From cc3a16a8bf25d62ee8f1645949403ade64203152 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Mon, 19 Jan 2026 14:47:31 -1000
Subject: [PATCH] tweak

---
 esphome/components/dsmr/__init__.py | 22 +++-------------------
 esphome/components/dsmr/dsmr.cpp    |  1 +
 esphome/config_validation.py        |  8 ++++----
 3 files changed, 8 insertions(+), 23 deletions(-)

diff --git a/esphome/components/dsmr/__init__.py b/esphome/components/dsmr/__init__.py
index 0ba68daf5d..386da3ce21 100644
--- a/esphome/components/dsmr/__init__.py
+++ b/esphome/components/dsmr/__init__.py
@@ -25,29 +25,13 @@ dsmr_ns = cg.esphome_ns.namespace("esphome::dsmr")
 Dsmr = dsmr_ns.class_("Dsmr", cg.Component, uart.UARTDevice)
 
 
-def _validate_key(value):
-    value = cv.string_strict(value)
-    parts = [value[i : i + 2] for i in range(0, len(value), 2)]
-    if len(parts) != 16:
-        raise cv.Invalid("Decryption key must consist of 16 hexadecimal numbers")
-    parts_int = []
-    if any(len(part) != 2 for part in parts):
-        raise cv.Invalid("Decryption key must be format XX")
-    for part in parts:
-        try:
-            parts_int.append(int(part, 16))
-        except ValueError:
-            # pylint: disable=raise-missing-from
-            raise cv.Invalid("Decryption key must be hex values from 00 to FF")
-
-    return "".join(f"{part:02X}" for part in parts_int)
-
-
 CONFIG_SCHEMA = cv.All(
     cv.Schema(
         {
             cv.GenerateID(): cv.declare_id(Dsmr),
-            cv.Optional(CONF_DECRYPTION_KEY): _validate_key,
+            cv.Optional(CONF_DECRYPTION_KEY): lambda value: cv.bind_key(
+                value, name="Decryption key"
+            ),
             cv.Optional(CONF_CRC_CHECK, default=True): cv.boolean,
             cv.Optional(CONF_GAS_MBUS_ID, default=1): cv.int_,
             cv.Optional(CONF_WATER_MBUS_ID, default=2): cv.int_,
diff --git a/esphome/components/dsmr/dsmr.cpp b/esphome/components/dsmr/dsmr.cpp
index 43016cb468..c78d37bf5e 100644
--- a/esphome/components/dsmr/dsmr.cpp
+++ b/esphome/components/dsmr/dsmr.cpp
@@ -308,6 +308,7 @@ void Dsmr::set_decryption_key(const char *decryption_key) {
 
   if (!parse_hex(decryption_key, this->decryption_key_, 16)) {
     ESP_LOGE(TAG, "Error, decryption key must be 32 hex characters");
+    this->decryption_key_.clear();
     return;
   }
 
diff --git a/esphome/config_validation.py b/esphome/config_validation.py
index 8e2fadbea8..b7ab02013d 100644
--- a/esphome/config_validation.py
+++ b/esphome/config_validation.py
@@ -1046,20 +1046,20 @@ def mac_address(value):
     return core.MACAddress(*parts_int)
 
 
-def bind_key(value):
+def bind_key(value, *, name="Bind key"):
     value = string_strict(value)
     parts = [value[i : i + 2] for i in range(0, len(value), 2)]
     if len(parts) != 16:
-        raise Invalid("Bind key must consist of 16 hexadecimal numbers")
+        raise Invalid(f"{name} must consist of 16 hexadecimal numbers")
     parts_int = []
     if any(len(part) != 2 for part in parts):
-        raise Invalid("Bind key must be format XX")
+        raise Invalid(f"{name} must be format XX")
     for part in parts:
         try:
             parts_int.append(int(part, 16))
         except ValueError:
             # pylint: disable=raise-missing-from
-            raise Invalid("Bind key must be hex values from 00 to FF")
+            raise Invalid(f"{name} must be hex values from 00 to FF")
 
     return "".join(f"{part:02X}" for part in parts_int)