Encapsulation of public key cryptography standard number 7...

Details Encapsulation of public key cryptography standard number 7... Encapsulation of public key cryptography standard number 7...

1998-08-28

2001-03-20

Peeso, Thomas R. (Department: 2767)

Electrical computers and digital processing systems: support

System access control based on user identification by...

C380S259000, C380S260000, C380S283000

Reexamination Certificate

active

06205549

ABSTRACT:

BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention is related to the field of providing secured access to documents, more specifically, the method and apparatus of the present invention is related to utilizing a Public Key Cryptography Standard number 7 (PKCS#7) object to provide recipients secured access to encrypted data.
(2) Related Art
Portable document format (PDF) is a file format utilized to represent a document in a manner independent of the application software, hardware and operating system used to create it. A document is converted into a PDF document/data by a PDF writer. A PDF document/data contains one or more pages, each page in the document containing a combination of text, graphics and images and may also contain information such as hypertext links, sound and movies. A user may view and edit a PDF document/data through a graphical user interface (GUI) provided by a PDF viewer application. To access a secured PDF document/data, a user must provide the PDF viewer application with a valid password.
Public Key Cryptography Standard number 7 (PKCS#7) is an object specification from RSA Data Securities, Inc. of San Mateo, Calif. A PKCS#7 object is binary encoded and contains various attributes. When used to encrypt data, a PKCS#7 object is designed to encapsulate a single encrypted copy of the data to be encrypted. A PKCS#7 object also contains a list of recipients for access to the data. For each recipient, an encrypted key that may be used to decrypt the encrypted access information is provided. The key is encrypted using the recipient's public key.
The currently available method of providing a user secured access to a PDF document/data by use of a password is disadvantageous in that passwords must be available to all recipients, rather than distribution being designed based around a recipient list that uses public-key private key technology. PKCS#7 standard for providing secured access to a document is advantageous in that the PKCS#7 provides the use of public-key private key technology and thereby obviates the use of passwords. However, PKCS#7 defines the data to be encrypted as being encapsulated by a PKCS#7 object.
It is therefore desirable to have a method and apparatus to incorporate the advantages found in PKCS#7 standard into providing secured access to a PDF document/data in a PDF file and overcome the disadvantages of the PKCS#7's forced document encapsulation.
BRIEF SUMMARY OF THE INVENTION
In the present invention, secured access to a document is controlled using a Public Key Cryptography Standard number 7 (PKCS#7) object that is embedded into the document. The PKCS#7 object contains a recipient list and access rights for a recipient. One embodiment of the current invention is its use in documents with a format specification defined by the Portable Document Format (PDF) specification. The PDF format specification is well known in the art.
Currently, PKCS#7 is defined for an ‘enveloped data’ that is encapsulated in the PKCS#7 object to contain the document data. In the invention, the ‘enveloped data’ contains access information that is used to access the remainder of the document into which the PKCS#7 object is encapsulated.
The access information can be decrypted by all recipients in the PKCS#7 recipient list. If a recipient listed in the recipient list attempts to access data in a document, the access information is decrypted using the recipient's private key. The access information is used to obtain an access key that is used to decrypt data in the document.


REFERENCES:
RSA Data Security, Inc. Public-Key Cryptography Standards (PKCS) “PKCS #7: Cryptographic Message Syntax Standard”.

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