From c4446c32a0fd6e829959ca2bf84bbad211554a87 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Andreas=20M=C3=BCller?= <andreas.mueller@othello.ch>
Date: Tue, 6 Apr 2021 16:40:17 +0200
Subject: add new stuff

---
 buch/chapters/90-crypto/images/sbox.m | 52 +++++++++++++++++++++++++++++++++++
 1 file changed, 52 insertions(+)
 create mode 100644 buch/chapters/90-crypto/images/sbox.m

(limited to 'buch/chapters/90-crypto/images/sbox.m')

diff --git a/buch/chapters/90-crypto/images/sbox.m b/buch/chapters/90-crypto/images/sbox.m
new file mode 100644
index 0000000..973ffc9
--- /dev/null
+++ b/buch/chapters/90-crypto/images/sbox.m
@@ -0,0 +1,52 @@
+#
+# sbox.m
+#
+# (c) 2021 Prof Dr Andreas Müller, OST Ostschweizer Fachhochschule
+#
+A=[
+1,0,0,0,1,1,1,1;
+1,1,0,0,0,1,1,1;
+1,1,1,0,0,0,1,1;
+1,1,1,1,0,0,0,1;
+1,1,1,1,1,0,0,0;
+0,1,1,1,1,1,0,0;
+0,0,1,1,1,1,1,0;
+0,0,0,1,1,1,1,1;
+]
+
+R = zeros(8,16);
+R(:,1:8) = A;
+R(:,9:16) = eye(8);
+
+for k = (1:5)
+	for i=(k+1:8)
+		pivot = R(i,k);
+		R(i,:) = R(i,:) + pivot * R(k,:);
+	end
+	R = mod(R, 2)
+end
+
+P = [
+1,0,0,0,0,0,0,0;
+0,1,0,0,0,0,0,0;
+0,0,1,0,0,0,0,0;
+0,0,0,1,0,0,0,0;
+0,0,0,0,1,0,0,0;
+0,0,0,0,0,0,0,1;
+0,0,0,0,0,1,0,0;
+0,0,0,0,0,0,1,0;
+]
+
+R = P * R
+
+for k = (8:-1:2)
+	for i = (1:k-1)
+		pivot = R(i,k);
+		R(i,:) = R(i,:) + pivot * R(k,:);
+	end
+	R = mod(R, 2)
+end
+
+B = R(:,9:16)
+
+A * B
-- 
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