Computers on the 27th century are very small and very powerful. The most common human-computer interface is a WNT (Wearable Network Terminal), a wearable configuration that acts as an arm sleeve or an entire shirt. These devices have minimal storage capabilities, modest processing power, a simple display for output and a microphone for voice commands input. Extensions are available that provide additional capabilities, ranging from inexpensive speakers to expensive miniature holographic projectors.
All larger computers are part of the Earthnet, a large distributed computing and storage network that everyone gets basic access to for free.
Quantum cryptography makes secure communications really secure against eavesdropping. However, due to the costs of establishing quantum channels between distant endpoints its use is restricted to the transmission of OTP keys.