 For "a" and "b" elements of formula_65, we say that the prover proves knowledge of formula_66 and formula_67 such that formula_68 and formula_69.Equality corresponds to the special case where "a" = 1 and "b" = 0.As formula_67 can be trivially computed from formula_66 this is equivalent to proving knowledge of an "x" such that formula_72.