Substituiton

This commit is contained in:
Simon Freiermuth 2022-03-17 14:40:35 +01:00
parent 682cd6f814
commit 0851f73c88
4 changed files with 70 additions and 0 deletions

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@ -1,7 +1,40 @@
package ch.fhnw.kry;
import java.util.Map;
import java.util.HashMap;
import static java.util.Map.entry;
public class SPN {
private final static int ROUND_KEY_LENGTH = 16;
private final Map<Integer, Integer> SBOX = Map.ofEntries(
entry(0xE, 0),
entry(4, 1),
entry(0xD, 2),
entry(1, 3),
entry(2, 4),
entry(0xF, 5),
entry(0xB, 6),
entry(8, 7),
entry(3, 8),
entry(0xA, 9),
entry(6, 0xA),
entry(0xC, 0xB),
entry(5, 0xC),
entry(9, 0xD),
entry(0, 0xE),
entry(7, 0xF)
);
public String decrypt(int key, String chiffre) {
return null;
}
public int sp (int key, int x) {
x = init(key, x);
return x;
}
public int k(int key, int i) {
i *= 4;
@ -9,4 +42,23 @@ public class SPN {
return key & mask >>> ROUND_KEY_LENGTH - i;
}
public int init(int key, int x) {
return x ^ k(key, 4);
}
public int substitution(int x) {
int mask = 0xF000;
for (int i = 0; i < 4; i++) {
int j = 4 * i;
int key = (x & mask) >>> 12 - j;
int val = SBOX.get(key);
int replMask = ~(0xf << 12 - j); // Maske mit 4 0-Bits vorbereiten zur Vorbereitung vom Einfügen
x = x & replMask | (val << 12 - j); // x an der Stelle der 4 0-Bits mit val überschreiben
mask = mask >>> 4; // maske um 4 Bit für nächste Iteration verschieben
}
return x;
}
}

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@ -15,4 +15,22 @@ class SPNTest {
assertEquals(0xFFFF, spn.k(key, 1));
assertEquals(0xFFFF, spn.k(key, 2));
}
@Test
void substitution() {
var spn = new SPN();
//given
int x = 0xEF45;
int r = 0x051C;
System.out.print(Integer.toHexString(x));
//when
int y = spn.substitution(x);
// then
assertEquals(r, y);
// System.out.print(Integer.toHexString(spn.substitution(x)));
}
}