Initially , the details of the algorithm were kept secret â '' proprietary to RSA Security â '' but on 29th January , 1996 , source code for RC2 was anonymously posted to the Internet on the Usenet forum , sci . Initially , the details of the algorithm were kept secret -- proprietary to RSA Security -- but on 29th January , 1996 , source code for RC2 was anonymously posted to the Internet on the Usenet forum , sci .