Static information storage and retrieval – Floating gate – Data security
Reexamination Certificate
2000-05-18
2001-07-24
Ho, Hoai V. (Department: 2818)
Static information storage and retrieval
Floating gate
Data security
Reexamination Certificate
active
06266271
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a nonvolatile semiconductor memory, such as flash memory, for preventing the unauthorized reproduction of data stored in a main storage region.
2. Description of the Related Art
Flash memory, which is nonvolatile semiconductor memory, is able to write (program) and erase data electrically, and is widely used because stored data is not lost even when the power is turned OFF. For example, it is becoming popular as a memory card for storing music data distributed for a fee via the Internet. Further, it has also come into widespread use as memory for storing data and programs specific to cellular telephones and other compact information terminals.
To prevent the unauthorized copying of music data, and specified data or programs stored in the above-mentioned flash memory, and to prevent the use of flash memory in illegally obtained data equipment, an unauthorized copying prevention function, and an unauthorized use prevention function are required. These functions are achieved, for example, by providing inside flash memory a hidden storage region for storing special data and a key code, in addition to a main storage region for storing ordinary data. This hidden storage region is a one-time programmable memory, and is a storage region that cannot be used by ordinary users.
FIG. 1
is a diagram for explaining unauthorized copying prevention, and unauthorized copying. In flash memory, there are provided a main storage region
1
for storing ordinary data, and a hidden storage region
2
for storing special data, and furthermore, there is provided a write protect circuit
3
, which prohibits the rewriting of stored data inside a hidden storage region
2
. In addition thereto, flash memory is equipped with circuits required for writing (programming), erasing, and reading.
Now, let us assume that flash memory A, B is memory obtained legally on the market, and that flash memory X is memory that has been obtained illegally. In the flash memory A, B marketed legally, key codes A, B have been written to the respective hidden storage regions
2
, and the respective write protect circuits
3
are in the protect mode, which prohibits rewriting. Now then, for example, when predetermined music data is stored in flash memory A, data A is encrypted in accordance with key code A, and this encrypted data A is stored in the main storage region
1
. Then, when music data A is played back, data A is read out, decoded by key code A, and the decoded music data thereof is played.
Conversely, when music data A is illegally copied to flash memory B, key code A-encrypted data A is copied inside the main storage region
1
of flash memory B. Consequently, when an attempt is made to play back this illegally copied music data A, the original music data A cannot be acquired by decoding by key code B inside the hidden storage region
2
of flash memory B, and in the end, cannot be played back.
The same technique can be used to prevent the illegal use of information by unauthorized copying in the case of predetermined data or programs instead of music data.
However, if flash memory X of a state, wherein a key code is not written into the hidden storage region
2
at shipment, is illegally placed on the black market, the above-mentioned unauthorized copying prevention function is lost. That is, by storing in respective regions
1
,
2
of an illegally obtained flash memory X both key code A of inside a hidden storage region
2
, and data A encrypted inside a main storage region
1
of a flash memory A, in which is stored legally encrypted data A, it is possible to illegally copy and illegally use data A.
Therefore, there is need for a nonvolatile semiconductor memory that is capable of preventing the unauthorized copying of data, and the unauthorized use of data in line therewith, even when same is illegally sold on the black market as-is without being programmed with a with a special code in the hidden storage region
2
as described above.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a nonvolatile semiconductor memory capable of preventing the unauthorized copying of data.
A further object of the present invention is to provide a nonvolatile semiconductor memory capable of preventing the unauthorized copying of data, and the unauthorized use of data in line therewith, even when this nonvolatile semiconductor memory is illegally sold on the black market.
To achieve the above-mentioned objects, one aspect of the present invention is a nonvolatile semiconductor memory having, in addition to a main storage region for storing ordinary data, a hidden storage region for storing a special code for preventing unauthorized copying, and this hidden storage region is in a read enabled state at the time of a write protected state, and is in a read prohibited state at a time when there is no write protected state. Therefore, a hidden storage region can be read out only after a semiconductor memory vendor stores a special code in a hidden storage region, and sets the hidden storage region to a write protected state. And the method for changing to this write protected state is a secret to everyone other than the vendor. As a result thereof, even if a semiconductor memory, for which a special code is not stored in a hidden storage region, is illegally obtained on the black market, since hidden storage region readout is still prohibited, illegally copied data cannot be used, consequently preventing unauthorized copying.
To achieve the above-mentioned objects, another aspect of the present invention is a nonvolatile semiconductor memory constituted such that, in addition to a main storage region for storing ordinary data, it has a hidden storage region for storing a special code for preventing unauthorized copying, and this hidden storage region is constituted to be a read enabled state only after the above-mentioned special code has been stored. Consequently, a hidden storage region becomes capable of being read only after a semiconductor memory vendor stores a special code in the hidden storage region, thus preventing unauthorized copying the same as hereinabove.
The above-mentioned special code is, for example, either an encryption code for encrypting the data of a main storage region, or a code for generating this encryption code. There are also cases in which a special code is a recognition code for matching up the semiconductor memory thereof with information equipment capable of using same. In accordance with using this special code, it is possible to constitute the nonvolatile semiconductor memory such that even if data inside a main storage region is copied to another memory illegally, the copied data thereof cannot be utilized.
To achieve the above-mentioned objects, one aspect of the present invention is a nonvolatile semiconductor memory for electrically writing and reading data, comprising: a main storage region for storing ordinary data; a hidden storage region for storing a special code for preventing unauthorized copying; and a write protect circuit for setting the hidden storage region in a write protected state, wherein the hidden storage region is in a read enabled state at the time of a write protected state, and is in a read prohibited state when not in the write protected state.
A preferred embodiment of the above-mentioned invention further comprises a command decoder for decoding a write and a read command from outside, and for generating a respective internal write signal and internal read signal for the hidden storage region, and the command decoder is prohibited from generating the internal read signal when the write protect circuit is not in the write protected state, and is enabled for generating the internal read signal at the time of the write protected state.
Another aspect of the present invention is a nonvolatile semiconductor memory for electrically writing and reading data, comprising: a main storage region for storing ordinary data, and a hidden storage region for stor
Arent Fox Kintner & Plotkin & Kahn, PLLC
Fujitisu Limited
Ho Hoai V.
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