Granted Patent
Utility
US 4,947,430 · App. 07/123,703
Undeniable signature systems
Inventor:
David Chaum
Patented Case
View Patent ↗
Granted: Aug 7, 1990
Filed: Nov 23, 1987
Inventor
David Chaum
This patent predates the USPTO's electronic file wrapper — prosecution documents from this era exist only in the Patent Office's paper records. A certified copy of the file history can be ordered from the USPTO's paper archives.