Prof. Dr. Claus Peter Schnorr
61231 Bad Nauheim
Frankfurter Strasse 81
Germany
March 27, 1998
PHONE +49 603284450
FAX +49 6979828841
email schnorr@cs.uni-frankfurt.de

via fax +617 687 7213 and mail
Burt Kaliski, chair, IEEE P1363
RSA Laboratories
20 Crosby Drive
Bedford, Ma 01730


RE: Patents and Trademarks for IEEE P1363 Working Group
       Your letter of March 18, 1998

Dear Burt:

This letter supersedes my letter of November 9, 1997. The following patents have been issued to me:

EP-Patent 0384475, filed on February 22, 1990
and issued in 11 European countries,
U.S. Patent 4995082, filed on February 23, 1990,
JP-Patent 2666191, filed on February 23, 1990.

These patents are equivalent except that the European and the Japanese Patent have a broader claim coverage than the U.S. registration.

From studied review it is evident that the Nyberg-Rueppel signature generation and verification (DLSP-NR and DLVP-NR) and the NIST Digital Signature Algorithm (DLSP-DSA and DLVP-DSA) involve the discrete log signatures using subgroups of the integers modulo a prime p that are of a prime order q as well as discrete log signatures using elliptic curves.

The above mentioned patents apply to various implementations of discrete log signatures of that sorts and hence covers the use of Nyberg-Rueppel and DSA signatures in these instances.

I have licensed RSA Data Security, Inc. as the exclusive -- except for Siemens AG -- licensing authority of my patents. Siemens AG has a non-exclusive license of my patents including the right of sublicensing.

Licenses are available on a reasonable and non-discriminatory basis. License terms may be obtained by contacting either the Manager of Intellectual Property, James Ting at RSA or Mr. Wehr at Siemens AG:

James Ting
RSA-Laboratories
100 Marine Parkway
USA 81359
FAX 650 595 5198
phone 650 595 8782

Herr Wehr
Siemens AG
Rechtsabteilung 2
Hofmannstr. 51
München
Germany
FAX +89 722 25211
phone +89 722 62793

Sincerely,


Claus P. Schnorr

PS.:Enclosed is a study on the coverage of the DSA by EP-Patent 0384475.