One-time programmable memories for key storage
First Claim
1. An integrated circuit comprising:
- an obfuscation circuit;
a memory coupled to the obfuscation circuit;
a reverse obfuscation circuit coupled to the memory;
a first circuit coupled to the memory;
a write enable line coupling the first circuit to the memory;
a second circuit coupled to the first circuit, wherein the second circuit is configured to disable the first circuit after a key is written to the memory; and
a third circuit configured to;
prevent the memory from outputting the key written to the memory when the first circuit is enabled; and
allow the memory to output the key written to the memory when the first circuit is disabled.
1 Assignment
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Accused Products
Abstract
Circuits, methods, and apparatus that store and prevent modification or erasure of stored encoding keys, serial identification numbers, or other information. An encoding key stored with an embodiment of the present invention may be used to decode a configuration bitstream on an integrated circuit, such as an FPGA. A serial number may be used to track or authenticate an integrated circuit. Embodiments of the present invention store this information in a memory such as an SRAM, DRAM, EPROM, EEPROM, flash, fuse array, or other type of memory. In order to prevent its erasure or modification, write enable circuitry for the memory is then permanently disabled, and if the memory is volatile, a continuous power supply is provided. Further refinements verify that the write enable circuitry has been disabled before allowing the device to be configured or to be operable.
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Citations
20 Claims
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1. An integrated circuit comprising:
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an obfuscation circuit; a memory coupled to the obfuscation circuit; a reverse obfuscation circuit coupled to the memory; a first circuit coupled to the memory; a write enable line coupling the first circuit to the memory; a second circuit coupled to the first circuit, wherein the second circuit is configured to disable the first circuit after a key is written to the memory; and a third circuit configured to; prevent the memory from outputting the key written to the memory when the first circuit is enabled; and allow the memory to output the key written to the memory when the first circuit is disabled. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method comprising:
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writing a key to a memory, wherein; a first circuitry is coupled to the memory by a write enable line, and the first circuitry is enabled during the writing of the key to the memory; preventing the memory from outputting the key written to the memory when the first circuitry is enabled; allowing the memory to output the key written to the memory when the first circuitry is disabled; and disabling the first circuitry using second circuitry after the key is written to the memory. - View Dependent Claims (8, 9, 10, 11, 12, 13)
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14. An integrated circuit comprising:
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a memory; input circuitry configured to write a key to the memory; first circuitry coupled to the memory by a write enable line, wherein the first circuitry is enabled during the writing of the key to the memory; control circuitry configured to; prevent the memory from outputting the key written to the memory when the first circuitry is enabled; and allow the memory to output the key written to the memory when the first circuitry is disabled; and second circuitry coupled to the first circuitry, wherein the first circuitry is configured to disable the first circuitry using after the key is written to the memory. - View Dependent Claims (15, 16, 17, 18, 19, 20)
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Specification