diff --git a/boot/zephyr/Kconfig b/boot/zephyr/Kconfig
index 0cf133a..a52c7d6 100644
--- a/boot/zephyr/Kconfig
+++ b/boot/zephyr/Kconfig
@@ -126,6 +126,10 @@
 
 config BOOT_SIGNATURE_KEY_FILE
 	string "PEM key file"
+	default "root-ec-p256.pem" if BOOT_SIGNATURE_TYPE_ECDSA_P256
+	default "root-ed25519.pem" if BOOT_SIGNATURE_TYPE_ED25519
+	default "root-rsa-3072.pem" if BOOT_SIGNATURE_TYPE_RSA && BOOT_SIGNATURE_TYPE_RSA_LEN=3072
+	default "root-rsa-2048.pem" if BOOT_SIGNATURE_TYPE_RSA && BOOT_SIGNATURE_TYPE_RSA_LEN=2048
 	default ""
 	help
 	  You can use either absolute or relative path.
diff --git a/boot/zephyr/prj.conf b/boot/zephyr/prj.conf
index 17826db..7f15372 100644
--- a/boot/zephyr/prj.conf
+++ b/boot/zephyr/prj.conf
@@ -14,22 +14,6 @@
 CONFIG_BOOT_UPGRADE_ONLY=n
 CONFIG_BOOT_BOOTSTRAP=n
 
-### Default to RSA
-CONFIG_BOOT_SIGNATURE_TYPE_NONE=n
-CONFIG_BOOT_SIGNATURE_TYPE_RSA=y
-CONFIG_BOOT_SIGNATURE_TYPE_RSA_LEN=2048
-CONFIG_BOOT_SIGNATURE_TYPE_ECDSA_P256=n
-CONFIG_BOOT_SIGNATURE_TYPE_ED25519=n
-
-### The bootloader generates its own signature verification based on a
-### key file which needs to be provided and needs to match the selected signing
-### algorithm (CONFIG_BOOT_SIGNATURE_TYPE_).
-### The PEM files below are provided as examples.
-CONFIG_BOOT_SIGNATURE_KEY_FILE="root-rsa-2048.pem"
-#CONFIG_BOOT_SIGNATURE_KEY_FILE="root-rsa-3072.pem"
-#CONFIG_BOOT_SIGNATURE_KEY_FILE="root-ec-p256.pem"
-#CONFIG_BOOT_SIGNATURE_KEY_FILE="root-ed25519.pem"
-
 ### mbedTLS has its own heap
 # CONFIG_HEAP_MEM_POOL_SIZE is not set