diff --git a/Source/scalable/scalable_power.ml b/Source/scalable/scalable_power.ml
index 5fed77a..6580bc9 100644
--- a/Source/scalable/scalable_power.ml
+++ b/Source/scalable/scalable_power.ml
@@ -11,13 +11,25 @@ open Scalable_basic_arithmetics
     @param x base, a bitarray
     @param n exponent, a non-negative bitarray
  *)
-let pow x n = []
+let pow x n =
+  let rec pow_rec x1 n =
+    match n with
+        [] -> x1
+      | n -> pow_rec (mult_b x1 x) (diff_b n [0;1])
+  in pow_rec [0;1] n;;
 
 (** Fast bitarray exponentiation function. Logarithmic complexity.
     @param x base, a bitarray
     @param n exponent, a non-negative bitarray
  *)
-let power x n = []
+let power x n =
+  if n = [] then [0;1] else
+  let rec power_rec x1 n =
+    match n with
+        [0;1] -> x1
+      | n when mod_b n [0;0;1] = [] -> power_rec (mult_b x1 x1) (quot_b n [0;0;1])
+      | n -> mult_b x1 (power_rec (mult_b x1 x1) (quot_b (diff_b n [0;1]) [0;0;1]))
+  in power_rec x n;;
 
 (* Modular expnonentiation ; modulo a given natural (bitarray without
    sign bits).
@@ -28,7 +40,17 @@ let power x n = []
     @param n exponent, a non-negative bitarray
     @param m modular base, a positive bitarray
  *)
-let mod_power x n m = []
+let mod_power x n m =
+  if n = [] then
+    [0;1]
+  else
+    let rec mod_power_rec c e =
+      let c = mod_b (mult_b x c) m
+      in if (<<) e n then
+          mod_power_rec c (add_b e [0;1])
+        else
+          c
+    in mod_power_rec [0;1] [0;1];;
 
 (* Making use of Fermat Little Theorem for very quick exponentation
    modulo prime number.
@@ -40,4 +62,8 @@ let mod_power x n m = []
     @param n exponent, a non-negative bitarray
     @param p prime modular base, a positive bitarray
  *)
-let prime_mod_power x n p = []
+let prime_mod_power x n p =
+  if x = [] then
+    []
+  else
+    mod_power x (mod_b n (diff_b p [0;1])) p;;