diff --git a/Source/scalable/scalable_basic_arithmetics.ml b/Source/scalable/scalable_basic_arithmetics.ml
index 83e1223..2310aae 100644
--- a/Source/scalable/scalable_basic_arithmetics.ml
+++ b/Source/scalable/scalable_basic_arithmetics.ml
@@ -2,11 +2,20 @@
 
 open Scalable
 
+let sign l =
+    match sign_b l with
+        1 -> [0;1]
+      | _ -> [1;1]
+
 (** Greater common (positive) divisor of two non-zero integers.
     @param bA non-zero bitarray.
     @param bB non-zero bitarray.
 *)
-let gcd_b bA bB = []
+let rec gcd_b bA bB =
+  let r = mod_b (mult_b (sign bA) bA) (mult_b (sign bB) bB)
+  in if (>>!) r [] then
+      gcd_b (mult_b (sign bB) bB) r
+    else bB;;
 
 (** Extended euclidean division of two integers NOT OCAML DEFAULT.
     Given non-zero entries a b computes triple (u, v, d) such that
@@ -14,4 +23,11 @@ let gcd_b bA bB = []
     @param bA non-zero bitarray.
     @param bB non-zero bitarray.
 *)
-let bezout_b bA bB = ([], [], [])
+let bezout_b bA bB =
+  let rec bezout_b_rec u v r u1 v1 r1=
+    if r1 = [] then
+      (u, v, add_b (mult_b bA u) (mult_b bB v))
+    else
+      let q = quot_b r r1 in
+      bezout_b_rec u1 v1 r1 (diff_b u (mult_b q u1)) (diff_b v (mult_b q v1)) (diff_b r (mult_b q r1))
+  in bezout_b_rec [0;1] [] bA [] [0;1] bB;;