diff --git a/README.md b/README.md
index 28f4791..783e2f5 100644
--- a/README.md
+++ b/README.md
@@ -15,3 +15,9 @@ To test a specific module
 ```bash
 python -m unittest -v cryptarchia.test_leader
 ```
+
+Or all test modules in a directory
+
+```bash
+python -m unittest -v cryptarchia/test_*
+```
diff --git a/cryptarchia/cryptarchia.py b/cryptarchia/cryptarchia.py
index 8ad59ca..64defba 100644
--- a/cryptarchia/cryptarchia.py
+++ b/cryptarchia/cryptarchia.py
@@ -87,13 +87,6 @@ class MockLeaderProof:
         # TODO: verification not implemented
         return True
 
-    def _block_id_update(self, hasher):
-        # TODO: this is used to contribute to the block id, to ensure the id is dependent
-        # on the leader proof, but the details here are not specified yet, we're waiting on
-        # CL specification before we nail this down
-        hasher.update(self.commitment)
-        hasher.update(self.nullifier)
-
 
 @dataclass
 class BlockHeader:
@@ -109,24 +102,30 @@ class BlockHeader:
     #
     # The following code is to be considered as a reference implementation, mostly to be used for testing.
     def id(self) -> Id:
-        # version byte
         h = blake2b(digest_size=32)
+
+        # version byte
         h.update(b"\x01")
-        # header type
-        h.update(b"\x00")
+
         # content size
         h.update(int.to_bytes(self.content_size, length=4, byteorder="big"))
+
         # content id
         assert len(self.content_id) == 32
         h.update(self.content_id)
+
         # slot
         h.update(int.to_bytes(self.slot.absolute_slot, length=8, byteorder="big"))
+
         # parent
         assert len(self.parent) == 32
         h.update(self.parent)
 
-        # TODO: Leader proof component of block id is mocked here until CL is understood
-        self.leader_proof._block_id_update(h)
+        # leader proof
+        assert len(self.leader_proof.commitment) == 32
+        h.update(self.leader_proof.commitment)
+        assert len(self.leader_proof.nullifier) == 32
+        h.update(self.leader_proof.nullifier)
 
         return h.digest()
 
diff --git a/cryptarchia/messages.abnf b/cryptarchia/messages.abnf
index ef3e7c5..fefd6a6 100644
--- a/cryptarchia/messages.abnf
+++ b/cryptarchia/messages.abnf
@@ -2,15 +2,14 @@
 ; ------------ BLOCK ----------------------
 BLOCK            = HEADER CONTENT
 ; ------------ HEADER ---------------------
-VERSION          = %x01
-HEADER           = VERSION HEADER-UNSIGNED LEADER-PROOF
-HEADER-UNSIGNED  = %x00 HEADER-COMMON
-HEADER-COMMON    = CONTENT-SIZE CONTENT-ID BLOCK-DATE PARENT-ID
-CONTENT-SIZE     = U32
-BLOCK-DATE       = BLOCK-SLOT
-BLOCK-SLOT       = U64
-PARENT-ID        = HEADER-ID
-LEADER-PROOF     = <NOT SPECIFIED YET>
+VERSION           = %x01
+HEADER            = VERSION HEADER-FIELDS MOCK-LEADER-PROOF
+HEADER-FIELDS     = CONTENT-SIZE CONTENT-ID BLOCK-DATE PARENT-ID
+CONTENT-SIZE      = U32
+BLOCK-DATE        = BLOCK-SLOT
+BLOCK-SLOT        = U64
+PARENT-ID         = HEADER-ID
+MOCK-LEADER-PROOF = COMMITMENT NULLIFIER
 
 ; ------------ CONTENT --------------------
 CONTENT          = *OCTET
@@ -20,3 +19,5 @@ U32              = 4OCTET  ; unsigned integer 32 bit (BE)
 U64              = 8OCTET  ; unsigned integer 32 bit (BE)
 HEADER-ID        = 32OCTET
 CONTENT-ID       = 32OCTET
+COMMITMENT       = 32OCTET
+NULLIFIER        = 32OCTET