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Bitcoin needs to be so secure you can use it at an internet cafe.
The current reference Bitcoin client
running on GNU/Linux meets this requirement.
It's secure if you use 4g, I highly doubt big communications providers will be stealing your bitcoin
It's not about doubt, it's about being 100% sure you are the only one in control of your coins. The only way to do that is to have a open source dedicated device for cold storage and offline signing (trezor/rPi)