Are there any countries where it is illegal to use Silent Phone?

There are some countries where the sale and use of encryption software is prohibited, such as China, North Korea, and a handful of others, usually due to lawful intercept regulations. However, the rules prohibiting the use of encryption typically only apply to the purchase of such products within the country or the use of such products by citizens or residents of the country, but not to non-residents who lawfully purchase products or services abroad. We are not aware of any regulations prohibiting visitors from carrying encryption software into countries where travel is permitted, and many devices and software products such as iphone, internet browsers, etc. contain some level of encryption software.