Add image shift example program

CameronLonsdale · Jun 5, 2019 · a8d1eb8 · a8d1eb8
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diff --git a/examples/shift/example.png b/examples/shift/example.png
diff --git a/examples/shift/image_shift.py b/examples/shift/image_shift.py
@@ -0,0 +1,23 @@
+#!/usr/bin/env python3
+
+from lantern.modules import shift
+
+
+shift_encrypt = lambda key, byte: (byte + key) % 255
+shift_decrypt = lambda key, byte: (byte - key) % 255
+
+
+with open("example.png", "rb") as image:
+    image_bytes = bytearray(image.read())
+
+KEY = 144
+encrypted_bytes = shift.encrypt(KEY, image_bytes, shift_encrypt)
+
+print(f"Encrypted header: {encrypted_bytes[:8]}")
+
+header_matcher = lambda value: 0 if value[:8] == [137, 80, 78, 71, 13, 10, 26, 10] else -1
+
+# Decrypt the image by finding a matching PNG header
+decryptions = shift.crack(encrypted_bytes, header_matcher, min_key=0, max_key=255, shift_function=shift_decrypt)
+
+print(f"Decrypted Header: {decryptions[0].plaintext[:8]}")