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Nicholas Moore Bianca Curutan Pooya Samizadeh McMaster University March 30, 2012.

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Presentation on theme: "Nicholas Moore Bianca Curutan Pooya Samizadeh McMaster University March 30, 2012."— Presentation transcript:

1 Nicholas Moore Bianca Curutan Pooya Samizadeh McMaster University March 30, 2012

2 Introduction TAL and PCC TAL-0 TAL-1 Real World Application

3  Typed Assembly Language (TAL) extends traditional untyped assembly languages with typing annotations, memory management primitives, and a sound set of typing rules  These typing rules guarantee the memory safety, control flow safety, and type safety of TAL programs

4  Principle of Proof-Carrying Code (PCC): Eliminate the need to trust code by requiring a formal, machine-checkable proof that the code has some desired properties 1. What properties should we require of the code? 2. How do code producers construct a formal proof that their code has the desired properties?

5  Control-flow Safety: Ensure that a program jumps only to a well-defined subset of possible entry points  A focus on control-flow safety allows us to develop a simple abstract machine and demonstrate the key ideas of adapting a type system to machine code

6  Instructions and Operands

7  Abstract Machine Syntax

8  Syntax additions

9  Limitations: ◦ Only supports simple tuple or record-like data structures ◦ Insufficient for compiling real-world high-level languages which provide data abstraction mechanisms ◦ Can only allocate objects whose size is known at compile time

10  Examples to make type system more useful: ◦ Annotate primitive memory type components with flags to control whether that component supports read-only, write-only, or read-write access ◦ Add support for subtyping ◦ Consider a read-write component to be a subtype of a read-only or a write-only component

11 Introduction Touchstone PCC Architecture Advantages Over Related Techniques Technical Difficulties to Overcome

12  Proof-Carrying Code (PCC): General framework that allows the host to verify properties about an agent via a formal proof that accompanies the executable code  The host system can quickly verify the validity of the proof and compare the conclusions to its own security policy to determine if the agent has certain safety properties

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14 1. Operates at load time before the agent code is installed in the host system 2. Trusted computing base is small 3. Can operate even on agents expressed in native-code form 4. General – all PCC has to do is verify safety explanations and match them with the code and safety policy

15  How to encode the formal proof?  How to check the proof?  How to relate the proof with the program?

16 Introduction Recall TAL-0 Example (Quotient) Description and Demo

17  Task ◦ Build an interpreter for the TAL-0 abstract machine in Haskell (i.e., functional programming language).  Extra ◦ Literate programming using LaTeX

18  Instructions and Operands  Abstract Machine Syntax

19 # reduce register r1 to 0 init|r1 := 10; r2:=11; => loop; loop|? r1 => done; r1 := r1 + -1; r1:=8; => loop; done|

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21  Jones, Mark. Functional Programming with Overloading and Higher-Order Polymorphism. Diss. University of Nottingham. Nottingham. Print.  Liang, Sheng, Paul Hudak, and Mark Jones. Monad Transformers and Modular Interpreters. Diss. Yale University. New Haven. Print.  Necula, George. "Proof-Carrying Code." Computer Science Division, EECS at UC Berkeley. 22 July Web. 21 Mar  Pierce, Benjamin C. Advanced Topics in Types and Programming Languages. Cambridge, MA: MIT, Print.  "Typed Assembly Language Compiler." Cornell University Department of Computer Science. Web. 21 Mar


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