Removable storage media is often used for long term archival storage of data. The removable nature of this media lends itself to off-line and/or off-site storage of data. In many situations there are business policies, regulations, or laws that require data to be kept for minimum time, after which the data may represent a liability to the data's owner. It is often the case that this timely destruction of data that has exceeded its minimum lifespan is difficult. It is not uncommon for the physical location of removable storage media to be unknown due to errors in shipment or storage. It is also the case that removable media may be called back from the off-site vaulting location for legitimate access purposes and never returned to the vault. Another potential problem for the timely destruction of expired data is the loss of the catalog or index of the data such that the contents of individual removable storage media is unknown without reading the media, an expensive and time consuming task. Additionally it is often time consuming and labor intensive to destroy the contents of removable media even when the media is readily accessible. Finally, unencrypted data on removable media represents a risk for the loss or theft of confidential information.
Tape drives and some disk drives have had the capability of encrypting data for several years. The management of the keys used for encryption has been the responsibility of the application used to write the data to the device. Since the data contained upon an encrypted device is incomprehensible without the associated encryption keys, the loss of said keys is catastrophic. For this reason the encryption keys are typically protected by means of backup or maintenance of multiple copies. These additional copies of the encryption keys represent a liability since to effectively destroy the data on encrypted devices the device must be erased, overwritten, or all copies of the keys used to encrypt the data must be destroyed. Typically data management applications expire the catalog or index for a piece of removable media making it eligible for reuse, with no guarantees that the data on the removable media will actually be destroyed in a timely manner, if ever.
Another method employed to delete expired data is to keep the data on an on-line storage device and erase or overwrite the data upon expiration. These solutions do not face the same access time requirements and physical location challenges of removable media.
The system, method, and devices of the invention each have several aspects, no single one of which is solely responsible for its desirable attributes. Without limiting the scope of this invention, its more prominent features will now be discussed briefly. After considering this discussion, and particularly after reading the section entitled “Detailed Description of Preferred Embodiments” one will understand how the features of this invention provide advantages over other removable storage media devices.
One embodiment includes a method of data storage management, which comprises: storing data encrypted with a temporary encryption key; storing the temporary encryption key; storing an expiration condition for the temporary encryption key; determining whether the expiration condition has been satisfied; and deleting the temporary encryption key upon the expiration condition being satisfied.
In some embodiments a method may also include encrypting the temporary encryption key with a confidentiality encryption key
Another embodiment includes a method of data storage management, which comprises: storing data encrypted with a temporary encryption key on a removable data storage medium; storing the temporary encryption key on the removable data storage medium; storing an expiration condition for the temporary encryption key on the removable data storage medium; determining whether the expiration condition has been satisfied; and deleting the temporary encryption key upon the expiration condition being satisfied.
In some embodiments a method may also include removing the removable data storage media from a read/write device after storing the expiration condition and prior to determining whether the expiration condition has been satisfied.
One embodiment of a removable data storage medium device comprises: means for storing a temporary encryption key, data encrypted with the temporary encryption key, and an expiration condition; and means for deleting the temporary encryption key upon receiving an indication signal that the expiration condition has been satisfied.
Other embodiments may also include means for receiving a time-varying signal from an external source; and means for determining whether the expiration condition has been satisfied, configured to selectively generate an indication signal based on a comparison of the time-varying signal to the expiration condition.
Another embodiment of a removable data storage media device comprises: means for storing a temporary encryption key, data encrypted with the temporary encryption key, and an expiration condition; means for generating a time-varying signal; means for determining whether the expiration condition has been satisfied, configured to selectively generate an indication signal based on a comparison of the time-varying signal to the expiration condition; and means for deleting the temporary encryption key upon receiving the indication signal that the expiration condition has been satisfied.
Yet another removable data storage device comprises: a persistent data storage, configured to store data encrypted with a temporary encryption key, the temporary encryption key, and an expiration condition for the temporary encryption key; and a control circuit configured to delete the encryption key from the persistent data storage upon receiving an indication signal that the expiration condition has been satisfied.
Other embodiments also include a first circuit configured to receive a time-varying signal from an external source; and a second circuit configured to generate an indication signal based on a comparison of the time-varying signal to the expiration condition.
One embodiment of a removable data storage device comprises: a persistent data storage, configured to store data encrypted with a temporary encryption key, the temporary encryption key, and an expiration condition for the temporary encryption key; a control circuit configured to delete the encryption key from the persistent data storage upon receiving an indication signal that the expiration condition has been satisfied; a first circuit configured to provide a time-varying signal; and a second circuit configured to generate the indication signal based on a comparison of the time-varying signal to the expiration condition.
