feat: add verification module

src/pyzantium/verify.py

@@ -0,0 +1,80 @@
+from abc import ABC, abstractmethod
+from typing import Any
+
+from cryptography.hazmat.primitives.asymmetric import ec, utils
+from cryptography.hazmat.primitives import hashes
+from cryptography.exceptions import InvalidSignature
+
+
+class Verifier(ABC):
+    """
+    Abstract base class for validating data.
+
+    This class provide an interface for data verifiers to verify data that
+    will append to a block.
+    """
+
+    def __init__(self) -> None:
+        super().__init__()
+
+    @abstractmethod
+    def verify(self, data: bytes) -> bool:
+        """
+        Checks verify (Authority) of data
+
+        :param data: Data that will be added to block
+        :return: True if signature is ok, False otherwise
+        """
+        ...
+
+
+class ECCVerifier(Verifier):
+    """
+    Data verifier using ECC
+
+    This verifier checks validity based on a digital signature produced by an
+    Elliptic curve.
+
+    :param pkey: Elliptic curve public key of author
+    :param hash: Hash algorithm used to generate signature
+    :param signature: Signature of this data
+    """
+
+    def __init__(
+        self, pkey: ec.EllipticCurvePublicKey, hash: hashes.Hash, signature: bytes
+    ) -> None:
+        super().__init__()
+        self._pkey = pkey
+        self._hash = hash
+        self._signature = signature
+
+    def verify(self, data: bytes) -> bool:
+        hasher = hashes.Hash(self._hash)
+
+        # TODO: hash data with chunks
+        hasher.update(data)
+        digest = hasher.finalize()
+
+        dsa = ec.ECDSA(utils.Prehashed(hasher))
+
+        try:
+            self._pkey.verify(self._signature, digest, dsa)
+        except InvalidSignature:
+            return False
+
+        return True
+
+
+class VoidVerifier(Verifier):
+    """
+    This is an empty verifier that will say data is valid allwasy
+
+    This class is not intendet to be used in production. Using this verifier
+    will cause to ignore validity of data.
+    """
+
+    def __init__(self) -> None:
+        super().__init__()
+
+    def verify(self, data: bytes) -> bool:
+        return True