diff --git a/Cargo.lock b/Cargo.lock
index ba71f18..93595d1 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1,20 +1,5 @@
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
-[[package]]
-name = "addr2line"
-version = "0.14.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a55f82cfe485775d02112886f4169bde0c5894d75e79ead7eafe7e40a25e45f7"
-dependencies = [
- "gimli",
-]
-
-[[package]]
-name = "adler"
-version = "0.2.3"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ee2a4ec343196209d6594e19543ae87a39f96d5534d7174822a3ad825dd6ed7e"
-
 [[package]]
 name = "aes"
 version = "0.4.0"
@@ -85,26 +70,6 @@ dependencies = [
  "winapi",
 ]
 
-[[package]]
-name = "autocfg"
-version = "1.0.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "cdb031dd78e28731d87d56cc8ffef4a8f36ca26c38fe2de700543e627f8a464a"
-
-[[package]]
-name = "backtrace"
-version = "0.3.55"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ef5140344c85b01f9bbb4d4b7288a8aa4b3287ccef913a14bcc78a1063623598"
-dependencies = [
- "addr2line",
- "cfg-if 1.0.0",
- "libc",
- "miniz_oxide",
- "object",
- "rustc-demangle",
-]
-
 [[package]]
 name = "base64"
 version = "0.12.3"
@@ -280,7 +245,6 @@ dependencies = [
  "cbindgen",
  "dart-bindgen",
  "dup-crypto",
- "ffi_helpers",
  "thiserror",
 ]
 
@@ -306,39 +270,6 @@ dependencies = [
  "zeroize",
 ]
 
-[[package]]
-name = "failure"
-version = "0.1.8"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d32e9bd16cc02eae7db7ef620b392808b89f6a5e16bb3497d159c6b92a0f4f86"
-dependencies = [
- "backtrace",
- "failure_derive",
-]
-
-[[package]]
-name = "failure_derive"
-version = "0.1.8"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "aa4da3c766cd7a0db8242e326e9e4e081edd567072893ed320008189715366a4"
-dependencies = [
- "proc-macro2",
- "quote",
- "syn",
- "synstructure",
-]
-
-[[package]]
-name = "ffi_helpers"
-version = "0.2.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "36a21261040ffbc3999698b39170d6e951f2823dd9ad7b50469309156060a50c"
-dependencies = [
- "failure",
- "failure_derive",
- "libc",
-]
-
 [[package]]
 name = "generic-array"
 version = "0.14.4"
@@ -362,12 +293,6 @@ dependencies = [
  "wasm-bindgen",
 ]
 
-[[package]]
-name = "gimli"
-version = "0.23.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f6503fe142514ca4799d4c26297c4248239fe8838d827db6bd6065c6ed29a6ce"
-
 [[package]]
 name = "glob"
 version = "0.3.0"
@@ -428,22 +353,6 @@ dependencies = [
  "cfg-if 0.1.10",
 ]
 
-[[package]]
-name = "miniz_oxide"
-version = "0.4.3"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0f2d26ec3309788e423cfbf68ad1800f061638098d76a83681af979dc4eda19d"
-dependencies = [
- "adler",
- "autocfg",
-]
-
-[[package]]
-name = "object"
-version = "0.22.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8d3b63360ec3cb337817c2dbd47ab4a0f170d285d8e5a2064600f3def1402397"
-
 [[package]]
 name = "once_cell"
 version = "1.5.2"
@@ -551,12 +460,6 @@ dependencies = [
  "winapi",
 ]
 
-[[package]]
-name = "rustc-demangle"
-version = "0.1.18"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6e3bad0ee36814ca07d7968269dd4b7ec89ec2da10c4bb613928d3077083c232"
-
 [[package]]
 name = "ryu"
 version = "1.0.5"
diff --git a/native/dubp_rs/Cargo.toml b/native/dubp_rs/Cargo.toml
index c3d7073..feeb05b 100644
--- a/native/dubp_rs/Cargo.toml
+++ b/native/dubp_rs/Cargo.toml
@@ -11,7 +11,6 @@ crate-type = ["rlib"]
 [dependencies]
 allo-isolate = "0.1.6"
 dup-crypto = { version = "0.36.0", features = ["dewif", "mnemonic", "mnemonic_french", "rand", "scrypt"] }
-ffi_helpers = "0.2"
 thiserror = "1.0.23"
 
