low setting of the switch is therefore referred to hereinbelow as an open-switch setting. In the open-switch setting, the contents of the volatile memory are lost, as the volatile memory no longer receives power. 
         [0046]    The setting of switch  64  is determined by inputs from one or more vulnerability sensors  66 , which measure the vulnerability of control unit  22  to unauthorized access. When sensors  66  are all operational and measure levels of vulnerability within predetermined safety ranges, these sensors provide logical inputs to switch  64  that cause the output of switch  64  to be high (switch closed). In some embodiments of the present invention, sensors  66  measure environmental parameters, such as altitude, speed, location, and temperature of the UAV. When any of these parameters are outside a predetermined safety range, thereby indicating a threat, or vulnerability, the corresponding sensor will send a signal to switch  64  causing the switch to open. For example, parameters that may be set to indicate vulnerability include a low flight altitude, an exceptional speed, a deviation from a planned flight route, or other possible indications of an impending crash. When switch  64  is configured as a logical AND gate, a sensor detecting an out-of-range parameter provides a logical low signal to the switch, thereby causing the switch to disconnect power from the cryptographic unit 
         [0047]    When power is disconnected from cryptographic unit  58 , the contents of volatile memory  56 , including keys  54 , are immediately lost. Consequently, it is no longer possible to decrypt the encrypted contents of data storage area  52 . The encrypted data are therefore inaccessible, and control unit  22  has effectively performed data self-destruction. In some embodiments, control unit  22  is no longer operational after performing data self-destruction, as program code also becomes inaccessible. 
         [0048]    Additionally or alternatively, power may be disconnected from the volatile memory by other means and due to other failure-related or threat related causes. For example, the power may be disconnected upon command by an operator of the UAV. As another example, failure of a sensor, or of switch  64  itself, also causes a logical low switch output to the cryptographic unit. 
         [0049]    In a further embodiment, additional logical inputs to switch  64  are provided by main processor  42  and by other circuit components within control unit  22  to signal a failure of any of these components. Additional vulnerabilities that may be triggered by main processor  42  or other control unit elements may include loss of communications with command center  28  and reception from the command center of a specific command to cause data self-destruction. Data self-destruction may be implemented in addition to the implementation of more physical forms of self-destruction, such as physical explosion, which may be caused by an internal explosive device (not shown). Furthermore, upon destruction of the UAV (due to crash landing or explosion of such an explosive device, for example), it is likely that the power will be disconnected anyway, thus preventing unauthorized persons from salvaging and accessing the data or program code that may still be stored in non-volatile memory. 
         [0050]    In some embodiments, each UAV mission may begin with a random generation of cryptographic keys, which are then preserved only in control unit  22 . Consequently, data self-destruction is permanent, in that there is no means for reconstructing data in data storage area  52  subsequent to the disconnection of power from the cryptographic unit. In alternative embodiments, operators of control unit  22  may save a copy of the cryptographic keys, such that the data, while inaccessible to an enemy, can be reconstructed if the UAV is recovered by the operators. 
         [0051]    In some embodiments of the present invention (including non-UAV embodiments), vulnerability sensors may be configured to sense indications of unauthorized intrusion that may threaten data security. For example, vulnerability sensors may be configured to sense a forced entrance to a computing facility or to sense tampering with an enclosure of the control unit itself. 
         [0052]    The principles of the present invention may also be applied in the context of other computing or data acquisition environments, such as commercial or scientific computing operations and in the context of other communications technologies. It will thus be appreciated that embodiments described above are cited by way of example, and that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention includes both combinations and subcombinations of the various features described hereinabove, as well as variations and modifications thereof which would occur to persons skilled in the art upon reading the foregoing description and which are not disclosed in the prior art.