Z:gnu-www-ja-software-patents--d9ba39-Sometimes the idea that's pate/en

Sometimes the idea that's patented will be so broad and basic that it basically rules out an entire field. For instance, the idea of Public Key Encryption which was patented in the US. The patent expired in 1997. Until then, it largely blocked the use of Public Key Encryption in the US. A number of programs that people started to develop got crushed. They were never really available because the patent holders threatened them.