 [build-dependencies]
diff --git a/native/dubp_rs/src/dewif.rs b/native/dubp_rs/src/dewif.rs
index 372db6e..7d07565 100644
--- a/native/dubp_rs/src/dewif.rs
+++ b/native/dubp_rs/src/dewif.rs
@@ -35,11 +35,16 @@ pub(super) fn gen_pin10() -> Result<String, DubpError> {
 }
 
 pub(super) fn change_pin(
-    currency: &str,
-    dewif: &str,
-    old_pin: &str,
-    new_pin: &str,
+    currency: *const raw::c_char,
+    dewif: *const raw::c_char,
+    old_pin: *const raw::c_char,
+    new_pin: *const raw::c_char,
 ) -> Result<String, DubpError> {
+    let currency = char_ptr_to_str(currency)?;
+    let dewif = char_ptr_to_str(dewif)?;
+    let old_pin = char_ptr_to_str(old_pin)?;
+    let new_pin = char_ptr_to_str(new_pin)?;
+
     let currency = parse_currency(currency)?;
     let mut keypairs = dup_crypto::dewif::read_dewif_file_content(
         ExpectedCurrency::Specific(currency),
@@ -57,11 +62,15 @@ pub(super) fn change_pin(
 }
 
 pub(super) fn gen_dewif(
-    currency: &str,
+    currency: *const raw::c_char,
     language: u32,
-    mnemonic: &str,
-    pin: &str,
+    mnemonic: *const raw::c_char,
+    pin: *const raw::c_char,
 ) -> Result<String, DubpError> {
+    let currency = char_ptr_to_str(currency)?;
+    let mnemonic = char_ptr_to_str(mnemonic)?;
+    let pin = char_ptr_to_str(pin)?;
+
     let currency = parse_currency(currency)?;
     let mnemonic = Mnemonic::from_phrase(mnemonic, u32_to_language(language)?)
         .map_err(|_| DubpError::WrongLanguage)?;
@@ -72,12 +81,20 @@ pub(super) fn gen_dewif(
     ))
 }
 
-pub(super) fn get_pubkey(currency: &str, dewif: &str, pin: &str) -> Result<String, DubpError> {
+pub(super) fn get_pubkey(
+    currency: *const raw::c_char,
+    dewif: *const raw::c_char,
+    pin: *const raw::c_char,
+) -> Result<String, DubpError> {
+    let currency = char_ptr_to_str(currency)?;
+    let dewif = char_ptr_to_str(dewif)?;
+    let pin = char_ptr_to_str(pin)?;
+
     let currency = parse_currency(currency)?;
     let mut keypairs = dup_crypto::dewif::read_dewif_file_content(
         ExpectedCurrency::Specific(currency),
         dewif,
-        &pin,
+        &pin.to_ascii_uppercase(),
     )
     .map_err(DubpError::DewifReadError)?;
     if let Some(KeyPairEnum::Ed25519(keypair)) = keypairs.next() {
@@ -87,12 +104,22 @@ pub(super) fn get_pubkey(currency: &str, dewif: &str, pin: &str) -> Result<Strin
     }
 }
 
