Electrical computers and digital processing systems: support – Data processing protection using cryptography
Reexamination Certificate
1998-02-13
2001-12-11
Decady, Albert (Department: 2132)
Electrical computers and digital processing systems: support
Data processing protection using cryptography
C713S193000, C713S152000, C380S042000, C380S201000, C705S051000
Reexamination Certificate
active
06330675
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to tile secure transfer of digital data, and more particularly, to the transfer of digital data to a local recordable storage medium while securing the transfer against unauthorized copying of the data.
2. Description of the Related Art
As a result of the continuous development of technologies, particularly in the areas of networking and communications, there has been an explosion of interest and activity in networked computer systems such as the Internet. The global growth and acceptance of networks such as the Internet has resulted in new business opportunities and new models for commerce.
One such opportunity is the use of the Internet as a distribution channel for the inexpensive transfer of digital data. For example, many companies already distribute marketing materials, technical product information, stock information, or other types of less sensitive materials over the Internet, either to potential customers or internally within the company. It would also be desirable to distribute more proprietary types of digital data, such as digitized audio tracks, literary works in digital form, or digital images and videos. If these types of data could be securely distributed to consumers, then an entirely new market for these works could be created. For example, rather than purchasing music albums from a local retail outlet, consumers could download the digital data across the Internet and then write this data to their local CD-R, thus creating their own compact disks. Similarly, rather than renting a video tape from a local video retailer, consumers could download the digital version and then play it locally on their computer screens or televisions.
The digital nature of these works, however, makes it imperative that they be secured against unauthorized copying. With no generation loss and the relative ease with which digital files may be copied and distributed, even a single unprotected copy could spawn a multitude of pirated versions, significantly reducing the demand for authorized copies.
As a result, a fair amount of work has focused on securing the Internet as a communications link. Advances in cryptography and related technologies, such as digital certificates and secure digital envelopes have significantly reduced the threat of piracy during the transmission of digital data over the Internet. For example, if a consumer wished to listen to a soundtrack at home, the soundtrack could be encrypted and then transmitted over the Internet to the consumer. The encryption would be a significant deterrent to unauthorized copiers trying to intercept the transmission.
More problematic, however, is what happens once the encrypted soundtrack arrives at the consumer's local computer. If the consumer is authorized to play the soundtrack or make a single copy of the soundtrack, for example, then the soundtrack must be decrypted at some point. When the encryption is removed, the soundtrack will be vulnerable to unauthorized copying.
Thus, there is a need for systems and methods which allow the transfer of digital data over insecure communications links and further allow the writing of this data to local media for the purpose of making authorized copies, while simultaneously preventing the unauthorized copying of that data during transfer and writing.
SUMMARY OF THE INVENTION
In accordance with the present invention, a device for securely decrypting and writing an encrypted digital file to a local recordable storage medium includes a first decryption engine, a first local memory, an encryption engine, a local storage medium, a second decryption engine, and a second local memory.
The first decryption engine incrementally decrypts the encrypted digital file, a portion at a time such that only substantially less than all of the digital file is in decrypted form at any instant. The various portions may be further preprocessed, such as being decompressed. These decrypted portions are buffered by the first local memory. The encryption engine then re-encrypts the decrypted portions from the first local memory to form an intermediate file, which is stored in the local storage medium. The second decryption engine incrementally decrypts the intermediate file, buffering the decrypted portions in the second local memory until they can be written to a recordable storage medium. Again, the incremental decryption means that substantially less than all of the digital file is in decrypted form at any instant, thus significantly reducing the risk of unauthorized copying. The use of the intermediate file is beneficial because it allows the original encrypted file to be encrypted using a strong encryption algorithm and preprocessed using computationally intensive methods which would not otherwise support the data flow rates required for certain types of recordable storage media.
In further accordance with the invention, a method for securely decrypting and writing an encrypted digital file to a recordable storage medium includes the following steps. The encrypted digital file is preprocessed and re-encrypted to form an intermediate file. Preprocessing includes incremental decryption. The intermediate file is stored to a local storage medium. The intermediate file is then incrementally decrypted and written to a recordable storage medium. Once the file is written, the intermediate file is erased.
In a second embodiment of the invention, a device for securely distributing an encrypted digital file to a recordable storage medium includes a decryption engine and a local memory. The encrypted digital file includes individually encrypted portions, and the decryption engine incrementally decrypts the encrypted portions. The local memory buffers the decrypted portions for subsequent writing to the recordable storage medium, but only stores substantially less than all of the individually encrypted portions of the digital file in decrypted form at any instant.
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Cherenson Andrew R.
Szeto Tze-Yee
Wiser Philip R.
Callahan Paul E.
De'cady Albert
Ivey James D.
Liquid Audio Inc.
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