From d7f80c6f45563ff390bafad2ef5d34346449f70f Mon Sep 17 00:00:00 2001
From: pthomalla <pawel.thomalla@imapp.pl>
Date: Sun, 25 Nov 2018 15:44:58 +0100
Subject: [PATCH 1/2] fix modulo

---
 lib/math/math.ex | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/lib/math/math.ex b/lib/math/math.ex
index c04dc67..6add982 100644
--- a/lib/math/math.ex
+++ b/lib/math/math.ex
@@ -19,10 +19,17 @@ defmodule ExthCrypto.Math do
 
       iex> ExthCrypto.Math.mod(0, 1337)
       0
+
+      iex> ExthCrypto.Math.mod(-75, 32)
+      21
   """
-  def mod(x, n) when x > 0, do: rem x, n
-  def mod(x, n) when x < 0, do: rem n + x, n
-  def mod(0, _n), do: 0
+  def mod(x, n) do
+    remainder = rem(x, n)
+
+    if remainder < 0,
+      do: n + remainder,
+      else: remainder
+  end
 
   @doc """
   Simple wrapper function to convert a hex string to a binary.
@@ -108,4 +115,4 @@ defmodule ExthCrypto.Math do
     :crypto.exor(a, b)
   end
 
-end
\ No newline at end of file
+end

From e47c4e2652d192ead4bea7a18e8085113d730e90 Mon Sep 17 00:00:00 2001
From: pthomalla <pawel.thomalla@imapp.pl>
Date: Wed, 28 Nov 2018 10:05:12 +0100
Subject: [PATCH 2/2] divisor can be negative

---
 lib/math/math.ex | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/lib/math/math.ex b/lib/math/math.ex
index 6add982..7f5b879 100644
--- a/lib/math/math.ex
+++ b/lib/math/math.ex
@@ -22,11 +22,17 @@ defmodule ExthCrypto.Math do
 
       iex> ExthCrypto.Math.mod(-75, 32)
       21
+
+      iex> ExthCrypto.Math.mod(75, -32)
+      -21
+
+      iex> ExthCrypto.Math.mod(-10,-3)
+      -1
   """
   def mod(x, n) do
     remainder = rem(x, n)
 
-    if remainder < 0,
+    if (remainder < 0 and n > 0) or (remainder > 0 and n < 0),
       do: n + remainder,
       else: remainder
   end