-pub(super) fn sign(currency: &str, dewif: &str, pin: &str, msg: &str) -> Result<String, DubpError> {
+pub(super) fn sign(
+    currency: *const raw::c_char,
+    dewif: *const raw::c_char,
+    pin: *const raw::c_char,
+    msg: *const raw::c_char,
+) -> Result<String, DubpError> {
+    let currency = char_ptr_to_str(currency)?;
+    let dewif = char_ptr_to_str(dewif)?;
+    let pin = char_ptr_to_str(pin)?;
+    let msg = char_ptr_to_str(msg)?;
+
     let currency = parse_currency(currency)?;
     let mut keypairs = dup_crypto::dewif::read_dewif_file_content(
         ExpectedCurrency::Specific(currency),
         dewif,
-        &pin,
+        &pin.to_ascii_uppercase(),
     )
     .map_err(DubpError::DewifReadError)?;
     if let Some(KeyPairEnum::Ed25519(keypair)) = keypairs.next() {
@@ -103,16 +130,27 @@ pub(super) fn sign(currency: &str, dewif: &str, pin: &str, msg: &str) -> Result<
 }
 
 pub(super) fn sign_several(
-    currency: &str,
-    dewif: &str,
-    pin: &str,
-    msgs: &[&str],
+    currency: *const raw::c_char,
+    dewif: *const raw::c_char,
+    pin: *const raw::c_char,
+    msgs_len: usize,
+    msgs: *const *const raw::c_char,
 ) -> Result<Vec<String>, DubpError> {
+    let currency = char_ptr_to_str(currency)?;
+    let dewif = char_ptr_to_str(dewif)?;
+    let pin = char_ptr_to_str(pin)?;
+
+    let msgs_slice: &[*const raw::c_char] = unsafe { std::slice::from_raw_parts(msgs, msgs_len) };
+    let mut msgs = Vec::with_capacity(msgs_len);
+    for ptr_c_char in msgs_slice {
+        msgs.push(char_ptr_to_str(*ptr_c_char)?);
+    }
+
     let currency = parse_currency(currency)?;
     let mut keypairs = dup_crypto::dewif::read_dewif_file_content(
         ExpectedCurrency::Specific(currency),
         dewif,
-        &pin,
+        &pin.to_ascii_uppercase(),
     )
     .map_err(DubpError::DewifReadError)?;
     if let Some(KeyPairEnum::Ed25519(keypair)) = keypairs.next() {
diff --git a/native/dubp_rs/src/lib.rs b/native/dubp_rs/src/lib.rs
index ae1a4a7..8d2f03a 100644
--- a/native/dubp_rs/src/lib.rs
+++ b/native/dubp_rs/src/lib.rs
@@ -18,7 +18,7 @@
 mod dewif;
 mod mnemonic;
 
-use allo_isolate::Isolate;
+use allo_isolate::{IntoDart, Isolate};
 use dup_crypto::{
     bases::b58::ToBase58,
     dewif::{Currency, DewifReadError, ExpectedCurrency, G1_CURRENCY, G1_TEST_CURRENCY},
@@ -28,7 +28,6 @@ use dup_crypto::{
     },
     mnemonic::{Language, Mnemonic, MnemonicType},
 };
-use ffi_helpers::null_pointer_check;
 use std::{ffi::CStr, io, os::raw};
 use thiserror::Error;
 
@@ -39,12 +38,16 @@ pub enum DubpError {
     DewifReadError(DewifReadError),
     #[error("I/O error: {0}")]
     IoErr(io::Error),
+    #[error("A given parameter is null")]
+    NullParamErr,
     #[error("fail to generate random bytes")]
     RandErr,
     #[error("Unknown currency name")]
     UnknownCurrencyName,
     #[error("Unknown language")]
     UnknownLanguage,
+    #[error("{0}")]
+    Utf8Error(std::str::Utf8Error),
     #[error("Wrong language")]
     WrongLanguage,
 }
@@ -55,39 +58,41 @@ impl From<io::Error> for DubpError {
     }
 }
 
