diff --git a/boot/zephyr/include/config-boot.h b/boot/zephyr/include/config-rsa.h
similarity index 80%
rename from boot/zephyr/include/config-boot.h
rename to boot/zephyr/include/config-rsa.h
index 50bee10..3b5c1f5 100644
--- a/boot/zephyr/include/config-boot.h
+++ b/boot/zephyr/include/config-rsa.h
@@ -26,8 +26,8 @@
  * - RSA or ECDSA signature verification
  */
 
-#ifndef MBEDTLS_CONFIG_BOOT_H
-#define MBEDTLS_CONFIG_BOOT_H
+#ifndef MCUBOOT_MBEDTLS_CONFIG_RSA
+#define MCUBOOT_MBEDTLS_CONFIG_RSA
 
 #ifdef CONFIG_MCUBOOT_SERIAL
 /* Mcuboot uses mbedts-base64 for serial protocol encoding. */
@@ -56,20 +56,8 @@
 #define MBEDTLS_TEST_NULL_ENTROPY
 #endif
 
-/* mbed TLS feature support */
-#ifdef MCUBOOT_SIGN_EC
-#define MBEDTLS_ECP_DP_SECP256R1_ENABLED
-#define MBEDTLS_ECP_DP_SECP224R1_ENABLED
-#define MBEDTLS_ECP_NIST_OPTIM
-#define MBEDTLS_ECDSA_C
-#define MBEDTLS_ECDH_C
-#define MBEDTLS_ECP_C
-#endif
-
-#ifdef MCUBOOT_SIGN_RSA
 #define MBEDTLS_RSA_C
 #define MBEDTLS_PKCS1_V21
-#endif
 
 /* mbed TLS modules */
 #define MBEDTLS_ASN1_PARSE_C
@@ -80,13 +68,8 @@
 #define MBEDTLS_SHA256_C
 
 /* Save RAM by adjusting to our exact needs */
-#ifdef MCUBOOT_SIGN_RSA
 #define MBEDTLS_ECP_MAX_BITS             2048
 #define MBEDTLS_MPI_MAX_SIZE              256
-#else
-#define MBEDTLS_ECP_MAX_BITS             256
-#define MBEDTLS_MPI_MAX_SIZE              32 // 256 bits is 32 bytes
-#endif
 
 #define MBEDTLS_SSL_MAX_CONTENT_LEN 1024
 
@@ -95,4 +78,4 @@
 
 #include "mbedtls/check_config.h"
 
-#endif /* MBEDTLS_CONFIG_BOOT_H */
+#endif /* MCUBOOT_MBEDTLS_CONFIG_RSA */
diff --git a/boot/zephyr/include/mcuboot-mbedtls-cfg.h b/boot/zephyr/include/mcuboot-mbedtls-cfg.h
new file mode 100644
index 0000000..14cd9eb
--- /dev/null
+++ b/boot/zephyr/include/mcuboot-mbedtls-cfg.h
@@ -0,0 +1,32 @@
+/*
+ *  Copyright (C) 2018 Open Source Foundries Limited
+ *  SPDX-License-Identifier: Apache-2.0
+ */
+
+#ifndef _MCUBOOT_MBEDTLS_CONFIG_
+#define _MCUBOOT_MBEDTLS_CONFIG_
+
+/**
+ * @file
+ *
+ * This is the top-level mbedTLS configuration file for MCUboot. The
+ * configuration depends on the signature type, so this file just
+ * pulls in the right header depending on that setting.
+ */
+
+/*
+ * IMPORTANT:
+ *
+ * If you put any "generic" definitions in here, make sure to update
+ * the simulator build.rs accordingly.
+ */
+
+#ifdef CONFIG_BOOT_SIGNATURE_TYPE_RSA
+#include "config-rsa.h"
+#elif defined(CONFIG_BOOT_SIGNATURE_TYPE_ECDSA_P256)
+#include "config-asn1.h"
+#else
+#error "Cannot configure mbedTLS; signature type is unknown."
+#endif
+
+#endif
diff --git a/boot/zephyr/include/mcuboot_config/mcuboot_config.h b/boot/zephyr/include/mcuboot_config/mcuboot_config.h
index d7d141d..03d1e37 100644
--- a/boot/zephyr/include/mcuboot_config/mcuboot_config.h
+++ b/boot/zephyr/include/mcuboot_config/mcuboot_config.h
@@ -18,9 +18,17 @@
  */
 #ifndef __BOOTSIM__
 
-/*
- * Initially blank.
- */
+#ifdef CONFIG_BOOT_SIGNATURE_TYPE_RSA
+#define MCUBOOT_SIGN_RSA
+#elif defined(CONFIG_BOOT_SIGNATURE_TYPE_ECDSA_P256)
+#define MCUBOOT_SIGN_EC256
+#endif
+
+#ifdef CONFIG_BOOT_USE_MBEDTLS
+#define MCUBOOT_USE_MBED_TLS
+#elif defined(CONFIG_BOOT_USE_TINYCRYPT)
+#define MCUBOOT_USE_TINYCRYPT
+#endif
 
 #endif /* !__BOOTSIM__ */