Method for retrieving secure information from a database

• US 5,473,687 A
• Filed: 12/29/1993
• Issued: 12/05/1995
• Est. Priority Date: 12/29/1993
• Status: Expired due to Term

• Current Assignee: Harmony Logic Systems LLC (Intellectual Ventures LLC)
• Original Assignee: Infosafe Systems Incorporated
• Inventors: Nagel, Robert H., Lipscomb, Thomas H.
• Primary Examiner(s): Cangialosi, Salvatore
• Application Number:
  US08/174,741
• Time in Patent Office: 706 Days
• Field of Search: 380/4, 380/46
• US Class Current: 705/51
• 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 21/80 in storage media based on magnetic or optical technology, e.g. disks with sectors preventing unauthorised reproduction or copying of disc-type recordable media G11B20/00
• CPC Class Codes: G06F 2211/007 Encryption, En-/decode, En-/decipher, En-/decypher, Scramble, (De-)compress
• CPC Class Codes: G11B 20/00666 involving a step of erasing or nullifying data, e.g. data being overwritten with a random string

Abstract

A system for retrieving a packet of informational digital data which is stored on a secure storage medium. The informational data packet (IDP) is read from the secure storage medium and then expanded in length to form a sequence of digital data which is so large as to be inconvenient for permanent storage.

Claims

1. A method of retrieving a packet of informational digital data which is stored in encrypted form, said method comprising the steps of:

(a) retrieving the stored informational data packet (IDP);

(b) decrypting the IDP into a first sequence of digital data;

(c) expanding the first sequence of digital data into a second sequence of digital data which is so large as to be inconvenient for permanent storage, said expanding step including the step of embedding said first sequence of digital data in a series of pseudorandom digital data which is substantially equal to 1-5 megabytes or more in length, such that said second sequence is substantially equal to 1.5 megabytes or more in length and is not compressible;

(d) storing said second sequence of digital data;

(e) retrieving the stored second sequence of digital data; and

(f) extracting the IDP from said second sequence.

2. The method defined in claim 1, wherein said first sequence of digital data is embedded in a different way during each successive execution of said expanding step.

3. The method defined in claim 1, wherein said embedding step includes the steps of obtaining a key and a random number generating algorithm which requires a key, and thereafter executing said random number generating algorithm with said key to produce said pseudorandom digital data.

4. The method defined in claim 3, wherein said key is obtained from an external source.

5. The method defined in claim 3, wherein a plurality of IDPs are stored in encrypted form on a storage medium having a file directory stored thereon indicating the identity, location and length of each IDP, and wherein said step of obtaining said key includes the steps of reading said file directory and determining said key from information contained therein.

6. The method defined in claim 5, wherein said key is determined from information contained in said file directory relating to the IDP to be decrypted.

7. The method defined in claim 3, wherein said information data packet (IDP) is stored on a storage medium and wherein said key is obtained from said storage medium.

8. The method defined in claim 3, wherein said information data packet (IDP) is stored on a storage medium with a file directory which contains the identity, location and length of said IDP, and wherein said key is obtained from said file directory.

9. The method defined in claim 3, wherein said random number generating algorithm is the Data Encryption Standard (DES) algorithm.

10. The method defined in claim 3, wherein said random number generating algorithm is formed by a linear feedback shift register.

11. The method defined in claim 1, wherein said information data packet (IDP) is stored on a storage medium in a plurality of blocks each of a prescribed length, and wherein said packet is combined, block by block, with said pseudorandom digital data to expand the bit length of each block such that the total length of all expanded blocks of data is substantially equal to 1.5 megabytes or more.

12. The method defined in claim 1, wherein said length of said second sequence is greater than the largest hand-held, removable storage medium.

13. The method defined in claim 1, wherein said embedding step is unique each time said packet is expanded.

14. The method defined in claim 1, wherein the bit length of said pseudorandom digital data is equal to the bit length of said second sequence.

15. The method defined in claim 1, wherein the bit length of said second sequence is equal to at least twice the bit length of said first sequence.

16. The method defined in claim 14, wherein the bit length of said second sequence is equal to at least said twice the bit length of said first sequence plus two binary digits.

17. The method defined in claim 1, wherein said step of extracting the IDP from said second sequence includes the steps of:

(e) producing said pseudorandom digital data; and

(f) combining said pseudorandom digital data with said second sequence to produce said information data packet.

18. The method defined in claim 17, wherein said combining step (f) includes the steps of:

(1) logically combining said pseudorandom data with said second sequence by exclusive-or to produce a result; and

(2) scanning said result for binary one'"'"'s.