diff --git a/src/aleph/sdk/chains/common.py b/src/aleph/sdk/chains/common.py
index 140f5c2d..8113bd3a 100644
--- a/src/aleph/sdk/chains/common.py
+++ b/src/aleph/sdk/chains/common.py
@@ -62,7 +62,6 @@ def _setup_sender(self, message: Dict) -> Dict:
         else:
             raise ValueError("Message sender does not match the account's public key.")
 
-    @abstractmethod
     async def sign_message(self, message: Dict) -> Dict:
         """
         Returns a signed message from an Aleph message.
@@ -72,19 +71,19 @@ async def sign_message(self, message: Dict) -> Dict:
             Dict: Signed message
         """
         message = self._setup_sender(message)
-        sig = await self.sign_raw(get_verification_buffer(message))
-        message["signature"] = sig.hex()
+        message["signature"] = await self.sign_raw(get_verification_buffer(message))
         return message
-    
-    async def sign_raw(self, buffer: bytes) -> bytes:
+
+    @abstractmethod
+    async def sign_raw(self, buffer: bytes) -> str:
         """
         Returns a signed message from a raw buffer.
         Args:
             buffer: Buffer to sign
         Returns:
-            bytes: Signed buffer
+            str: Signature in preferred format
         """
-        
+        raise NotImplementedError
 
     @abstractmethod
     def get_address(self) -> str:
diff --git a/src/aleph/sdk/chains/cosmos.py b/src/aleph/sdk/chains/cosmos.py
index c1e29d5b..7fadd133 100644
--- a/src/aleph/sdk/chains/cosmos.py
+++ b/src/aleph/sdk/chains/cosmos.py
@@ -51,20 +51,11 @@ def __init__(self, private_key=None, hrp=DEFAULT_HRP):
 
     async def sign_message(self, message):
         message = self._setup_sender(message)
-
         verif = get_verification_string(message)
-
-        privkey = ecdsa.SigningKey.from_string(self.private_key, curve=ecdsa.SECP256k1)
-        signature_compact = privkey.sign_deterministic(
-            verif.encode("utf-8"),
-            hashfunc=hashlib.sha256,
-            sigencode=ecdsa.util.sigencode_string_canonize,
-        )
-        signature_base64_str = base64.b64encode(signature_compact).decode("utf-8")
         base64_pubkey = base64.b64encode(self.get_public_key().encode()).decode("utf-8")
 
         sig = {
-            "signature": signature_base64_str,
+            "signature": self.sign_raw(verif.encode("utf-8")),
             "pub_key": {"type": "tendermint/PubKeySecp256k1", "value": base64_pubkey},
             "account_number": str(0),
             "sequence": str(0),
@@ -72,6 +63,15 @@ async def sign_message(self, message):
         message["signature"] = json.dumps(sig)
         return message
 
+    async def sign_raw(self, buffer: bytes) -> str:
+        privkey = ecdsa.SigningKey.from_string(self.private_key, curve=ecdsa.SECP256k1)
+        signature_compact = privkey.sign_deterministic(
+            buffer,
+            hashfunc=hashlib.sha256,
+            sigencode=ecdsa.util.sigencode_string_canonize,
+        )
+        return base64.b64encode(signature_compact).decode("utf-8")
+
     def get_address(self) -> str:
         return privkey_to_address(self.private_key)
 
diff --git a/src/aleph/sdk/chains/ethereum.py b/src/aleph/sdk/chains/ethereum.py
index a6e516f6..40ee2003 100644
--- a/src/aleph/sdk/chains/ethereum.py
+++ b/src/aleph/sdk/chains/ethereum.py
@@ -1,5 +1,5 @@
 from pathlib import Path
-from typing import Dict, Optional, Union
+from typing import Optional, Union
 
 from eth_account import Account
 from eth_account.messages import encode_defunct
@@ -11,7 +11,6 @@
     BaseAccount,
     get_fallback_private_key,
     get_public_key,
-    get_verification_buffer,
 )
 
 
@@ -23,12 +22,12 @@ class ETHAccount(BaseAccount):
     def __init__(self, private_key: bytes):
         self.private_key = private_key
         self._account = Account.from_key(self.private_key)
-    
-    async def sign_raw(self, buffer: bytes) -> bytes:
+
+    async def sign_raw(self, buffer: bytes) -> str:
         """Sign a raw buffer."""
         msghash = encode_defunct(text=buffer.decode("utf-8"))
         sig = self._account.sign_message(msghash)
-        return sig["signature"]
+        return sig["signature"].hex()
 
     def get_address(self) -> str:
         return self._account.address
diff --git a/src/aleph/sdk/chains/nuls1.py b/src/aleph/sdk/chains/nuls1.py
index c5629fb7..12ffaa37 100644
--- a/src/aleph/sdk/chains/nuls1.py
+++ b/src/aleph/sdk/chains/nuls1.py
@@ -315,6 +315,10 @@ async def sign_message(self, message):
         message["signature"] = sig.serialize().hex()
         return message
 
