This paper introduces the Trusted Execution Module (TEM); a high-level specification for a commodity chip that can execute user-supplied procedures in a trusted environment. The TEM is capable of securely executing partially-encrypted procedures/closures expressing arbitrary computation. These closures can be generated by any (potentially untrusted) party who knows the TEM's public encryption key. Compared to a conventional smartcard, which is typically used by pre-programming a limited set of domain- or application- specific commands onto the smartcard, and compared to the Trusted Platform Module (TPM), which is limited to a fixed set of cryptographic functions that cannot be combined to provide general-purpose trusted computing, the TEM is significantly more flexible. Yet we present a working implementation using existing inexpensive Javacard smartcards that does not require any export-restricted technology. The TEM's design enables a new style of programming, which in turn enables new applications. We show that the TEM's guarantees of secure execution enable exciting applications that include, but are not limited to, mobile agents, peer-to-peer multiplayer online games, and anonymous offline payments.
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