Some embodiments are configured such that the first circuit comprises a timer circuit; and the second circuit comprises a comparison circuit.
The following detailed description is directed to certain specific embodiments. However, the invention can be embodied in a multitude of different ways. In this description, reference is made to the drawings wherein like parts are designated with like numerals throughout. As will be apparent from the following description, the invention may be implemented in at least any system that is configured to encrypt data, store data, keep track of time, and delete data, such as, but not limited to removable data storage media, computers, mobile telephones, televisions, wireless devices, personal data assistants (PDAs), hand-held computers, GPS receivers/navigators, cameras, MP3 players, camcorders, game consoles, wrist watches, clocks, calculators, and other electronic devices.
Proceeding to state 104, the temporary encryption key is stored. In one embodiment the temporary encryption key is stored with the removable storage media, either on an independent storage device within the case or enclosure for the removable storage media, or on the main storage area of the media itself. In other embodiments the temporary encryption key is stored in other volatile or non-volatile memory. The temporary encryption key is used by the read/write device and may not need to be accessed by anything other than the read/write device.
In one embodiment the temporary encryption key is stored on a non-volatile device such as, but not limited to FLASH memory or EEPROM. This non-volatile memory may be accessible by both an external interface such as, but not limited to, a passive RF read/write interface and an internal circuit responsible for erasing, over-writing, or destroying the temporary encryption key upon expiration. For simplicity the term delete will be used to mean any of these operations or any other operation which renders an encryption key or data as unusable. In another embodiment the temporary encryption key may be stored on a volatile memory device such as, but not limited to SDRAM. This volatile storage may be accessible by both a small internal circuit configured to delete the temporary encryption key, and an external interface such as, but not limited to a passive RF read/write interface.
To ensure data confidentiality, the temporary encryption key itself may be encrypted with a separate encryption key (a confidentiality key). The confidentiality key may be common across all removable media, shared among distinct groups of media, or assigned on an individual basis. Since the temporary encryption key is used when present for all data access it does not provide data confidentiality. By use of a confidentiality key, the data's owner can ensure that if their removable storage media is lost or stolen it can not be read without possession of the confidentiality key. If the confidentiality key is common across all removable media for the data's owner, it may be maintained by the read/write device, by a library device, or by other devices suited for such a purpose. In cases where application software already manages device level encryption, the existing API for setting encryption keys can be used to set the confidentiality key.
Advancing to state 106, an expiration condition for the temporary encryption key is stored. In one embodiment the expiration condition is stored with the removable storage media, either on an independent storage device within the case or enclosure for the removable storage media, or on the main storage area of the media itself. In other embodiments the encryption key is stored in other volatile or non-volatile memory. An expiration date and/or timestamp may be assigned to the individual piece of removable storage media at the time that the time sensitive data is written to the media. This date and or timestamp may be tied to an offset from Greenwich Mean Time to avoid issues of media being shipped across time zones.
The policy for data storage management may include a time period for how long data may be stored. It may also include encryption key generation and encryption instructions. The policy for the lifespan and/or expiration date of data may be common across all removable storage media, it may be maintained either directly by the device that reads and writes the removable storage media, or by a library device or changer which encloses the read/write device. Typically library devices and changers already have a management interface which may be extended to manage temporary and or confidentiality encryption keys. In the case where expiration dates are implemented, a library device represents a single point where multiple read/write devices may obtain time/date information, eliminating the need for each read/write device to maintain time/date information. If the read/write device or the library device sets policy and encryption keys there is no need for application software to be modified in any way to implement this embodiment.
According to another embodiment of the method for maintaining policy and/or confidentiality keys, a simple API may be defined to allow application software control over the policy. This API need only affect the read/write device firmware. Note that most application software takes a “lowest common feature set” approach to device management, so an ISV software may or may not support such an API. The benefit of this approach is that it allows for differing policies to be applied to different pieces of removable storage media.
Moving to decision state 108, a time signal is monitored to determine if the expiration condition has been satisfied. In one embodiment a real time device may be embedded within each piece of removable media to determine when the expiration condition has been satisfied. Alternately a broadcast time source (such as, but not limited to, the radio frequency atomic clock service) may be monitored instead of maintaining an internal real time clock.
