A method of passing a cryptographic key that allows recovery of the key by a third party by generating a first random number by a first user; generating "key1" by the first user; generating a second random number "k2a" by the first user; computing "y1" by the first user; computing "y2" by the first user;...http://www.google.de/patents/US6724893?utm_source=gb-gplus-sharePatent US6724893 - Method of passing a cryptographic key that allows third party access to the key
