Detecting rewriting of stored data, using codes based on password and the stored data

• US 5,481,672 A
• Filed: 02/27/1992
• Issued: 01/02/1996
• Est. Priority Date: 02/27/1991
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Sasaki, Takayuki, Okuno, Yasuhiro, Nagashima, Masaaki, Yamakawa, Tadashi
• Primary Examiner(s): Nguyen, Hoa T.
• Application Number:
  US07/842,514
• Time in Patent Office: 1,405 Days
• Field of Search: 371/71, 371/67.1, 371/68.3, 395/575, 395/186, 395/187.01, 395/188.01, 364/927.2, 380/23, 380/4, 380/25
• US Class Current: 726/32
• CPC Class Codes: G06F 21/6209 to a single file or object, e.g. in a secure envelope, encrypted and accessed using a key, or with access control rules appended to the object itself
• CPC Class Codes: G06F 21/64 Protecting data integrity, e.g. using checksums, certificates or signatures
• CPC Class Codes: G06F 2211/007 Encryption, En-/decode, En-/decipher, En-/decypher, Scramble, (De-)compress
• CPC Class Codes: G06F 2221/2151 Time stamp

Abstract

In storing data, a first code is generated by converting a password and some predetermined portion of the data itself (e.g., all of the data itself, or a time stamp) in a predetermined procedure. The first code is then stored in correspondence to the data. Thereafter, in reading the stored data, a second code is generated by converting the password and the same predetermined portion of the stored data, using the same predetermined procedure, and the resulting second code is compared with the first code stored in correspondence to the stored data. A determination is made that a rewrite has occurred, if the two codes do not match. Subsequent data processing may be controlled in accordance with the result of this determination.

Claims

1. A method for determining whether or not a rewrite of stored data has been made, comprising the steps of:

(A) in storing newly prepared data;

inputting a password;

generating a first code by converting the input password and the newly prepared data in a predetermined procedure; and

storing the newly prepared data and the first code in correspondence thereto; and

(B) in reading out the stored data;

inputting the password;

generating a second code by converting the input password and the read out data in said predetermined procedure;

comparing the generated second code and said first code; and

determining that the rewrite of the newly prepared data has been made subsequent to storage in correspondence to the first code if the comparison result is unmatched.

2. The method according to claim 1, wherein said newly prepared data comprises a text.

3. The method according to claim 1, wherein said newly prepared data comprises a program.

4. The method according to claim 1, wherein said data to be stored and said first code corresponding thereto are stored in a same file in such manner as to be distinguished from each other.

5. The method according to claim 1, wherein said first code is stored in a file having a file name generated by adding the file name for the data corresponding to said first code with an expander.

6. A method for determining whether or not a rewrite of stored data has been made, comprising the steps of:

(A) in response to an instruction for storing newly prepared data;

storing the newly prepared data with a present time appended;

inputting a password;

extracting said present time from the stored data;

generating a first code by converting the input password and said extracted present time in a predetermined procedure; and

storing said first code in correspondence to the newly prepared and stored data; and

(B) in reading out the stored data;

inputting the password;

extracting said present time from the read out data;

generating a second code by converting the input password and the read out data in said predetermined procedure;

comparing the generated second code and said first code; and

determining that the rewrite of the newly prepared data has been made subsequent to storage in correspondence to the first code if the comparison result is unmatched.

7. The method according to claim 6, wherein said newly prepared data comprises a text.

8. The method according to claim 6, wherein said newly prepared data comprises a program.

9. The method according to claim 6, wherein said first code is stored in a file having a file name generated by adding the file name for the data corresponding to said first code with an expander.

10. A method for determining whether or not a rewrite of stored data has been made, comprising the steps of:

(A) in response to an instruction for storing newly prepared data;

storing the newly prepared data with a first present time appended;

inputting a password;

extracting said first present time from the stored data;

generating a first code by converting the input password and said extracted first present time in a predetermined procedure;

restoring said newly prepared data, accompanied by and distinguished from the generated first code and a second present time; and

changing the second present time stored with the restored data to said first present time; and

(B) in reading out the stored data;

inputting the password;

extracting said first present time from the read out data;

generating a second code by converting the input password and said extracted first present time in said predetermined procedure;

comparing the generated second code and said first code; and

determining that the rewrite of the newly prepared data has been made subsequent to storage in correspondence to the first code if the comparison result is unmatched.

11. The method according to claim 10, wherein said newly prepared data comprises a text.

12. The method according to claim 10, wherein said newly prepared data comprises a program.

13. A method for determining whether or not a rewrite of stored data has been made, comprising the steps of:

(A) in response to an instruction for storing newly prepared data;

storing the newly prepared data with a first present time appended;

inputting a password;

inputting time information;

generating a first code by converting the input password and the input time information in a predetermined procedure;

restoring said newly prepared data, accompanied by and distinguished from the generated first code and a second present time; and

changing the second present time stored with the restored data to said time information; and

(B) in reading out the stored data;

inputting the password;

extracting said time information from the read out data;

generating a second code by converting the input password and the extracted time information in said predetermined procedure;

comparing the generated second code and said first code; and

determining that the rewrite of the newly prepared data has been made subsequent to storage in correspondence to the first code if the comparison result is unmatched.

14. The method according to claim 13, wherein said newly prepared data comprises a text.

15. The method according to claim 13, wherein said newly prepared data comprises a program.

16. A method for determining whether or not a rewrite of stored data has been made, comprising the steps of:

(A) in storing newly prepared data;

determining a user;

generating a first code by converting the information corresponding to the determined user and the newly prepared data in a predetermined procedure; and

storing the newly prepared data and the first code in correspondence thereto; and

(B) in reading out the stored data;

determining the user;

generating a second code by converting the information corresponding to the determined user and the read out data in said predetermined procedure;

comparing the generated second code and said first code; and

determining that the rewrite of the newly prepared data has been made subsequent to storage in correspondence to the first code if the comparison result is unmatched.

17. The method according to claim 16, wherein said newly prepared data comprises a text.

18. The method according to claim 16 wherein said newly prepared data comprises a program.

19. The method according to claim 16, wherein said first code is stored in a file having a file name generated by adding the file name for the data corresponding to said first code with an expander.

20. The method according to claim 16, wherein the information corresponding to said user comprises a user name.

21. The method according to claim 16, wherein the information corresponding to said user comprises a log-in directory correspondent to a plurality of users.

22. A method for determining whether or not a rewrite of stored data has been made and processing the stored data in accordance with a result of such determination, comprising the steps of:

(A) in storing newly prepared data;

inputting a password;

generating a first code by converting the input password and a predetermined portion of the newly prepared data in a predetermined procedure; and

storing the newly prepared data and the first code in correspondence thereto;

(B) in processing the stored data;

inputting the password;

generating a second code by reading out the stored data and converting the input password and said predetermined portion of the read out data in said predetermined procedure;

comparing the generated second code and said first code; and

processing the read out data if the comparison result is matched, and prohibiting the processing if the comparison result is unmatched.

23. The method according to claim 22, wherein said predetermined portion of the newly prepared data is the newly prepared data itself.

24. The method according to claim 22, wherein said password comprises information corresponding to the user.

25. The method according to claim 22, wherein said newly prepared data comprises a text.

26. The method according to claim 22, wherein said newly prepared data comprises a program.

27. The method according to claim 22, further comprising the step of second processing the read out data when the comparison result is unmatched, wherein the second processing is different from the processing when the comparison result is matched.