Obfuscation of Abstract Data-Types - Rowan

More documents

Recommendations

Info

CHAPTER 2. OBFUSCATIONS FOR INTERMEDIATE LANGUAGE 41 be useful to have loops in our language and so we need to recover loops as well as expressions from IL. Baker [5] gives an algorithm for transforming a flow graph into a program which contains constructs such as if/then/else and repeat and Ramshaw [44] shows how many goto statements can be eliminated. An algorithm is given in [24] which eliminates goto statements by applying a sequence of transformations to move a goto. This is followed by a gotoeliminating transformation which introduces extra variables and predicates. Extensions of EIL and PLP are discussed in [47] in which the specification language has a new primitive: paths(B,P) which states that all paths through B satisfy the pattern P and the language can match expressions of the form: while(Cond,Body) These extensions should allow the specification in Section 2.3.8 to be written more succinctly. 2.4.2 Transformation Systems PLP uses the idea of Universal Regular Path Queries [14] in which transformations are expressed as logic predicates using regular expressions. The APTS system of Paige [41] was also a major source of inspiration. In APTS, program transformations are expressed as rewrite rules, with side conditions expressed as Boolean functions on the abstract syntax tree, and data obtained by program analyses. As mentioned in Section 2.3.5, the strategy language used in the toolkit was based on Stratego [55]. Some other transformation systems that provided inspiration for PLP are briefly described below. • TyRuBa [17] is based on representing programs as logic propositions. The system is not really used for program transformations; instead it is used for the implementation of classes and interfaces. • Gospel [56] is a specification language to express program-improving transformations. This needs a declaration of variables (which might be statements), a precondition consisting of a code pattern and dependencies and an action. • TRANS [31] is a language in which temporal logic is used to specify transformations with rewrite rules. The specification language has constructors such as E (there exist a path) and A (for all paths) for expressing paths in a control flow graph. 2.4.3 Correctness Throughout this chapter we have not been concerned with the correctness of the transformations, i.e. whether a transformation is behaviour-preserving. Proving the correctness of a transformation is a challenging task. In [33] a framework is provided for proving the correctness of compiler optimisations that are expressed
CHAPTER 2. OBFUSCATIONS FOR INTERMEDIATE LANGUAGE 42 in temporal logic. A simple language consisting of read, write, assignments, conditionals and jumps (but not procedures or exceptions) is considered and a semantics for this language is given. A method for showing semantic equivalence is stated and used to prove the correctness of some optimisations. This method is quite complicated but seems suited to automation — a technique for automatically proving the soundness of optimisations is given in [34]. The proofs given in [33] are difficult since they require setting up complicated semantics and a proof is too detailed to be stated here. For instance, the proof of a code motion transformation takes one whole double column page. This method could be adapted for our obfuscations but would be a very demanding task. 2.5 Conclusions We have seen that there is a need for obfuscating the .NET Intermediate Language and we have given a way of specifying obfuscations for IL. We have seen that by changing certain predicates in the specification we can specify more general obfuscations. Proving the correctness of transformations requires considerable effort and theoretical techniques (such as developing semantics) which are detailed and complicated. The proofs also require simplifying the source language. Thus proving the correctness of our obfuscations will be a challenging task. Using IL also makes proofs difficult as it is a low-level language. In the rest of the thesis, we will consider obfuscating abstract data-types. We will model operations as functional programs and we consider obfuscation as data refinement. We will find that using abstract data-types makes proving correctness easier and in some cases we will be able to derive obfuscated operations.
