The RSA algorithm can be used for a kind of unforgeable digital signature. In this application, the secret key is used to encrypt a message, which can then itself be decrypted by anyone possessing the public key. Digital signatures can play a role in many activities that do not require secrecy but require sender authentication and guaranteed message integrity. Because it offers the possibility of true privacy and secrecy, public key cryptography has become a cause celebre among many computer users. Nevertheless, the RSA algorithm, developed in 1977, remained the stuff of academic curiosity for nearly 20 years and did not enjoy widespread use. Three factors combined to delay the spread of public key cryptography: the speed disparity between low-cost and high-cost computers, intellectual property law, and the US government's export control laws, which remain a problem to this day.