diff --git a/boot/zephyr/include/config-asn1.h b/boot/zephyr/include/config-asn1.h
new file mode 100644
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--- /dev/null
+++ b/boot/zephyr/include/config-asn1.h
@@ -0,0 +1,47 @@
+/*
+ *  Configuration of mbedTLS containing only the ASN.1 parser.
+ *
+ *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
+ *  Copyright (C) 2016, Linaro Ltd
+ *  SPDX-License-Identifier: Apache-2.0
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License"); you may
+ *  not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ *
+ *  This file is part of mbed TLS (https://tls.mbed.org)
+ */
+
+/*
+ * Minimal configuration for using TLS in the bootloader
+ *
+ * - RSA or ECDSA signature verification
+ */
+
+#ifndef MBEDTLS_CONFIG_H
+#define MBEDTLS_CONFIG_H
+
+#define MBEDTLS_PLATFORM_C
+#define MBEDTLS_PLATFORM_MEMORY
+#define MBEDTLS_MEMORY_BUFFER_ALLOC_C
+#define MBEDTLS_PLATFORM_NO_STD_FUNCTIONS
+
+/* mbed TLS modules */
+#define MBEDTLS_ASN1_PARSE_C
+// #define MBEDTLS_ASN1_WRITE_C
+// #define MBEDTLS_BIGNUM_C
+// #define MBEDTLS_MD_C
+// #define MBEDTLS_OID_C
+#define MBEDTLS_SHA256_C
+
+#include "mbedtls/check_config.h"
+
+#endif /* MBEDTLS_CONFIG_H */