Memory device and password storing method thereof
View Patent ↗To provide a memory device and a password storing method thereof, according to which an improved security function is realized by resourcefully designing the storage position and/or storing order of password data stored in the memory device to prevent unauthorized password acquisition. The memory device makes a determination of whether or not rewriting and/or reading of data is permitted by verification of a password, the memory device comprising a plurality of partial memory areas which store a plurality of partial bit strings that comprise a bit string of the password, and wherein the plurality of partial memory areas are located apart from each other in a memory cell array.
1. A memory device which makes a determination of whether or not rewriting and/or reading of data is permitted by verification of a password, the memory device comprising:
a plurality of partial memory areas, each of which stores a plurality of partial bit strings that comprise a bit string of the password, wherein the plurality of partial memory areas is located apart from each other in a memory cell array wherein the partial bit strings are compared to a purported password that is received.
2. The memory device according to claim 1 , wherein the plurality of partial memory areas share one of a word line and a bit line.
3. The memory device according to claim 2 , wherein, in the memory areas which share the word line or the bit line, a memory area undefined as the partial memory area is used as a data area.
4. The memory device according to claim 3 , wherein a dummy data is written into the data area.
5. The memory device according to claim 1 , comprising a first address converter circuit wherein, when the plurality of partial bit strings each receive an input of an external address in writing of the password, the first address converter circuit converts a bit allocation of the external address to output an internal address that indicates the partial memory area.
6. The memory device according to claim 5 , wherein the first address converter circuit converts a bit allocation of the internal address to a higher-order bit position than the bit allocation of the external address.
7. The memory device according to claim 6 , further comprising:
a second address converter circuit that allocates a predetermined address value to a bit string which is in a lower-bit position than the internal address output from the first address converter circuit; and
an information storage section, into which the predetermined address value is written.
8. The memory device according to claim 5 , wherein the first address converter circuit converts the bit allocation of the internal address to a different order from the bit allocation of the external address.
9. A password storing method of a memory device which makes a determination of whether or not rewriting and/or reading of data is permitted by verification of a password, the method comprising:
storing a plurality of partial bit strings that comprise a bit string of the password to be located apart from each other wherein the partial bit strings are compared to a purported password that is received.
10. The password storing method according to claim 9 , wherein said storing said plurality of partial bit strings that comprise a bit string of the password to be located apart from each other further comprises:
fixing a row address or a column address in addresses indicating memory areas, which store the partial bit strings.
11. The password storing method according to claim 10 , further comprising:
storing data into a memory area, which is undefined as a memory area for the partial bit strings in memory areas indicated by the fixed addresses.
12. The password storing method according to claim 9 , further comprising: inputting an external address for the partial bit strings when writing the password; and
converting a bit allocation of the external address to an internal address indicating a memory area in which the partial bit string is stored.
13. The password storing method according to claim 12 , wherein said converting of said bit allocations of the external addresses to internal addresses indicating a memory area in which the partial bit strings are stored includes converting bit allocations of the external addresses to a high-order bit position.
14. The password storing method according to claim 13 , further comprising:
allocating a predetermined address value to a bit string in a bit position lower than the high-order bit position.
15. The password storing method according to claim 14 , wherein said allocating of said predetermined address value includes storing the predetermined address value in rewritable manner.
16. The password storing method according to claim 12 , wherein the converting of said bit allocation of the external address to an internal address indicating a memory area in which the partial bit string is stored includes changing the order of the bit allocation of the external address.
17. A system, comprising:
a processor; a cache;
a user input component; and
a flash memory, including a memory device which makes a determination of whether or not rewriting and/or reading of data is permitted by verification of a password, the memory device comprising:
a plurality of partial memory areas each of which stores a plurality of partial bit strings that comprise a bit string of the password wherein the partial bit strings are compared to a purported password that is received, and wherein the plurality of partial memory areas are located apart from each other in a memory cell array.
18. The system as recited in claim 17 wherein the system is a portable media player.
19. The system as recited in claim 17 wherein the system is a cellular telephone.
20. The system as recited in claim 17 wherein the system is a computing device.