From 1ce44fac6bf0f3f1883b8e5f4bb523b791a6c821 Mon Sep 17 00:00:00 2001
From: Yuval Adam <_@yuv.al>
Date: Tue, 23 Feb 2021 00:16:13 +0200
Subject: Clarify hash pitfall and cleanup

---
 README.md | 4 +++-
 verify.py | 3 +--
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/README.md b/README.md
index 57d716f..bec8f8f 100644
--- a/README.md
+++ b/README.md
@@ -22,6 +22,8 @@ Base64EncodedSignature#{"id":"01/IL/ABCD1234ABCD1234ABCD1234ABCD1234#ABCD1234","
 
 Where `Base64EncodedSignature` are 256 bytes of an RSA signature signed with a 2048-bit public key and PKCS#1 v1.5 padding, followed by a `#` delimiter, and then the signed JSON data as defined in https://github.com/MohGovIL/Ramzor#minimal-dataset
 
+Note: **The current MOH implementation has a pitfall.** The JSON data is not signed as is, but rather the **SHA256 hash** of the data is signed.
+
 ### Certificates
 
 The Ministry of Healthy RSA certificate seems to be available at https://ramzorfiles.z6.web.core.windows.net/RamzorQRPubKey.der
@@ -124,7 +126,7 @@ Convert the DER formatted certificate to a PEM file:
 $ openssl x509 -pubkey -noout -inform der -in certs/RamzorQRPubKey.der > certs/RamzorQRPubKey.pem
 ```
 
-Assumed the signed JSON data (without any trailing whitespace) is in `data.json`. Before we verify the data we need to hash the signed JSON (this is likely an implementation error by MOH!):
+Assumed the signed JSON data (without any trailing whitespace) is in `data.json`. Before we verify the data we need to hash the signed JSON:
 
 ```bash
 $ openssl dgst -binary -sha256 data.json > data.hash
diff --git a/verify.py b/verify.py
index 71bc1e1..2336d70 100644
--- a/verify.py
+++ b/verify.py
@@ -1,7 +1,6 @@
 import base64
 
-from cryptography.hazmat.primitives import hashes
-from cryptography.hazmat.primitives import serialization
+from cryptography.hazmat.primitives import hashes, serialization
 from cryptography.hazmat.primitives.asymmetric import padding
 
 sig = base64.b64decode("base64EncodedSignature==")
-- 
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