Matthew J Ghio wrote:
1 1 2 1 2 1 1 2 1 y = - ( - x + - x + C ) + - ( - x + - x + C ) + D 2 2 2 2 2 2
4 3 2 y = .125x + .25x + 63.875x + 63.75x + 8159
By expanding the equation above (the top one), I got this: y = 1/8*x^4 + 1/4*x^3 + (3/8 + c/2)*x^2 + (1/4 + c/2)*x + (1/2*c + 1/2*c^2 + d) and by matching powers, got the following equations: c/2 + 3/8 = 63.875 1/2*c^2 + 1/2*c + d = 8159 These equations are easily solved for c = 127, d = 31. From there, I can compute the required inverse equations, and so on. I'm not too sure about the security of this method; it seems it boils down to solving simultaneous equations, which yield the constant terms. And you even know how many nested equations there are from the power of the leading term. But, as a test, post a harder one (maybe four or more nestings) and see if I can get it! -- Karl L. Barrus: klbarrus@owlnet.rice.edu keyID: 5AD633 hash: D1 59 9D 48 72 E9 19 D5 3D F3 93 7E 81 B5 CC 32 "One man's mnemonic is another man's cryptography" - my compilers prof discussing file naming in public directories