Add MFKey to firmware

applications/system/mfkey/crypto1.c

@@ -0,0 +1,22 @@
+#pragma GCC optimize("O3")
+#pragma GCC optimize("-funroll-all-loops")
+
+#include <inttypes.h>
+#include "crypto1.h"
+#include "mfkey.h"
+
+#define BIT(x, n) ((x) >> (n) & 1)
+
+void crypto1_get_lfsr(struct Crypto1State* state, MfClassicKey* lfsr) {
+    int i;
+    uint64_t lfsr_value = 0;
+    for(i = 23; i >= 0; --i) {
+        lfsr_value = lfsr_value << 1 | BIT(state->odd, i ^ 3);
+        lfsr_value = lfsr_value << 1 | BIT(state->even, i ^ 3);
+    }
+
+    // Assign the key value to the MfClassicKey struct
+    for(i = 0; i < 6; ++i) {
+        lfsr->data[i] = (lfsr_value >> ((5 - i) * 8)) & 0xFF;
+    }
+}