Examples of Compiler-Based Information Flow Enforcement Mechanisms

Here are some examples.

copy2 

procedure copy2(x: integer class {x};
  var y: integer class {x});
      "copy x to y"
  var z: integer class {x});
  begin
    z := 1;
    y := -1;
    while z = 1 do
    begin
      y := y + 1;
      if y = 0
      then z := x
      else z := 0
    end
  end
end copy2.

 
 
 
 
 
Low < z
Low < y
z < y CIRCLEPLUS z
 
y < y
y < z
x < z
Low < z
 
 
 
copy2 with goto 
procedure copy2(x: integer class {x};
    var y: integer class {x});
        "copy x to y"
    var z: integer class {x};
    begin
1:  z := 1;
    y := -1;
2:  if z <> 1 then goto 6;
3:  y := y + 1;
    if y <> 0 then goto 5;
4:  z := x;
    goto 2;
5:  z := 0;
    goto 2;
6:  end
end copy2.

 
 
 
 
 
b1
 
b2
b3
 
b4
 
b5
 
 
 

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Department of Computer Science
University of California at Davis
Davis, CA 95616-8562


Page last modified on 3/19/99