jones_supa writes "The most widely used cellphone encryption cipher A5/1 can be easily defeated by the National Security Agency, an internal document shows. This gives the agency the means to intercept most of the billions of calls and texts that travel over radiowaves every day, even when the agency would not have the encryption key. Encryption experts have long known the cipher to be weak and have urged providers to upgrade to newer systems. Consequently it is also suggested that other nations likely have the same cracking capability through their own intelligence services. The vulnerability outlined in the NSA document concerns encryption developed in the 1980s but still used widely by cellphones that rely on 2G GSM. It is unclear if the agency may also be able to decode newer forms of encryption, such as those covered under CDMA."