-macro_rules! error {
-    ($result:expr) => {
-        error!($result, 0);
-    };
-    ($result:expr, $error:expr) => {
-        match $result {
-            Ok(value) => value,
-            Err(e) => {
-                ffi_helpers::update_last_error(e);
-                return $error;
-            }
+struct DartRes(allo_isolate::ffi::DartCObject);
+impl IntoDart for DartRes {
+    fn into_dart(self) -> allo_isolate::ffi::DartCObject {
+        self.0.into_dart()
+    }
+}
+impl<E> From<Result<String, E>> for DartRes
+where
+    E: ToString,
+{
+    fn from(res: Result<String, E>) -> Self {
+        match res {
+            Ok(string) => Self(vec![string].into_dart()),
+            Err(e) => Self(vec![String::from("_"), e.to_string()].into_dart()),
         }
-    };
+    }
+}
+impl<E> From<Result<Vec<String>, E>> for DartRes
+where
+    E: ToString,
+{
+    fn from(res: Result<Vec<String>, E>) -> Self {
+        match res {
+            Ok(vec_string) => Self(vec_string.into_dart()),
+            Err(e) => Self(vec![String::with_capacity(0), e.to_string()].into_dart()),
+        }
+    }
 }
 
-macro_rules! cstr {
-    ($ptr:expr) => {
-        cstr!($ptr, 0);
-    };
-    ($ptr:expr, $error:expr) => {{
-        null_pointer_check!($ptr);
-        error!(unsafe { CStr::from_ptr($ptr).to_str() }, $error)
-    }};
-}
-
-#[no_mangle]
-pub unsafe extern "C" fn last_error_length() -> i32 {
-    ffi_helpers::error_handling::last_error_length()
-}
-
-#[no_mangle]
-pub unsafe extern "C" fn error_message_utf8(buf: *mut raw::c_char, length: i32) -> i32 {
-    ffi_helpers::error_handling::error_message_utf8(buf, length)
+pub(crate) fn char_ptr_to_str<'a>(c_char_ptr: *const raw::c_char) -> Result<&'a str, DubpError> {
+    if c_char_ptr.is_null() {
+        Err(DubpError::NullParamErr)
+    } else {
+        unsafe { CStr::from_ptr(c_char_ptr).to_str() }.map_err(DubpError::Utf8Error)
+    }
 }
 
 #[no_mangle]
@@ -97,13 +102,10 @@ pub extern "C" fn change_dewif_pin(
     dewif: *const raw::c_char,
     old_pin: *const raw::c_char,
     new_pin: *const raw::c_char,
-) -> i32 {
-    let currency = cstr!(currency);
-    let dewif = cstr!(dewif);
-    let old_pin = cstr!(old_pin);
-    let new_pin = cstr!(new_pin);
-    Isolate::new(port).post(error!(dewif::change_pin(currency, dewif, old_pin, new_pin)));
-    1
+) {
+    Isolate::new(port).post(DartRes::from(dewif::change_pin(
+        currency, dewif, old_pin, new_pin,
+    )));
 }
 
 #[no_mangle]
@@ -113,36 +115,30 @@ pub extern "C" fn gen_dewif(
     language: u32,
     mnemonic: *const raw::c_char,
     pin: *const raw::c_char,
-) -> i32 {
-    let currency = cstr!(currency);
-    let mnemonic = cstr!(mnemonic);
-    let pin = cstr!(pin);
-    Isolate::new(port).post(error!(dewif::gen_dewif(currency, language, mnemonic, pin)));
-    1
+) {
+    Isolate::new(port).post(DartRes::from(dewif::gen_dewif(
+        currency, language, mnemonic, pin,
+    )));
 }
 
 #[no_mangle]
-pub extern "C" fn gen_mnemonic(port: i64, language: u32) -> i32 {
-    Isolate::new(port).post(error!(mnemonic::gen_mnemonic(language)));
-    1
+pub extern "C" fn gen_mnemonic(port: i64, language: u32) {
+    Isolate::new(port).post(DartRes::from(mnemonic::gen_mnemonic(language)));
 }
 
 #[no_mangle]
-pub extern "C" fn gen_pin6(port: i64) -> i32 {
-    Isolate::new(port).post(error!(dewif::gen_pin6()));
-    1
+pub extern "C" fn gen_pin6(port: i64) {
+    Isolate::new(port).post(DartRes::from(dewif::gen_pin6()));
 }
 
