From 9169f4447e1f36632c20e4291aafee7cc1721216 Mon Sep 17 00:00:00 2001
From: Florian Dold <florian@dold.me>
Date: Wed, 2 Nov 2022 12:36:28 +0100
Subject: [PATCH] age mask clarification

---
 src/include/taler_crypto_lib.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/include/taler_crypto_lib.h b/src/include/taler_crypto_lib.h
index 73b92fe86..4c478cefd 100644
--- a/src/include/taler_crypto_lib.h
+++ b/src/include/taler_crypto_lib.h
@@ -1138,6 +1138,9 @@ struct TALER_BlindedDenominationSignature
  *
  * A value of 0 means that the exchange does not support the extension for
  * age-restriction.
+ *
+ * For a non-0 age mask, the 0th bit always must be set, otherwise the age
+ * mask is considered invalid.
  */
 struct TALER_AgeMask
 {