Add lab-02-security-as-a-system

lab-02-security-as-a-system/scenario/identity.py

@@ -0,0 +1,42 @@
+#!/usr/bin/env python3
+
+import sys
+
+MODULUS = 1 << 24
+FACTOR = 5
+BIAS = 0x456789
+FACTOR_INVERSE = pow(FACTOR, -1, MODULUS)
+
+
+def pack(value):
+    number = int(value, 16)
+    result = (number * FACTOR + BIAS) % MODULUS
+    return f"{result:06x}"
+
+
+def unpack(value):
+    number = int(value, 16)
+    result = ((number - BIAS) * FACTOR_INVERSE) % MODULUS
+    return f"{result:06x}"
+
+
+def main():
+    if len(sys.argv) != 3:
+        raise SystemExit(2)
+
+    operation = sys.argv[1]
+    value = sys.argv[2].lower()
+
+    if len(value) != 6:
+        raise SystemExit(2)
+
+    if operation == "pack":
+        print(pack(value))
+    elif operation == "unpack":
+        print(unpack(value))
+    else:
+        raise SystemExit(2)
+
+
+if __name__ == "__main__":
+    main()