 #[no_mangle]
-pub extern "C" fn gen_pin8(port: i64) -> i32 {
-    Isolate::new(port).post(error!(dewif::gen_pin8()));
-    1
+pub extern "C" fn gen_pin8(port: i64) {
+    Isolate::new(port).post(DartRes::from(dewif::gen_pin8()));
 }
 
 #[no_mangle]
-pub extern "C" fn gen_pin10(port: i64) -> i32 {
-    Isolate::new(port).post(error!(dewif::gen_pin10()));
-    1
+pub extern "C" fn gen_pin10(port: i64) {
+    Isolate::new(port).post(DartRes::from(dewif::gen_pin10()));
 }
 
 #[no_mangle]
@@ -151,16 +147,8 @@ pub extern "C" fn get_dewif_pubkey(
     currency: *const raw::c_char,
     dewif: *const raw::c_char,
     pin: *const raw::c_char,
-) -> i32 {
-    let currency = cstr!(currency);
-    let dewif = cstr!(dewif);
-    let pin = cstr!(pin);
-    Isolate::new(port).post(error!(dewif::get_pubkey(
-        currency,
-        dewif,
-        &pin.to_ascii_uppercase()
-    )));
-    1
+) {
+    Isolate::new(port).post(DartRes::from(dewif::get_pubkey(currency, dewif, pin)));
 }
 
 #[no_mangle]
@@ -168,13 +156,11 @@ pub extern "C" fn mnemonic_to_pubkey(
     port: i64,
     language: u32,
     mnemonic_phrase: *const raw::c_char,
-) -> i32 {
-    let mnemonic_phrase = cstr!(mnemonic_phrase);
-    Isolate::new(port).post(error!(mnemonic::mnemonic_to_pubkey(
+) {
+    Isolate::new(port).post(DartRes::from(mnemonic::mnemonic_to_pubkey(
         language,
-        mnemonic_phrase
+        mnemonic_phrase,
     )));
-    1
 }
 
 #[no_mangle]
@@ -184,18 +170,8 @@ pub extern "C" fn sign(
     dewif: *const raw::c_char,
     pin: *const raw::c_char,
     msg: *const raw::c_char,
-) -> i32 {
-    let currency = cstr!(currency);
-    let dewif = cstr!(dewif);
-    let pin = cstr!(pin);
-    let msg = cstr!(msg);
-    Isolate::new(port).post(error!(dewif::sign(
-        currency,
-        dewif,
-        &pin.to_ascii_uppercase(),
-        msg
-    )));
-    1
+) {
+    Isolate::new(port).post(DartRes::from(dewif::sign(currency, dewif, pin, msg)));
 }
 
 #[no_mangle]
@@ -206,24 +182,8 @@ pub extern "C" fn sign_several(
     pin: *const raw::c_char,
     msgs_len: usize,
     msgs: *const *const raw::c_char,
-) -> i32 {
-    let currency = cstr!(currency);
-    let dewif = cstr!(dewif);
-    let pin = cstr!(pin);
-
-    let msgs_slice: &[*const raw::c_char] = unsafe { std::slice::from_raw_parts(msgs, msgs_len) };
-    let mut vec = Vec::with_capacity(msgs_len);
-    for ptr_c_char in msgs_slice {
-        vec.push(cstr!(*ptr_c_char));
-    }
-
-    Isolate::new(port).post(error!(dewif::sign_several(
-        currency,
-        dewif,
-        &pin.to_ascii_uppercase(),
-        &vec
-    )));
-    1
+) {
+    Isolate::new(port).post(dewif::sign_several(currency, dewif, pin, msgs_len, msgs));
 }
 
 fn u32_to_language(i: u32) -> Result<Language, DubpError> {
diff --git a/native/dubp_rs/src/mnemonic.rs b/native/dubp_rs/src/mnemonic.rs
index 765427d..ac17486 100644
--- a/native/dubp_rs/src/mnemonic.rs
+++ b/native/dubp_rs/src/mnemonic.rs
@@ -21,7 +21,12 @@ pub(super) fn gen_mnemonic(language: u32) -> Result<String, DubpError> {
     Ok(mnemonic.phrase().to_owned())
 }
 
