06263438 is referenced by 87 patents and cites 73 patents.

The invention relates devices and methods for creating a cryptographically assured timestamp that can be verified by a party that was not present during the creation of the timestamp. The timestamp is applied to physical documents, and other substrates capable of receiving an optically detectable mark, that are to be transmitted to temporally or spatially distant recipients.

Title
Method and apparatus for secure document timestamping
Application Number
9/149024
Publication Number
6263438 (B1)
Application Date
September 8, 1998
Publication Date
July 17, 2001
Inventor
James A Jorasch
Stamford
CT, US
Bruce Schneier
Oak Park
IL, US
Jay S Walker
Ridgefield
CT, US
Agent
Nandu A Talwalkar
US
Dean Alderucci
US
Assignee
Walker Digital
CT, US
IPC
G06F 1/26
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