Abstract: A receiver operating in a broadcast system is disclosed that allows a broadcaster to provide multiple tiers of subscription services. By a receiver that can operating at different tiers, a subscriber has the option of listening to fewer (or no) commercials, e.g., by paying a higher fee, or listening to more commercials, e.g., by paying a lower or no fee. Commercials can be demographically targeted, cannot be skipped, and can be audited for billing purposes.

Abstract: A broadcast system is disclosed that allows a broadcaster to provide multiple levels of subscription services. Subscribers have the option of listening to fewer (or no) commercials if they pay a higher fee, or listening to more commercials if they pay a lower (or no) fee. Commercials can be demographically targeted, cannot be skipped, and can be audited for billing purposes.

Abstract: The present invention relates to media broadcast in which memory is used to reduce annoying signal dropouts. A receiver records dropout-free program material and, when a subscriber requests a particular program channel, the radio uses recorded dropout-free program material from the requested channel, only switching to the real-time broadcast, which is subject to dropouts, if the recorded dropout-free program material for the requested channel is exhausted.

Abstract: A broadcast system is disclosed that allows a broadcaster to provide multiple levels of subscription services. Subscribers have the option of listening to fewer (or no) commercials if they pay a higher fee, or listening to more commercials if they pay a lower (or no) fee. Commercials can be demographically targeted, cannot be skipped, and can be audited for billing purposes.

Abstract: A method is disclosed for authenticating one or both of two parties, for example, a user and a host computer. The first party and second party each know the same password. The first party sends a challenge to the second party. The second party generates and sends to the first party a response based on a first function of the password, the first party's challenge, and an extra value unknown to the first party. The first party, which knows only the length of the extra value, then attempts to match the response by using the same function, password, and challenge by cycling through the possible values for the extra value of known format. A method of bi-directional authentication may be achieved by having the first party return to the second party a response using a different function of the password, a preferably different challenge, and the extra value. The second party already knows the input values, including the extra value, and therefore, does not incur the costs associated with learning the extra value.

Abstract: Software (programs, videogames, music, movies, etc.) can be authorized for use a given number of times by a base unit after which the base unit (computer, videogame base unit, record player, videorecorder or videodisk player) cannot use that software until the manufacturer sends an authorization for additional uses to the user's base unit. Authorizations may be sent via telephone line, mail, or whatever form of communication is most suited to the application. Authorizations cannot be reused, for example by recording the telephone authorization signal and replaying it to the base unit. Similarly, authorizations can be made base unit specific, so that an authorization for one base unit cannot be transferred to another base unit. This invention also solves the "software piracy problem" and allows telephone sales of software as additional benefits.

Abstract: In an encryption scheme based on the use of a public key having secret factors p and q, additional requirements on p and q are invoked in order to ensure a high level of security. In particular, it is additionally required that a value p+1 have a large prime factor r and that the value r-1 also have a large prime factor r'.

Abstract: A cryptographic system transmits a computationally secure cryptogram that is generated from a secret transformation of the message sent by the authorized transmitter; the cryptogram is again transformed by the authorized receiver using a secret reciprocal transformation to reproduce the message sent. The secret transformations use secret cipher keys that are known only by the authorized transmitter and receiver. The transformations are performed with nonsecret operations, exponentiation, that are easily performed but extremely difficult to invert. It is computationally infeasible for an eavesdropper either to solve known plaintext-ciphertext pairs for the secret cipher keys, or to invert the nonsecret operations that are used to generate the cryptogram.

Abstract: A cryptographic system transmits a computationally secure cryptogram that is generated from a publicly known transformation of the message sent by the transmitter; the cryptogram is again transformed by the authorized receiver using a secret reciprocal transformation to reproduce the message sent. The authorized receiver's transformation is known only by the authorized receiver and is used to generate the transmitter's transformation that is made publicly known. The publicly known transformation uses operations that are easily performed but extremely difficult to invert. It is infeasible for an unauthorized receiver to invert the publicly known transformation or duplicate the authorized receiver's secret transformation to obtain the message sent.

Abstract: A cryptographic system transmits a computationally secure cryptogram over an insecure communication channel without prearrangement of a cipher key. A secure cipher key is generated by the conversers from transformations of exchanged transformed signals. The conversers each possess a secret signal and exchange an initial transformation of the secret signal with the other converser. The received transformation of the other converser's secret signal is again transformed with the receiving converser's secret signal to generate a secure cipher key. The transformations use non-secret operations that are easily performed but extremely difficult to invert. It is infeasible for an eavesdropper to invert the initial transformation to obtain either conversers' secret signal, or duplicate the latter transformation to obtain the secure cipher key.