-pub(super) fn mnemonic_to_pubkey(language: u32, mnemonic: &str) -> Result<String, DubpError> {
+pub(super) fn mnemonic_to_pubkey(
+    language: u32,
+    mnemonic: *const raw::c_char,
+) -> Result<String, DubpError> {
+    let mnemonic = char_ptr_to_str(mnemonic)?;
+
     let mnemonic = Mnemonic::from_phrase(mnemonic, u32_to_language(language)?)
         .map_err(|_| DubpError::WrongLanguage)?;
     let seed = dup_crypto::mnemonic::mnemonic_to_seed(&mnemonic);
diff --git a/packages/dubp_rs/lib/dubp.dart b/packages/dubp_rs/lib/dubp.dart
index 0d96d5b..a3384e8 100644
--- a/packages/dubp_rs/lib/dubp.dart
+++ b/packages/dubp_rs/lib/dubp.dart
@@ -54,45 +54,35 @@ class DubpRust {
   /// Generate a random mnemonic
   static Future<String> genMnemonic({Language language = Language.english}) {
     final completer = Completer<String>();
-    final sendPort = singleCompletePort<String, String>(completer);
-    final res = native.gen_mnemonic(
+    final sendPort =
+        singleCompletePort<String, List>(completer, callback: _handleErr);
+    native.gen_mnemonic(
       sendPort.nativePort,
       language.index,
     );
-    if (res != 1) {
-      _throwError();
-    }
     return completer.future;
   }
 
   static Future<String> _genPin(PinLength pinLength) {
     final completer = Completer<String>();
-    final sendPort = singleCompletePort<String, String>(completer);
+    final sendPort =
+        singleCompletePort<String, List>(completer, callback: _handleErr);
     switch (pinLength) {
       case PinLength.ten:
-        final res = native.gen_pin10(
+        native.gen_pin10(
           sendPort.nativePort,
         );
-        if (res != 1) {
-          DubpRust._throwError();
-        }
         break;
       case PinLength.eight:
-        final res = native.gen_pin8(
+        native.gen_pin8(
           sendPort.nativePort,
         );
-        if (res != 1) {
-          DubpRust._throwError();
-        }
         break;
       case PinLength.six:
       default:
-        final res = native.gen_pin6(
+        native.gen_pin6(
           sendPort.nativePort,
         );
-        if (res != 1) {
-          DubpRust._throwError();
-        }
         break;
     }
     return completer.future;
@@ -110,33 +100,29 @@ class DubpRust {
     String newDewif;
     {
       final completer = Completer<String>();
-      final sendPort = singleCompletePort<String, String>(completer);
-      final res = native.change_dewif_pin(
+      final sendPort =
+          singleCompletePort<String, List>(completer, callback: _handleErr);
+      native.change_dewif_pin(
         sendPort.nativePort,
         Utf8.toUtf8(currency),
         Utf8.toUtf8(dewif),
         Utf8.toUtf8(oldPin),
         Utf8.toUtf8(newPin),
       );
-      if (res != 1) {
-        DubpRust._throwError();
-      }
       newDewif = await completer.future;
     }
     // publicKey
     String publicKey;
     {
       final completer = Completer<String>();
-      final sendPort = singleCompletePort<String, String>(completer);
-      final res = native.get_dewif_pubkey(
+      final sendPort =
+          singleCompletePort<String, List>(completer, callback: _handleErr);
+      native.get_dewif_pubkey(
         sendPort.nativePort,
         Utf8.toUtf8(currency),
         Utf8.toUtf8(newDewif),
         Utf8.toUtf8(newPin),
       );
-      if (res != 1) {
-        _throwError();
-      }
       publicKey = await completer.future;
     }
 
