Method for strongly encrypting .ZIP files

• US 9,098,721 B2
• Filed: 06/05/2012
• Issued: 08/04/2015
• Est. Priority Date: 07/16/2003
• Status: Active Grant

• Current Assignee: PKWARE, Inc. (PKW Holdings, Inc.)
• Original Assignee: PKWARE, Inc. (PKW Holdings, Inc.)
• Inventors: Peterson, James C.
• Primary Examiner(s): Dinh, Minh
• Application Number:
  US13/489,011
• Publication Number:
  US 20120284536A1
• Time in Patent Office: 1,155 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: G06F 16/1744 using compression, e.g. sparse files
• 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 21/6218 to a system of files or objects, e.g. local or distributed file system or database
• CPC Class Codes: G06F 2221/2107 File encryption
• CPC Class Codes: G06F 2221/2153 Using hardware token as a secondary aspect
• CPC Class Codes: H04L 2209/30 Compression, e.g. Merkle-Damgard construction
• CPC Class Codes: H04L 9/0819 Key transport or distribution, i.e. key establishment techniques where one party creates or otherwise obtains a secret value, and securely transfers it to the other(s) network architectures or network communication protocols for key distribution in a packet data network H04L63/062
• CPC Class Codes: H04L 9/088 Usage controlling of secret information, e.g. techniques for restricting cryptographic keys to pre-authorized uses, different access levels, validity of crypto-period, different key- or password length, or different strong and weak cryptographic algorithms network architectures or network communication protocols for using time-dependent keys in a packet data network H04L63/068

Abstract

The present invention provides a method of integrating existing strong encryption methods into the processing of a .ZIP file to provide a highly secure data container which provides flexibility in the use of symmetric and asymmetric encryption technology. The present invention adapts the well established .ZIP file format to support higher levels of security and multiple methods of data encryption and key management, thereby producing a highly secure and flexible digital container for electronically storing and transferring confidential data.

Claims

1. A method of placing data in a .ZIP file format data container on a computer, said method including:

receiving a data file at an application on a computer, wherein said data file has been retrieved from an electronic computer data storage by said application;

compressing said data file to form a compressed data file using said application before encrypting said data file;

encrypting said compressed data file to form an encrypted data file, wherein said encrypting uses symmetric encryption using a symmetric key having a symmetric key bit length selected by a user, wherein said symmetric key bit length is one of a plurality of available symmetric key bit lengths that are selectable by said user using said application;

placing said encrypted data file in a data container using said application on said computer,

wherein said data container is constructed in accordance with the .ZIP file format,

wherein said data container includes an electronic indication that said encrypted data file is encrypted,

wherein said data container includes a second electronic indication that said encrypted data file was encrypted with an encryption method using said symmetric key bit length selected by said user,

wherein said data container includes an electronic extra field, wherein said extra field includes an electronic indication of the symmetric key bit length of the symmetric key selected by said user that was employed in encrypting said encrypted data file;

storing said data container constructed in accordance with the .ZIP file format; and

setting a flag in a decryption header of the encrypted file in the data container indicating that both a password and recipient list are required to decrypt the file and that a random number used to generate the symmetric key is encrypted twice by two separate keys.

2. The method of claim 1 wherein said symmetric key bit length has a length of at least 192 bits.

3. The method of claim 1 wherein said symmetric key bit length has a length of at least 256 bits.

4. The method of claim 1 wherein said encrypting employs an Advanced Encryption Standard (AES)-type encryption algorithm.

5. The method of claim 1 wherein said encrypting employs a Triple Data Encryption Standard (3DES)-type encryption algorithm.

6. The method of claim 1 wherein said compressing employs a Lempel-Ziv (LZ)-type data compression algorithm.

7. The method of claim 1 wherein said compressing employs a Deflate-type data compression algorithm.

8. The method of claim 1 wherein said compressing employs a Burrows-Wheeler Transform (BWT)-type data compression algorithm.

17. The method of claim 1 wherein said symmetric key bit length has a length of at least 128 bits.

9. A system for placing data in a .ZIP file format data container on a computer, said system including:

an electronic computer data storage;

a processor executing computer instructions implementing an application, said application configured to;

receive a data file, wherein said data file has been retrieved from said electronic computer data storage by said application;

compress said data file to form a compressed data file before encrypting said data file;

encrypt said compressed data file to form an encrypted data file, wherein said encrypting uses symmetric encryption using a symmetric key having a symmetric key bit length selected by a user, wherein said symmetric key bit length is one of a plurality of available symmetric key bit lengths that are selectable by said user using said application;

place said encrypted data file in a data container,

wherein said data container is constructed in accordance with the .ZIP file format,

wherein said data container includes an electronic indication that said encrypted data file is encrypted,

wherein said data container includes a second electronic indication that said encrypted data file was encrypted with an encryption method using said symmetric key bit length selected by said user,

wherein said data container includes an electronic extra field, wherein said extra field includes an electronic indication of the symmetric key bit length of the symmetric key selected by said user that was employed in encrypting said encrypted data file;

store said data container constructed in accordance with the .ZIP file format in said electronic computer data storage; and

set a flag in a decryption header of the encrypted file in the data container indicating that both a password and recipient list are required to decrypt the file and that a random number used to generate the symmetric key is encrypted twice by two separate keys.

10. The system of claim 9 wherein said symmetric key bit length has a length of at least 192 bits.

11. The system of claim 9 wherein said symmetric key bit length has a length of at least 256 bits.

12. The system of claim 9 wherein said encrypting employs an Advanced Encryption Standard (AES)-type encryption algorithm.

13. The system of claim 9 wherein said encrypting employs a Triple Data Encryption Standard (3DES)-type encryption algorithm.

14. The system of claim 9 wherein said compressing employs a Lempel-Ziv (LZ)-type data compression algorithm.

15. The system of claim 9 wherein said compressing employs a Deflate-type data compression algorithm.

16. The system of claim 9 wherein said compressing employs a Burrows-Wheeler Transform (BWT)-type data compression algorithm.

18. The system of claim 9 wherein said symmetric key bit length has a length of at least 128 bits.