groups (such as hotels, cable companies, or paid subscribers) or to specific political regions. Early encryption attempts such as Videocipher II were common targets for pirate decryption as dismayed viewers saw large amounts of formerly-unencrypted programming vanishing. Nowadays some free-to-air satellite content in the USA still remains, but many of the channels still in the clear are ethnic channels, local over-the-air TV stations, international broadcasters, religious programming, backfeeds of network programming destined to local TV stations or signals uplinked from mobile satellite trucks to provide live news and sports coverage. Specialty channels and premium movie channels are most often encrypted; in most countries, broadcasts containing explicit pornography must always be encrypted to prevent reception by those who wish children not to be exposed to this sort of content. Technical issues Initial attempts to encrypt broadcast signals were based on analogue techniques of questionable security, the most common being one or a combination of techniques such as: Weakening or attenuating specific portions of the video signal, typically those required to maintain synchronization. Inverting video signals so that white becomes black (and vice versa). Adding an interfering signal at one specific frequency which could be simply filtered out at a suitably equipped receiver. Moving the audio portion of the signal to some other frequency or sending it in a non-standard format. These systems were designed to provide decoders to cable operators at low cost; a serious tradeoff was made in security. Some analogue decoders were addressable so that cable companies could turn channels on or off remotely, but this only gave the cable companies control of their own descramblers — valuable if needed to deactivate a stolen cable company decoder but useless against hardware designed by signal pirates. The first encryption methods used for big-dish satellite systems used a hybrid approach; analogue video and digital encrypted audio. This approach was somewhat more secure, but not completely free of problems due to piracy of video signals. Direct broadcast satellites and digital cable services, because of their digital format, are free to use more robust security measures such as the Data Encryption Standard (DES) or the RSA and IDEA digital encryption standards. When first introduced, digital DBS broadcasts were touted as being secure enough to put an end to piracy once and for all. Often these claims would be made in press releases. The enthusiasm was short-lived. In theory the system was an ideal