Electronically verified digital signature and document delivery system and method

• US 7,082,538 B2
• Filed: 10/03/2001
• Issued: 07/25/2006
• Est. Priority Date: 10/03/2000
• Status: Expired due to Term

• Current Assignee: Upland Software, Inc.
• Original Assignee: Omtool Limited (Upland Software, Inc.)
• Inventors: Benson, Glenn, Bouchard, Thaddeus
• Primary Examiner(s): Barron, Jr., Gilberto
• Assistant Examiner(s): PERUNGAVOOR, VENKATANARAY
• Application Number:
  US09/970,147
• Publication Number:
  US 20020091928A1
• Time in Patent Office: 1,756 Days
• Field of Search: 713/181, 713/178
• US Class Current: 713/181
• CPC Class Codes: G06F 2221/2151 Time stamp
• CPC Class Codes: H04L 2209/56 Financial cryptography, e.g. electronic payment or e-cash
• CPC Class Codes: H04L 2209/60 Digital content management, e.g. content distribution
• CPC Class Codes: H04L 9/3247 involving digital signatures
• CPC Class Codes: H04L 9/3297 involving time stamps, e.g. generation of time stamps

Abstract

The secure messaging system of the invention encrypts an electronic document using a symmetric key and transmits the encrypted document and related message parameters to a recipient whose identity is then authenticated by a web server. The web server dynamically regenerates the symmetric key from a hidden key and from the message parameters accompanying the encrypted document, and thus avoids having to maintain a central repository of encrypted documents as required by typical “post and pick-up” encrypted messaging systems. Further, an audit trail produced while practicing the invention provides timestamped message digest data for a plurality of time intervals, where the message digests for adjacent time intervals are computationally linked together. The audit trail effectively enables timestamped message digest data to verify not only the existence of a document during a first time interval, but also to verify the existence of documents encountered in a prior time interval.

Claims

1. A method of preventing the repudiation of digitally-signed electronic documents, the method comprising:

receiving a plurality of electronic documents during a first and second time interval;

forming a message digest for each of the plurality of electronic documents;

forming a first super-message digest derived at least in part from each of the message digests received during the first time interval;

forming a second super-message digest derived at least in part from each of the message digests received during the second time interval and from the first super-message digest;

transmitting the second super-message digest to a timestamp authority and receiving a timestamp therefrom; and

recording each of the message digests, first and second super-message digests, and timestamp in an audit log,

wherein at least one of the plurality of electronic documents corresponds to a file attachment in an electronic mail message.

2. A method of preventing the repudiation of digitally-signed electronic documents, the method comprising:

receiving a plurality of electronic documents during a first and second time interval;

forming a message digest for each of the plurality of electronic documents;

forming a first super-message digest derived at least in part from each of the message digests received during the first time interval;

forming a second super-message digest derived at least in part from each of the message digests received during the second time interval and from the first super-message digest;

transmitting the second super-message digest to a timestamp authority and receiving a timestamp therefrom; and

recording each of the message digests, first and second super-message digests, and timestamp in an audit log,

wherein the first and second time intervals are pre-determined.

3. A method of preventing the repudiation of digitally-signed electronic documents, the method comprising:

receiving a plurality of electronic documents during a first and second time interval;

forming a message digest for each of the plurality of electronic documents;

forming a first super-message digest derived at least in part from each of the message digests received during the first time interval;

forming a second super-message digest derived at least in part from each of the message digests received during the second time interval and from the first super-message digest;

transmitting the second super-message digest to a timestamp authority and receiving a timestamp therefrom; and

recording each of the message digests, first and second super-message digests, and timestamp in an audit log,

wherein the duration of the first and second time intervals are dynamically determined from a number of electronic documents anticipated during a particular time of day.

4. A method of preventing the repudiation of digitally-signed electronic documents, the method comprising:

receiving a plurality of electronic documents during a first and second time interval;

forming a message digest for each of the plurality of electronic documents;

forming a first super-message digest derived at least in part from each of the message digests received during the first time interval;

forming a second super-message digest derived at least in part from each of the message digests received during the second time interval and from the first super-message digest;

transmitting the second super-message digest to a timestamp authority and receiving a timestamp therefrom;

recording each of the message digests, first and second super-message digests, and timestamp in an audit log; and

recording a timestamp associated with the first super-message digest in the audit log,

wherein the second super-message digest is further derived from the timestamp associated with the first super-message digest.

5. The method of claim 4 wherein the second super-message digest is further derived from the timestamp associated with a prior super-message digest.

6. A computer-readable medium comprising code that prevents the repudiation of digitally-signed electronic documents, the code performing the steps of:

receiving a plurality of electronic documents during a first and second time interval;

forming a message digest for each of the plurality of electronic documents;

forming a first super-message digest derived at least in part from each of the message digests received during the first time interval;

forming a second super-message digest derived at least in part from each of the message digests received during the second time interval and from the first super-message digest;

transmitting the second super-message digest to a timestamp authority and receiving a timestamp therefrom; and

recording each of the message digests, first and second super-message digests, and timestamp in an audit log,

wherein at least one of the plurality of electronic documents corresponds to a file attachment in an electronic mail message.

7. A computer-readable medium comprising code that prevents the repudiation of digitally-signed electronic documents, the code performing the steps of:

receiving a plurality of electronic documents during a first and second time interval;

forming a message digest for each of the plurality of electronic documents;

forming a first super-message digest derived at least in part from each of the message digests received during the first time interval;

forming a second super-message digest derived at least in part from each of the message digests received during the second time interval and from the first super-message digest;

transmitting the second super-message digest to a timestamp authority and receiving a timestamp therefrom; and

recording each of the message digests, first and second super-message digests, and timestamp in an audit log,

wherein the first and second time intervals are pre-determined.

8. A computer-readable medium comprising code that prevents the repudiation of digitally-signed electronic documents, the code performing the steps of:

receiving a plurality of electronic documents during a first and second time interval;

forming a message digest for each of the plurality of electronic documents;

forming a first super-message digest derived at least in part from each of the message digests received during the first time interval;

forming a second super-message digest derived at least in part from each of the message digests received during the second time interval and from the first super-message digest;

transmitting the second super-message digest to a timestamp authority and receiving a timestamp therefrom; and

recording each of the message digests, first and second super-message digests, and timestamp in an audit log,

wherein the duration of the first and second time intervals are dynamically determined from a number of electronic documents anticipated during a particular time of day.

9. A computer-readable medium comprising code that prevents the repudiation of digitally-signed electronic documents, the code performing the steps of:

receiving a plurality of electronic documents during a first and second time interval;

forming a message digest for each of the plurality of electronic documents;

forming a first super-message digest derived at least in part from each of the message digests received during the first time interval;

forming a second super-message digest derived at least in part from each of the message digests received during the second time interval and from the first super-message digest;

transmitting the second super-message digest to a timestamp authority and receiving a timestamp therefrom;

recording each of the message digests, first and second super-message digests, and timestamp in an audit log; and

recording a timestamp associated with the first super-message digest in the audit log,

wherein the second super-message digest is further derived from the timestamp associated with the first super-message digest.

10. The computer-readable medium of claim 9 wherein the second super-message digest is further derived from the timestamp associated with a prior super-message digest.