Abstract: One embodiment includes hardware-based cybersecurity devices that create a physical barrier (“hardware security barrier”) between a computer's (or other device's) processor and a public or private network. Hardware security barriers typically use immutable hardware in accomplishing cybersecurity activities including generating and distributing cryptographically secure numbers, encryption, decryption, source authentication, and packet integrity verification. This hardware security barrier protects against remote threats and guarantees that all exported and received data are strongly encrypted. A hardware security barrier can be included in any computing or networking device that contains a network interface. One embodiment of a hardware security barrier is implemented as part of a network interface, such as, but not limited to being part of a network interface controller, or as a standalone unit between a communications interface of a host system and a connection to a network.