From ad5cd4c820b094c7cf19b3ab1427f13c98b3af69 Mon Sep 17 00:00:00 2001
From: Elia Marcinkiewicz <elia@marcinkiewicz.me>
Date: Wed, 6 Mar 2024 21:00:29 +0100
Subject: [PATCH] document manual hash generation

---
 README.md | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/README.md b/README.md
index 87a762d..0c5d364 100644
--- a/README.md
+++ b/README.md
@@ -24,6 +24,22 @@ PN532: No response from PN532!
 $
 ```
 
+## scanning new cards with a phone app
+
+get a phone with nfc and the "nfc tools" app installed, scan card, look for "serial number", get first four bytes of that, use following code:
+
+```
+# assumes card serial number 0x13121337 and pin 2137
+import hashlib
+def generate_hash(card_uid, pin):
+    card_uid = bytes(reversed(card_uid[:4])).hex()
+    s = "{:08x}:{}".format(int(pin), card_uid)
+    hash=hashlib.sha256(s.encode('ascii')).digest().hex()
+    return hash
+
+generate_hash([0x13,0x12,0x13,0x37],bytearray(source=[ord('2'),ord('1'),ord('3'),ord('7')]))
+```
+
 ## syncing data from LDAP
 
 big TODO; currently, you need to: