feat: add block id, transaction id, and certificate hash

- Block.id: blake2b-256 of header + cert_hash + merkle_root + tx_count
- Transaction.id(): blake2b-256 of sign_bytes
- Certificate.hash(): blake2b-256 of encoded certificate
- Simple merkle tree implementation for TX root
- Test updated with expected block id

Author: b00f

pactus/block/block.py

@@ -1,5 +1,8 @@
 from __future__ import annotations
 
+import hashlib
+import struct
+
 from pactus.encoding import encoding
 from pactus.transaction import Transaction
 
@@ -38,3 +41,53 @@ def decode(cls, data: bytes) -> Block:
             transactions.append(tx)
 
         return cls(header, prev_cert, transactions)
+
+    @property
+    def id(self) -> bytes:
+        """Return the block ID (blake2b-256 of header + cert_hash + tx_root + tx_count)."""
+        buf = self._header_bytes()
+        if self.prev_cert is not None:
+            buf += self.prev_cert.hash()
+        buf += self._txs_root()
+        buf += struct.pack("<i", len(self.transactions))
+        return hashlib.blake2b(buf, digest_size=32).digest()
+
+    def _header_bytes(self) -> bytes:
+        h = self.header
+        buf = encoding.append_uint8(b"", h.version)
+        buf = encoding.append_uint32(buf, h.unix_time)
+        buf = h.prev_block_hash.encode(buf)
+        buf = h.state_root.encode(buf)
+        buf = encoding.append_fixed_bytes(buf, h.sortition_seed)
+        return h.proposer_address.encode(buf)
+
+    def _txs_root(self) -> bytes:
+        return Block._merkle_root([tx.id() for tx in self.transactions])
+
+    @staticmethod
+    def _merkle_root(hashes: list) -> bytes:
+        if not hashes:
+            return bytes(32)
+
+        # Build simple merkle tree
+        n = 1
+        while n < len(hashes):
+            n <<= 1
+
+        tree = [None] * (n * 2 - 1)
+        for i, h in enumerate(hashes):
+            tree[i] = h
+
+        offset = n
+        for i in range(0, len(tree) - 1, 2):
+            left = tree[i]
+            right = tree[i + 1]
+            if left is None:
+                tree[offset] = None
+            elif right is None:
+                tree[offset] = hashlib.blake2b(left + left, digest_size=32).digest()
+            else:
+                tree[offset] = hashlib.blake2b(left + right, digest_size=32).digest()
+            offset += 1
+
+        return tree[-1] or bytes(32)

pactus/block/certificate.py

@@ -1,3 +1,5 @@
+import hashlib
+
 from pactus.crypto.bls.signature import Signature
 from pactus.encoding import encoding
 from pactus.types.height import Height
@@ -44,3 +46,16 @@ def decode(cls, buf: bytes) -> tuple:
 
         cert = cls(height, round_, committers, absentees, signature)
         return cert, buf
+
+    def hash(self) -> bytes:
+        """Return the certificate hash (blake2b-256 of encoded bytes)."""
+        buf = self.height.encode(b"")
+        buf = self.round.encode(buf)
+        buf = encoding.append_var_int(buf, len(self.committers))
+        for n in self.committers:
+            buf = encoding.append_var_int(buf, n)
+        buf = encoding.append_var_int(buf, len(self.absentees))
+        for n in self.absentees:
+            buf = encoding.append_var_int(buf, n)
+        buf = self.signature.encode(buf)
+        return hashlib.blake2b(buf, digest_size=32).digest()

pactus/transaction/transaction.py

@@ -1,5 +1,7 @@
 from __future__ import annotations
 
+import hashlib
+
 from pactus.crypto.address import Address, AddressType
 from pactus.crypto.bls.public_key import PublicKey as BLSPublicKey
 from pactus.crypto.bls.signature import Signature as BLSSignature
@@ -182,6 +184,10 @@ def sign_bytes(self) -> bytes:
         buf = self._get_unsigned_bytes(b"")
         return buf[1:]
 
+    def id(self) -> bytes:
+        """Return the transaction ID (blake2b-256 of sign bytes)."""
+        return hashlib.blake2b(self.sign_bytes(), digest_size=32).digest()
+
     def sign(self, private_key: PrivateKey) -> bytes:
         """Sign the transaction and return signed bytes."""
         buf = self._get_unsigned_bytes(b"")

tests/test_block.py

@@ -7,6 +7,8 @@
 
 class TestBlockDecode(unittest.TestCase):
     def test_decode_block_from_raw(self):
+        # Block number of 888
+        #  https://pactusscan.com/block/888
         raw_hex = (
             "019094b165"
             "84fdb8aac442735c6d4d4457e2236cd6ca86cb0b898ab37a03be1723b8faac55"
@@ -64,6 +66,12 @@ def test_decode_block_from_raw(self):
             "43d6f72983bf25ce856946df1360710f",
         )
 
+        # --- Block ID ---
+        self.assertEqual(
+            block.id.hex(),
+            "3fad130499227f7a83d4e65873b0f880db275a6c4d1b9dd65005c1f1667ec98f",
+        )
+
         # --- Transactions ---
         self.assertEqual(len(block.transactions), 1)