Page 1 and 2: Obfuscation of Abstract Data-Types
Page 3 and 4: Contents I The Current View of Obfu
Page 5 and 6: 5.4.3 Third Definition . . . . . .
Page 7 and 8: List of Figures 1 An example of obf
Page 9 and 10: 8 public class c { d t1 = new d();
Page 11 and 12: 10 • Obfuscations can be proved c
Page 13 and 14: Chapter 1 Obfuscation Scully: “No
Page 15 and 16: CHAPTER 1. OBFUSCATION 14 These thr
Page 17 and 18: CHAPTER 1. OBFUSCATION 16 by changi
Page 19 and 20: CHAPTER 1. OBFUSCATION 18 We could
Page 21 and 22: CHAPTER 1. OBFUSCATION 20 B 1 [0] =
Page 23 and 24: Chapter 2 Obfuscations for Intermed
Page 25 and 26: CHAPTER 2. OBFUSCATIONS FOR INTERME
Page 41: CHAPTER 2. OBFUSCATIONS FOR INTERME
Page 45 and 46: Chapter 3 Techniques for Obfuscatio
Page 47 and 48: CHAPTER 3. TECHNIQUES FOR OBFUSCATI
Page 63 and 64: Part III Data-Type Case Studies 62
Page 65 and 66: CHAPTER 4. SPLITTING HEADACHES 64 (
Page 67 and 68: CHAPTER 4. SPLITTING HEADACHES 66 a
Page 69 and 70: CHAPTER 4. SPLITTING HEADACHES 68 T
Page 71 and 72: CHAPTER 4. SPLITTING HEADACHES 70 L
Page 73 and 74: CHAPTER 4. SPLITTING HEADACHES 72 S
Page 75 and 76: CHAPTER 4. SPLITTING HEADACHES 74 C
Page 77 and 78: CHAPTER 4. SPLITTING HEADACHES 76 L
Page 79 and 80: CHAPTER 4. SPLITTING HEADACHES 78 t
Page 81 and 82: CHAPTER 4. SPLITTING HEADACHES 80 C
Page 83 and 84: CHAPTER 4. SPLITTING HEADACHES 82 4
Page 85 and 86: CHAPTER 4. SPLITTING HEADACHES 84 E
Page 87 and 88: CHAPTER 4. SPLITTING HEADACHES 86 b
Page 89 and 90: CHAPTER 4. SPLITTING HEADACHES 88 W
Page 91 and 92: CHAPTER 4. SPLITTING HEADACHES 90 T
Page 93 and 94:
Chapter 5 Sets and the Splitting Bu
Page 95 and 96:
CHAPTER 5. SETS AND THE SPLITTING 9
Page 97 and 98:
Page 99 and 100:
Page 101 and 102:
Page 103 and 104:
Page 105 and 106:
Page 107 and 108:
Page 109 and 110:
CHAPTER 6. THE MATRIX OBFUSCATED 10
Page 111 and 112:
Page 113 and 114:
Page 115 and 116:
Page 117 and 118:
Page 119 and 120:
Page 121 and 122:
CHAPTER 7. CULTIVATING TREE OBFUSCA
Page 123 and 124:
Page 125 and 126:
Page 127 and 128:
Page 129 and 130:
Page 131 and 132:
Page 133 and 134:
Page 135 and 136:
Chapter 8 Conclusions and Further W
Page 137 and 138:
CHAPTER 8. CONCLUSIONS AND FURTHER
Page 139 and 140:
CHAPTER 8. CONCLUSIONS AND FURTHER
Page 141 and 142:
BIBLIOGRAPHY 140 [13] Thomas H. Cor
Page 143 and 144:
BIBLIOGRAPHY 142 [43] Simon Peyton
Page 145 and 146:
Appendix A List assertion We want t
Page 147 and 148:
APPENDIX A. LIST ASSERTION 146 Case
Page 149 and 150:
APPENDIX A. LIST ASSERTION 148 For
Page 151 and 152:
APPENDIX A. LIST ASSERTION 150 Case
Page 153 and 154:
APPENDIX A. LIST ASSERTION 152 1 +
Page 155 and 156:
APPENDIX A. LIST ASSERTION 154 0 +
Page 157 and 158:
APPENDIX A. LIST ASSERTION 156 The
Page 159 and 160:
APPENDIX A. LIST ASSERTION 158 The
Page 161 and 162:
APPENDIX B. SET OPERATIONS 160 Now
Page 163 and 164:
APPENDIX B. SET OPERATIONS 162 Proo
Page 165 and 166:
APPENDIX B. SET OPERATIONS 164 B.2
Page 167 and 168:
Appendix C Matrices We prove the as
Page 169 and 170:
APPENDIX C. MATRICES 168 Base Case
Page 171 and 172:
APPENDIX D. PROVING A TREE ASSERTIO
Page 173 and 174:
Page 175 and 176:
Page 177 and 178:
Page 179 and 180:
Page 181 and 182:
Page 183 and 184:
Page 185 and 186:
Page 187:
APPENDIX E. OBFUSCATION EXAMPLE 186
show all

Obfuscation of Abstract Data-Types - Rowan

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?