Method and system for securing communication between a host computer and a secure portable device

A secure portable electronic device for providing secure services when used in conjunction with a host computer having a central processing unit of a first type, the secure portable electronic device having a central processing unit of a second type, wherein a secure service is provided by executing an application in a flexible distributed fashion among the host computer and the secure portable electronic device, comprising:

• a read-only memory partition, a read/write memory partition, and a secure memory partition;
• a communications interface for securely transmitting and receiving data between the host computer and the secure portable electronic device using a communications protocol over the communications interface, wherein communications between secure portable device and the host computer are secured by encryption using a symmetric key;
• instructions stored in the read-only partition, wherein the instructions comprise:
• a host agent containing instructions executable by a central processing unit of the first type;
• private information stored in the secure memory partition;
• and
• instructions stored in the secure memory partition, comprising:
• a card agent containing instructions executable by central processing units of the second type, the instructions including instructions to cause the secure device to:
• receive a message from a host agent executing on the host computer requesting to diversify the symmetric key established to secure communication between the host agent executing on the host computer and the card agent executing on the secure device to establish a replacement value for the symmetric key;
• in response to receiving a key diversification request, transmit a message to request a thumbprint of the host agent instructions executing on the host computer;
• receive a message containing a thumbprint from the host computer;
• compare the received thumbprint against a known-to-be-correct thumbprint;
• prevent further access to secure data stored on the secure device by the host computer if the received thumbprint does not match the known-to-be-correct thumbprint;
• and
• continue key diversification operations if the received thumbprint matches the known-to-be-correct thumprint;
• the host agent comprising instructions including instructions to:
• compute a thumbprint;
• and
• transmit the computed thumbprint to the secure device.