@@ -161,32 +147,28 @@ class DubpRust {
     String publicKey;
     {
       final completer = Completer<String>();
-      final sendPort = singleCompletePort<String, String>(completer);
-      final res = native.mnemonic_to_pubkey(
+      final sendPort =
+          singleCompletePort<String, List>(completer, callback: _handleErr);
+      native.mnemonic_to_pubkey(
         sendPort.nativePort,
         language.index,
         Utf8.toUtf8(mnemonic),
       );
-      if (res != 1) {
-        DubpRust._throwError();
-      }
       publicKey = await completer.future;
     }
     // dewif
     String dewif;
     {
       final completer = Completer<String>();
-      final sendPort = singleCompletePort<String, String>(completer);
-      final res = native.gen_dewif(
+      final sendPort =
+          singleCompletePort<String, List>(completer, callback: _handleErr);
+      native.gen_dewif(
         sendPort.nativePort,
         Utf8.toUtf8(currency),
         language.index,
         Utf8.toUtf8(mnemonic),
         Utf8.toUtf8(pin),
       );
-      if (res != 1) {
-        DubpRust._throwError();
-      }
       dewif = await completer.future;
     }
     return Future.value(NewWallet._(dewif, pin, publicKey));
@@ -194,18 +176,16 @@ class DubpRust {
 
   /// Get pulblic key (in base 58) of `dewif` keypair.
   static Future<String> getDewifPublicKey(
-      {String currency = "g1", String dewif, String pin}) {
+      {String currency = "g1", String dewif, String pin}) async {
     final completer = Completer<String>();
-    final sendPort = singleCompletePort<String, String>(completer);
-    final res = native.get_dewif_pubkey(
+    final sendPort =
+        singleCompletePort<String, List>(completer, callback: _handleErr);
+    native.get_dewif_pubkey(
       sendPort.nativePort,
       Utf8.toUtf8(currency),
       Utf8.toUtf8(dewif),
       Utf8.toUtf8(pin),
     );
-    if (res != 1) {
-      _throwError();
-    }
     return completer.future;
   }
 
@@ -215,17 +195,15 @@ class DubpRust {
   static Future<String> sign(
       {String currency = "g1", String dewif, String pin, String message}) {
     final completer = Completer<String>();
-    final sendPort = singleCompletePort<String, String>(completer);
-    final res = native.sign(
+    final sendPort =
+        singleCompletePort<String, List>(completer, callback: _handleErr);
+    native.sign(
       sendPort.nativePort,
       Utf8.toUtf8(currency),
       Utf8.toUtf8(dewif),
       Utf8.toUtf8(pin),
       Utf8.toUtf8(message),
     );
-    if (res != 1) {
-      _throwError();
-    }
     return completer.future;
   }
 
@@ -241,9 +219,10 @@ class DubpRust {
       String pin,
       List<String> messages}) {
     final completer = Completer<List<String>>();
-    final sendPort = singleCompletePort<List<String>, List<String>>(completer);
+    final sendPort = singleCompletePort<List<String>, List>(completer,
+        callback: _handleErrList);
 
-    final res = native.sign_several(
+    native.sign_several(
       sendPort.nativePort,
       Utf8.toUtf8(currency),
       Utf8.toUtf8(dewif),
@@ -251,9 +230,7 @@ class DubpRust {
       messages.length,
       _listStringToPtr(messages),
     );
-    if (res != 1) {
-      _throwError();
-    }
+
     return completer.future;
   }
 
@@ -266,12 +243,25 @@ class DubpRust {
     return ptr;
   }
 
-  static void _throwError() {
-    final length = native.last_error_length();
-    final Pointer<Utf8> message = allocate(count: length);
-    native.error_message_utf8(message, length);
-    final error = Utf8.fromUtf8(message);
-    print(error);
-    throw error;
+  static String _handleErr(List res) {
+    final List<String> arr = res.cast();
+    if (arr.length == 1) {
+      return arr[0];
+    } else {
+      final error = arr[1];
+      print(error);
+      throw error;
+    }
+  }
+
+  static List<String> _handleErrList(List res) {
+    final List<String> arr = res.cast();
+    if (arr.isNotEmpty && arr[0].isEmpty) {
+      final error = arr[1];
+      print(error);
+      throw error;
+    } else {
+      return arr;
+    }
   }
 }