diff --git a/sim/mcuboot-sys/Cargo.toml b/sim/mcuboot-sys/Cargo.toml
index 7512e22..4f20725 100644
--- a/sim/mcuboot-sys/Cargo.toml
+++ b/sim/mcuboot-sys/Cargo.toml
@@ -21,6 +21,9 @@
 # Verify ECDSA (secp256r1) signatures.
 sig-ecdsa = []
 
+# Verify ED25519 signatures.
+sig-ed25519 = []
+
 # Overwrite only upgrade
 overwrite-only = []
 
diff --git a/sim/mcuboot-sys/build.rs b/sim/mcuboot-sys/build.rs
index ce4ee25..3e419bd 100644
--- a/sim/mcuboot-sys/build.rs
+++ b/sim/mcuboot-sys/build.rs
@@ -12,6 +12,7 @@
     let sig_rsa = env::var("CARGO_FEATURE_SIG_RSA").is_ok();
     let sig_rsa3072 = env::var("CARGO_FEATURE_SIG_RSA3072").is_ok();
     let sig_ecdsa = env::var("CARGO_FEATURE_SIG_ECDSA").is_ok();
+    let sig_ed25519 = env::var("CARGO_FEATURE_SIG_ED25519").is_ok();
     let overwrite_only = env::var("CARGO_FEATURE_OVERWRITE_ONLY").is_ok();
     let validate_primary_slot =
                   env::var("CARGO_FEATURE_VALIDATE_PRIMARY_SLOT").is_ok();
@@ -37,7 +38,7 @@
     }
 
     // Currently no more than one sig type can be used simultaneously.
-    if vec![sig_rsa, sig_rsa3072, sig_ecdsa].iter()
+    if vec![sig_rsa, sig_rsa3072, sig_ecdsa, sig_ed25519].iter()
         .fold(0, |sum, &v| sum + v as i32) > 1 {
         panic!("mcuboot does not support more than one sig type at the same time");
     }
@@ -83,6 +84,18 @@
 
         conf.file("../../ext/mbedtls/src/platform_util.c");
         conf.file("../../ext/mbedtls/src/asn1parse.c");
+    } else if sig_ed25519 {
+        conf.define("MCUBOOT_SIGN_ED25519", None);
+        conf.define("MCUBOOT_USE_MBED_TLS", None);
+
+        conf.include("mbedtls/include");
+        conf.file("mbedtls/library/sha256.c");
+        conf.file("mbedtls/library/sha512.c");
+        conf.file("csupport/keys.c");
+        conf.file("../../ext/fiat/src/curve25519.c");
+        conf.file("mbedtls/library/platform.c");
+        conf.file("mbedtls/library/platform_util.c");
+        conf.file("mbedtls/library/asn1parse.c");
     } else {
         // Neither signature type, only verify sha256. The default
         // configuration file bundled with mbedTLS is sufficient.
@@ -148,6 +161,10 @@
             conf.file("../../ext/tinycrypt/lib/source/aes_encrypt.c");
             conf.file("../../ext/tinycrypt/lib/source/aes_decrypt.c");
         }
+
+        if sig_ed25519 {
+            panic!("ed25519 does not support image encryption with KW yet");
+        }
     }
 
     if sig_rsa && enc_kw {
@@ -156,6 +173,8 @@
         conf.define("MBEDTLS_CONFIG_FILE", Some("<config-rsa.h>"));
     } else if sig_ecdsa && !enc_kw {
         conf.define("MBEDTLS_CONFIG_FILE", Some("<config-asn1.h>"));
+    } else if sig_ed25519 {
+        conf.define("MBEDTLS_CONFIG_FILE", Some("<config-ed25519.h>"));
     } else if enc_kw {
         conf.define("MBEDTLS_CONFIG_FILE", Some("<config-kw.h>"));
     }
@@ -165,6 +184,8 @@
         conf.file("../../boot/bootutil/src/image_rsa.c");
     } else if sig_ecdsa {
         conf.file("../../boot/bootutil/src/image_ec256.c");
+    } else if sig_ed25519 {
+        conf.file("../../boot/bootutil/src/image_ed25519.c");
     }
     conf.file("../../boot/bootutil/src/loader.c");
     conf.file("../../boot/bootutil/src/caps.c");
diff --git a/sim/mcuboot-sys/csupport/keys.c b/sim/mcuboot-sys/csupport/keys.c
index 23bdb21..e0aca05 100644
--- a/sim/mcuboot-sys/csupport/keys.c
+++ b/sim/mcuboot-sys/csupport/keys.c
@@ -122,6 +122,17 @@
     0x8b, 0x68, 0x34, 0xcc, 0x3a, 0x6a, 0xfc, 0x53,
     0x8e, 0xfa, 0xc1, };
 const unsigned int root_pub_der_len = 91;
+#elif defined(MCUBOOT_SIGN_ED25519)
+#define HAVE_KEYS
+const unsigned char root_pub_der[] = {
+    0x30, 0x2a, 0x30, 0x05, 0x06, 0x03, 0x2b, 0x65,
+    0x70, 0x03, 0x21, 0x00, 0xd4, 0xb3, 0x1b, 0xa4,
+    0x9a, 0x3a, 0xdd, 0x3f, 0x82, 0x5d, 0x10, 0xca,
+    0x7f, 0x31, 0xb5, 0x0b, 0x0d, 0xe8, 0x7f, 0x37,
+    0xcc, 0xc4, 0x9f, 0x1a, 0x40, 0x3a, 0x5c, 0x13,
+    0x20, 0xff, 0xb4, 0xe0,
+};
+const unsigned int root_pub_der_len = 44;
 #endif
 
 #if defined(HAVE_KEYS)