Securing a cryptographic device

A system for secure communication of data, said system comprising:

• a host device with a host microprocessor and host memory, wherein the host device comprises a master key stored within the host memory and a pseudorandom generator;
• a client device with a client microprocessor and client memory, wherein the client device comprises an encryption module;
• a secure connection between the host device and the client device;
• and is configured to derive a pseudorandom function family from pseudorandom outputs in the encryption module with the master key and chunk-wise processing of an initialization vector and a plurality of secret values generated by the pseudorandom generator, wherein each chunk of a plurality of chunks in the initialization vector is used to select a respective secret value as an input to the encryption module, and use said pseudorandom function family for encrypting communication between the client device and the host device.

A system for providing authenticated communication of data, said system comprising:

• a host device with a host microprocessor and host memory wherein the host device comprises a master key stored within the host memory and a pseudorandom generator;
• a client device with a client microprocessor and client memory wherein the client device comprises an encryption module;
• an authenticated connection between the host device and the client device;
• wherein the client device is configured to derive a pseudorandom function family from pseudorandom outputs in the encryption module with the master key and chunk-wise processing of an initialization vector and a plurality of secret values generated by the pseudorandom generator, wherein each chunk of a plurality of chunks in the initialization vector is used to select a respective secret value as an input to the encryption module, and use said pseudorandom function family for authenticating communication between the client device and the host device by using the pseudorandom outputs as a message authentication code.