diff --git a/bigchaindb/crypto/asymmetric.py b/bigchaindb/crypto/asymmetric.py
index f0522ed5..15d5c5f3 100644
--- a/bigchaindb/crypto/asymmetric.py
+++ b/bigchaindb/crypto/asymmetric.py
@@ -23,6 +23,10 @@ class SigningKey(metaclass=ABCMeta):
     def get_verifying_key(self):
         raise NotImplementedError
 
+    @abstractmethod
+    def to_ascii(self, prefix, encoding):
+        raise NotImplementedError
+
     @staticmethod
     @abstractmethod
     def encode(private_value):
@@ -52,6 +56,10 @@ class VerifyingKey(metaclass=ABCMeta):
     def verify(self, data, signature):
         raise NotImplementedError
 
+    @abstractmethod
+    def to_ascii(self, prefix, encoding):
+        raise NotImplementedError
+
     @staticmethod
     @abstractmethod
     def encode(public_value):
diff --git a/bigchaindb/crypto/ecdsa.py b/bigchaindb/crypto/ecdsa.py
index 864b8c86..3139a3ec 100644
--- a/bigchaindb/crypto/ecdsa.py
+++ b/bigchaindb/crypto/ecdsa.py
@@ -34,6 +34,12 @@ class EcdsaSigningKey(SigningKey):
         signature = signer.finalize()
         return binascii.hexlify(signature).decode('utf-8')
 
+    def get_verifying_key(self):
+        raise NotImplementedError
+
+    def to_ascii(self, prefix='', encoding='base58'):
+        raise NotImplementedError
+
     @staticmethod
     def encode(private_value):
         """
@@ -99,6 +105,9 @@ class EcdsaVerifyingKey(VerifyingKey):
 
         return True
 
+    def to_ascii(self, prefix='', encoding='base58'):
+        raise NotImplementedError
+
     @staticmethod
     def encode(public_value_x, public_value_y):
         """