An encryption circuit for simultaneously processing various encryption algorithms, the circuit being capable of being coupled with a host system hosted by a computing machine. The circuit comprises an input/output module responsible for the data exchanges between the host system and the circuit via a dedicated bus. An encryption module coupled with the input/output module is in charge of the encryption and decryption operations. Isolation means between the input/output module and the encryption module makes the sensitive information stored in the encryption module inaccessible to the host system and ensures the parallelism of the operations performed by the input/output module and the encryption module. The circuit is supported on a peripheral component interconnect card. The circuit is specifically adapted to provide "hardware" protection of computer servers or stations.