+    async def sign_raw(self, buffer: bytes) -> str:
+        sig = NulsSignature.sign_data(self.private_key, buffer)
+        return sig.serialize().hex()
+
     def get_address(self):
         return address_from_hash(
             public_key_to_hash(self.get_public_key(), chain_id=self.chain_id)
diff --git a/src/aleph/sdk/chains/nuls2.py b/src/aleph/sdk/chains/nuls2.py
index ec1a367d..7618a02a 100644
--- a/src/aleph/sdk/chains/nuls2.py
+++ b/src/aleph/sdk/chains/nuls2.py
@@ -12,7 +12,6 @@
     BaseAccount,
     get_fallback_private_key,
     get_public_key,
-    get_verification_buffer,
 )
 
 
@@ -37,16 +36,9 @@ def __init__(self, private_key=None, chain_id=1, prefix=None):
         else:
             self.prefix = prefix
 
-    async def sign_message(self, message):
-        # sig = NulsSignature.sign_message(self.private_key,
-        #                                  get_verification_buffer(message))
-        message = self._setup_sender(message)
-
-        sig = sign_recoverable_message(
-            self.private_key, get_verification_buffer(message)
-        )
-        message["signature"] = base64.b64encode(sig).decode()
-        return message
+    async def sign_raw(self, buffer: bytes) -> str:
+        sig = sign_recoverable_message(self.private_key, buffer)
+        return base64.b64encode(sig).decode()
 
     def get_address(self):
         return address_from_hash(
diff --git a/src/aleph/sdk/chains/remote.py b/src/aleph/sdk/chains/remote.py
index 8b27e615..250fcc62 100644
--- a/src/aleph/sdk/chains/remote.py
+++ b/src/aleph/sdk/chains/remote.py
@@ -77,6 +77,9 @@ async def sign_message(self, message: Dict) -> Dict:
             response.raise_for_status()
             return await response.json()
 
+    async def sign_raw(self, buffer: bytes) -> str:
+        raise NotImplementedError()
+
     def get_address(self) -> str:
         return self._address
 
diff --git a/src/aleph/sdk/chains/sol.py b/src/aleph/sdk/chains/sol.py
index cc5a2cfa..96e4b2bf 100644
--- a/src/aleph/sdk/chains/sol.py
+++ b/src/aleph/sdk/chains/sol.py
@@ -32,15 +32,15 @@ async def sign_message(self, message: Dict) -> Dict:
         verif = get_verification_buffer(message)
         sig = {
             "publicKey": self.get_address(),
-            "signature": encode(self.sign_raw(verif)),
+            "signature": self.sign_raw(verif),
         }
         message["signature"] = json.dumps(sig)
         return message
 
-    async def sign_raw(self, buffer: bytes) -> bytes:
+    async def sign_raw(self, buffer: bytes) -> str:
         """Sign a raw buffer."""
         sig = self._signing_key.sign(buffer)
-        return sig.signature
+        return encode(sig.signature)
 
     def get_address(self) -> str:
         return encode(self._signing_key.verify_key)
diff --git a/src/aleph/sdk/chains/substrate.py b/src/aleph/sdk/chains/substrate.py
index cc73a8b0..0f49c70e 100644
--- a/src/aleph/sdk/chains/substrate.py
+++ b/src/aleph/sdk/chains/substrate.py
@@ -25,6 +25,10 @@ async def sign_message(self, message):
         message["signature"] = json.dumps(sig)
         return message
 
+    async def sign_raw(self, buffer: bytes) -> str:
+        sig = self._account.sign(buffer)
+        return sig.hex()
+
     def get_address(self):
         return self._account.ss58_address
 
diff --git a/src/aleph/sdk/chains/tezos.py b/src/aleph/sdk/chains/tezos.py
index af870c35..d31e2f8c 100644
--- a/src/aleph/sdk/chains/tezos.py
+++ b/src/aleph/sdk/chains/tezos.py
@@ -27,12 +27,15 @@ async def sign_message(self, message: Dict) -> Dict:
         verif = get_verification_buffer(message)
         sig = {
             "publicKey": self.get_public_key(),
-            "signature": self._account.sign(verif),
+            "signature": self.sign_raw(verif),
         }
 
         message["signature"] = json.dumps(sig)
         return message
 
+    async def sign_raw(self, buffer: bytes) -> str:
+        return self._account.sign(buffer)
+
     def get_address(self) -> str:
         return self._account.public_key_hash()
 
