From Architectural Support for Programming Languages and Operating Systems (ASPLOS-IX).
Cambridge, MA.
November, 2000.

Although there have been attempts to develop code transformation that yield tamper-resistant software, no reliable software-only methods are known. This paper studies the hardware implementation of a form of execute-only memory (XOM) that allows instructions stored in memory to be executed but not otherwise manipulated. To support XOM code we use a machine that support internal compartments --- a process in one compartment cannot read data from another compartment. All data that leaves the machine is encrypted, since we a assume external memory is not secure. The design of this machine poses some interesting trade-offs between security, efficiency, and flexibility. We explore some of the potential security issues as one pushes the machine to be come more efficient and flexible. Although security carries a performance penalty, our analysis indicates that it is possible to create a normal multi-tasking machine where nearly all applications can be run in XOM mode. While a virtual XOM machine in possible, the underlying hardware needs to support a unique private key, private memory, and traps on cache misses. For efficient operation, hardware assist to provide fast symmetric ciphers is also required.

@inproceedings{LincolnXOM2000,
    AUTHOR = {{D.} Lie and {C.} Thekkath and {P.} Lincoln and {M.} Mitchell and {D.} Boneh and {J.} Mitchell and {M.} Horowitz},
    TITLE = {Architectural Support for Copy and Tamper Resistant Software},
    BOOKTITLE = {Architectural Support for Programming Languages and Operating Systems (ASPLOS-IX)},
    YEAR = {2000},
    ADDRESS = {Cambridge, {MA}},
    MONTH = {November},
    URL = {http://www.csl.sri.com/papers/lincolnxom2000/}
}

• xom.pdf