Abstract:
In one embodiment, a disk drive is provided that is adapted for security authentication. The disk drive includes: a non-volatile memory storing object code; a processor for retrieving the stored object code; a decryption engine for decrypting a retrieved shared secret from the object code; and a first memory for storing the decrypted retrieved shared secret; wherein the processor is configured to overwrite the written decrypted retrieved shared secret after it has been used in an authentication procedure.

Description:
RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application No. 61/031,591, filed Feb. 26, 2008, the contents of which are incorporated by reference. 
    
    
     BACKGROUND 
     Boot memory is used for processor startup. The processor begins by retrieving a command at an initial boot address and then progressively retrieves object code until it is configured. There are many circumstances where the source code contains a secret that must be protected from unauthorized users and third parties. For example, an authentication procedure may be performed between two parties where each party proves possession of a shared secret—once either party proves to the other that it is in possession of the shared secret, the devices proves to be a trusted party. If the shared secret is compromised, unauthorized parties may be authenticated, which destroys desired security. If the object code is stored as clear text, then such a shared secret could be compromised by simply reading the non-volatile memory at the proper address. 
     Accordingly, there is a need in the art for encryption devices and methods for protecting sensitive information that is stored in object code. 
     SUMMARY 
     In accordance with an embodiment of the invention, a disk drive is provided that includes: a non-volatile memory storing object code; a processor for retrieving the stored object code; a decryption engine for decrypting a retrieved shared secret from the object code; and a first memory for storing the decrypted retrieved shared secret; wherein the processor is configured to overwrite the written decrypted retrieved shared secret after it has been used in an authentication procedure. 
     In accordance with an embodiment of the invention, a method is provided that includes the acts of: within a disk drive, retrieving object code from a non-volatile memory, the object code containing an encrypted secret; decrypting the encrypted retrieved secret within a decryption engine within the disk drive; writing the decrypted retrieved secret to a first memory; using the stored decrypted retrieved secret to authenticate the disk drive to a host; and writing over the stored decrypted retrieved secret to erase it from the memory. 
    
    
     
       DESCRIPTION OF FIGURES 
         FIG. 1  shows an example disk drive with an embedded decryption engine. 
         FIG. 2  is a flowchart for the decryption method practiced by the drive of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to one or more embodiments of the invention. While the invention will be described with respect to these embodiments, it should be understood that the invention is not limited to any particular embodiment. On the contrary, the invention includes alternatives, modifications, and equivalents as may come within the spirit and scope of the appended claims. Furthermore, in the following description, numerous specific details are set forth to provide a thorough understanding of the invention. The invention may be practiced without some or all of these specific details. In other instances, well-known structures and principles of operation have not been described in detail to avoid obscuring the invention. 
     Turning now to  FIG. 1 , an example device  100  is shown that includes a non-volatile memory storing object code that contains an encrypted secret. Device  100  includes a processor  102  (or other startup engine) that retrieves the object code from non-volatile memory  101  to begin, for example, a boot-up procedure. Thus, during the boot-up of processor  102 , the encrypted secret is retrieved. Processor  102  is configured to recognize this encrypted secret through, for example, an appropriate header or other identification means. Alternatively, processor  102  may be hard-wired to recognize a certain address within non-volatile memory  101  as the location for the encrypted secret. It will be appreciated that more than one encrypted secret may be stored in non-volatile memory  101  such that the discussion of retrieving a single encrypted secret is illustrative only and not intended to be limiting. 
     Once processor  102  has retrieved the encrypted secret, a decryption engine  103  within disk drive  100  decrypts the encrypted secret to produce the secret in clear text form. Because decryption engine  103  is embedded within drive  100 , the decryption of the encrypted secret occurs without outside world intervention, thereby enhancing security. For example, decryption engine  103  may comprise a linear feedback shift register that generates a pseudo-random number using an initial seed stored in a non-volatile memory such as read-only memory (ROM) (not illustrated) associated with the decryption engine  103 . The initial seed is thus never communicated outside drive  100  such that a hacker would have to reverse engineer the ROM to determine the initial seed for the pseudo-random number generation, which is very difficult and expensive. It will be appreciated that other types of decryption engines may also be implemented. In addition, the decryption engine may simply comprise a software process within processor  102 . Disk drive  100  may include any suitable drive, such as a USB FLASH drive, a DVD drive, or a magnetic hard disk drive. 
     Once the decryption engine  103  has decrypted the retrieved secret, it may be used by drive  100  such as in an authentication procedure. For example, processor  102  may write the decrypted secret to a non-volatile memory such as a plurality of registers  104 . In this fashion, the decrypted secret is available in clear text form for use by processor  102 . To preserve security of the decrypted secret, processor  102  is configured to over-write the stored clear-text secret once it has been used. 
     Turning now to  FIG. 2 , a decryption method  200  practiced by device  100  is illustrated. In step  201 , the stored object code within the non-volatile memory  101  of  FIG. 1  is retrieved along with the encrypted secret. As discussed above, the encrypted secret may be identified using an appropriate header. Alternatively, it may be stored in an identified address to identify the location of the encrypted secret. In step  202 , the decryption engine  103  decrypts the retrieved encrypted secret to provide a clear-text secret. In step  203 , the clear-text secret is written to a memory so that it may be accessed for use. For example, drive  100  may prove possession of the secret through a bus  105  to an external device. It will be appreciated that proving possession of the secret does not entail simply communicating the secret to the external world. Instead, the secret may be hashed, for example, to provide a string. This string is then communicated over bus  105  to an external device that also is in possession of the secret. By hashing its own secret and comparing the result to the string provided by drive  100 , drive  100  may be authenticated to the external device by proving possession of the secret. Finally, in step  204 , the clear-text secret is overwritten. 
     It will be appreciated that prior to method  200 , the object code (including the encrypted secret) is written to non-volatile memory  101 . Consider the advantages of this decryption method—the device will never have to communicate the clear-text secret to outside devices but instead may simply prove possession of the secret such as in a shared secret mutual authentication procedure. The clear-text secret is only stored for a limited period of time (such as the duration of the shared secret authentication procedure) and is then erased by being overwritten. Moreover, the decryption of the encrypted secret occurs within hardware (or software) within the device and is thus inherently robust to prying outsiders such as hackers attempting to gain possession of the secret. 
     The above-described embodiments are merely meant to be illustrative and not limiting. For example, the secret may be used in alternative procedures in addition to shared secret authentication. Moreover, any device that includes object code that includes an encrypted secret will benefit from the decryption methods discussed herein. It will thus be obvious to those skilled in the art that various changes and modifications may be made without departing from this invention in its broader aspects. The appended claims encompass all such changes and modifications as fall within the true spirit and scope of this invention