diff --git a/src/aleph/sdk/client.py b/src/aleph/sdk/client.py
index 430ace1f..d48fded9 100644
--- a/src/aleph/sdk/client.py
+++ b/src/aleph/sdk/client.py
@@ -6,6 +6,7 @@
 import threading
 import time
 from datetime import datetime
+from io import BytesIO
 from pathlib import Path
 from typing import (
     Any,
@@ -23,7 +24,6 @@
     TypeVar,
     Union,
 )
-from io import BytesIO
 
 import aiohttp
 from aleph_message.models import (
@@ -45,17 +45,18 @@
 )
 from aleph_message.models.execution.base import Encoding
 from aleph_message.status import MessageStatus
-from pydantic import ValidationError, BaseModel
+from pydantic import ValidationError
 
 from aleph.sdk.types import Account, GenericMessage, StorageEnum
-from aleph.sdk.utils import copy_async_readable_to_buffer, Writable, AsyncReadable
+from aleph.sdk.utils import Writable, copy_async_readable_to_buffer
+
 from .conf import settings
 from .exceptions import (
     BroadcastError,
+    FileTooLarge,
     InvalidMessageError,
     MessageNotFoundError,
     MultipleMessagesError,
-    FileTooLarge,
 )
 from .models import MessagesResponse
 from .utils import check_unix_socket_valid, get_message_type_value
@@ -237,12 +238,24 @@ def download_file_ipfs(self, file_hash: str) -> bytes:
             self.async_session.download_file_ipfs,
             file_hash=file_hash,
         )
-    def download_file_to_buffer(self, file_hash: str, output_buffer: Writable[bytes]) -> bytes:
-        return self._wrap(self.async_session.download_file_to_buffer, file_hash=file_hash, output_buffer=output_buffer)
 
-    def download_file_ipfs_to_buffer(self, file_hash: str, output_buffer: Writable[bytes]) -> bytes:
-        return self._wrap(self.async_session.download_file_ipfs_to_buffer, file_hash=file_hash, output_buffer=output_buffer)
+    def download_file_to_buffer(
+        self, file_hash: str, output_buffer: Writable[bytes]
+    ) -> bytes:
+        return self._wrap(
+            self.async_session.download_file_to_buffer,
+            file_hash=file_hash,
+            output_buffer=output_buffer,
+        )
 
+    def download_file_ipfs_to_buffer(
+        self, file_hash: str, output_buffer: Writable[bytes]
+    ) -> bytes:
+        return self._wrap(
+            self.async_session.download_file_ipfs_to_buffer,
+            file_hash=file_hash,
+            output_buffer=output_buffer,
+        )
 
     def watch_messages(
         self,
diff --git a/src/aleph/sdk/utils.py b/src/aleph/sdk/utils.py
index 91c45c26..be56cc2c 100644
--- a/src/aleph/sdk/utils.py
+++ b/src/aleph/sdk/utils.py
@@ -4,7 +4,7 @@
 from enum import Enum
 from pathlib import Path
 from shutil import make_archive
-from typing import Tuple, Type, Union
+from typing import Protocol, Tuple, Type, TypeVar, Union
 from zipfile import BadZipFile, ZipFile
 
 from aleph_message.models import MessageType
@@ -13,13 +13,6 @@
 from aleph.sdk.conf import settings
 from aleph.sdk.types import GenericMessage
 
-from typing import (
-    Tuple,
-    Type,
-    TypeVar,
-    Protocol,
-)
-
 logger = logging.getLogger(__name__)
 
 try:
@@ -54,7 +47,7 @@ def create_archive(path: Path) -> Tuple[Path, Encoding]:
             return archive_path, Encoding.zip
     elif os.path.isfile(path):
         if path.suffix == ".squashfs" or (
-                magic and magic.from_file(path).startswith("Squashfs filesystem")
+            magic and magic.from_file(path).startswith("Squashfs filesystem")
         ):
             return path, Encoding.squashfs
         else:
@@ -101,7 +94,7 @@ def write(self, buffer: U) -> int:
 
 
 async def copy_async_readable_to_buffer(
-        readable: AsyncReadable[T], buffer: Writable[T], chunk_size: int
+    readable: AsyncReadable[T], buffer: Writable[T], chunk_size: int
 ):
     while True:
         chunk = await readable.read(chunk_size)
diff --git a/tests/unit/test_download.py b/tests/unit/test_download.py
index 219ccde5..df14cce9 100644
--- a/tests/unit/test_download.py
+++ b/tests/unit/test_download.py
@@ -1,4 +1,5 @@
 import pytest
+
 from aleph.sdk import AlephClient
 from aleph.sdk.conf import settings as sdk_settings