One embodiment employs the use of a lifespan timer that specifies the useful life of the data in terms of relative hours, days, weeks, and/or years. This implementation has no reliance on accurate time and date information, and uses, for example a real time clock or simple counter/timer embedded within each piece of removable media to track relative time. It is irrelevant to the mechanism whether the timer/counter is an up counter or down counter, tracking either the age of the data or the time to expiration of the data. Other timing devices may also be used, such as other electronic, mechanical, or chemical timing devices.
The same basic mechanism can be implemented without the use of a real time device or time broadcast receiver and the associated power source, thereby reducing implementation costs significantly for the removable storage media. To implement this alternative embodiment the removable storage media may be assigned an expiration date instead of a lifespan, and the device that reads the removable storage media may either have a real time clock or access to an external real time clock or broadcast time service. The device reading the data may then compare the current real time information to the expiration condition of the removable media prior to reading any data. If the removable storage media data has expired, the device may then delete the temporary encryption key for the data. The encryption keys in this embodiment do not have to be on separate storage from the removable storage media itself; in fact the keys may be stored in a dedicated area on the removable storage media. Removable storage media typically have reserved areas for internal use by the device that is used to read and write the media. This is a practical place to store the encryption keys. This embodiment relies upon the firmware or the device reading the data to destroy expired data.
While at state 108, if the monitoring mechanism determines that the expiration condition is not satisfied, the process remains at state 108, and the monitoring mechanism continues to monitor. Once the expiration condition is met, the process 100 advances to state 110 where the temporary encryption key is deleted, rendering the data effectively destroyed. This may occur in any manner, such as a read/write device deleting the key, or circuitry configured for this purpose deleting the key.
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Another embodiment may be implemented without the requirement for support from applications used to write the data to the removable storage media. A simple API may be defined to allow application software to control the policy and process.
In some embodiments no hardware modifications are necessary for many drives. Several commercially shipping read/write devices for removable media already support encryption in hardware and the ability to read/write auxiliary non-volatile storage devices present in the case or carrier for removable storage media. Minimal firmware modifications may be necessary to the read/write devices for removable storage media.
Some embodiments require a unique type of removable storage media. For those embodiments requiring the timely destruction of expired data, this mechanism represents an added value which may be associated with each piece of removable storage media. Other embodiments may use standard media; however it may still be advantageous to create a new media identifier to associate value with removable storage media.
One embodiment is self contained on the removable storage media, such that the temporary encryption key is deleted upon satisfaction of the expiration condition even if the piece of removable storage media containing the time sensitive data is lost, stolen, or stored at an off-site location with high access latency.
In some embodiments, in addition to the use of encryption for data expiration, temporary encryption keys may also be used to guard the confidentiality of data that has not yet expired.
One embodiment can guarantee that data is rendered incomprehensible, or effectively destroyed as soon as the data has out lived its useful business, regulatory, or legal life.
Some embodiments may make use of a metadata area which exists in most removable media reserved for use by the media read/write device. The metadata area often contains information such as the media type, a media identifier (similar to a serial number, but not guaranteed unique), and in the case of tape media, a directory containing offsets (typically tachometer counts) to records written to the tape. These different types of data are often referred to as metadata, and generally do not contain any information written by a user of the media, but are substantially necessary for the user data to be read. The metadata is generally used only by the removable media read/write device itself. This metadata is not limited to the types described above.
Some embodiments use the data expiration logic to destroy the metadata or set a metadata flag (do not read, for example) on the removable media. Destroying the metadata or setting a metadata flag is advantageous compared to destroying all the unencrypted data since there is much less metadata than user data, so the process can be accomplished quickly. In some embodiments this avoids the need for encryption hardware. Destroying the metadata or setting a metadata flag will make the removable media appear to the read/write device as either invalid media, blank media, or damaged media. Consequently, reading the data, though not impossible, would require significant time and expense.
While the above detailed description has shown, described, and pointed out novel features as applied to various embodiments, it will be understood that various omissions, substitutions, and changes in the form and details of the device or processes illustrated may be made by those skilled in the art without departing from the spirit of the invention. As will be recognized, the present invention may be embodied within a form that does not provide all of the features and benefits set forth herein, as some features may be used or practiced separately from others.
This application claims priority to U.S. Provisional Application No. 60/666,913 entitled “Encryption and Encryption Key Management System for Removable Storage Media” and filed on Mar. 30, 2005, which is hereby incorporated by reference in its entirety.
Number | Date | Country | |
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60666913 | Mar 2005 | US |