diff --git a/pkg/beacon/entry/entry_test.go b/pkg/beacon/entry/entry_test.go
new file mode 100644
index 0000000000..4be516bbb5
--- /dev/null
+++ b/pkg/beacon/entry/entry_test.go
@@ -0,0 +1,74 @@
+package entry
+
+import (
+	"math/big"
+	"testing"
+
+	bn256 "github.com/ethereum/go-ethereum/crypto/bn256/cloudflare"
+
+	"github.com/keep-network/keep-core/pkg/bls"
+	"github.com/keep-network/keep-core/pkg/protocol/group"
+)
+
+// extractAndValidateShare is the gatekeeper that decides whether a signature
+// share received from another group member is trustworthy. A member that
+// accepted a bad share would contribute to a corrupt relay entry, so each
+// rejection path matters as much as the accept path.
+func TestExtractAndValidateShare(t *testing.T) {
+	senderID := group.MemberIndex(2)
+	secretKey := big.NewInt(1234567)
+
+	// previousEntry is the G1 point being signed; the share is the point
+	// signed with the sender's secret key and the public key share is the
+	// matching G2 public key.
+	previousEntry := new(bn256.G1).ScalarBaseMult(big.NewInt(7))
+	validShare := bls.SignG1(secretKey, previousEntry)
+	publicKeyShare := new(bn256.G2).ScalarBaseMult(secretKey)
+
+	t.Run("valid share", func(t *testing.T) {
+		message := NewSignatureShareMessage(senderID, validShare.Marshal(), "s")
+		shares := map[group.MemberIndex]*bn256.G2{senderID: publicKeyShare}
+
+		share, err := extractAndValidateShare(message, shares, previousEntry)
+		if err != nil {
+			t.Fatalf("unexpected error: [%v]", err)
+		}
+		if share == nil {
+			t.Fatal("expected a non-nil share")
+		}
+		// The returned share must be the one carried by the message.
+		if !bls.VerifyG1(publicKeyShare, previousEntry, share) {
+			t.Error("returned share does not verify against the public key share")
+		}
+	})
+
+	t.Run("unparseable share bytes", func(t *testing.T) {
+		message := NewSignatureShareMessage(senderID, []byte{0x01, 0x02}, "s")
+		shares := map[group.MemberIndex]*bn256.G2{senderID: publicKeyShare}
+
+		if _, err := extractAndValidateShare(message, shares, previousEntry); err == nil {
+			t.Error("expected an error for share bytes that are not a valid G1 point")
+		}
+	})
+
+	t.Run("no public key share for sender", func(t *testing.T) {
+		message := NewSignatureShareMessage(senderID, validShare.Marshal(), "s")
+		shares := map[group.MemberIndex]*bn256.G2{} // sender absent
+
+		if _, err := extractAndValidateShare(message, shares, previousEntry); err == nil {
+			t.Error("expected an error when the sender has no known public key share")
+		}
+	})
+
+	t.Run("share does not verify", func(t *testing.T) {
+		// A share signed with a different secret key than the public key share
+		// advertises must be rejected.
+		wrongShare := bls.SignG1(big.NewInt(7654321), previousEntry)
+		message := NewSignatureShareMessage(senderID, wrongShare.Marshal(), "s")
+		shares := map[group.MemberIndex]*bn256.G2{senderID: publicKeyShare}
+
+		if _, err := extractAndValidateShare(message, shares, previousEntry); err == nil {
+			t.Error("expected an error for a share that does not verify")
+		}
+	})
+}
diff --git a/pkg/beacon/entry/message_test.go b/pkg/beacon/entry/message_test.go
new file mode 100644
index 0000000000..0e905e0a2b
--- /dev/null
+++ b/pkg/beacon/entry/message_test.go
@@ -0,0 +1,67 @@
+package entry
+
+import (
+	"testing"
+
+	"google.golang.org/protobuf/proto"
+
+	"github.com/keep-network/keep-core/internal/testutils"
+	"github.com/keep-network/keep-core/pkg/beacon/entry/gen/pb"
+	"github.com/keep-network/keep-core/pkg/protocol/group"
+)
+
+func TestNewSignatureShareMessage(t *testing.T) {
+	senderID := group.MemberIndex(7)
+	shareBytes := []byte{0x01, 0x02, 0x03}
+	sessionID := "session-1"
+
+	message := NewSignatureShareMessage(senderID, shareBytes, sessionID)
+
+	if message.SenderID() != senderID {
+		t.Errorf(
+			"unexpected sender ID\nexpected: [%v]\nactual:   [%v]",
+			senderID,
+			message.SenderID(),
+		)
+	}
+	testutils.AssertBytesEqual(t, shareBytes, message.shareBytes)
+	if message.sessionID != sessionID {
+		t.Errorf(
+			"unexpected session ID\nexpected: [%v]\nactual:   [%v]",
+			sessionID,
+			message.sessionID,
+		)
+	}
+}
+
+// The Type string is the wire identifier used to route this message on the
+// broadcast channel. Changing it silently would break network compatibility
+// with other clients, so it must stay stable.
+func TestSignatureShareMessageType(t *testing.T) {
+	message := &SignatureShareMessage{}
+
+	if got := message.Type(); got != "relay/signature/share" {
+		t.Errorf(
+			"unexpected message type\nexpected: [relay/signature/share]\nactual:   [%v]",
+			got,
+		)
+	}
+}
+
+// MemberIndex is a uint8 in the protocol but uint32 on the wire; Unmarshal must
+// reject values that would overflow the uint8 rather than silently truncating
+// them into a valid-looking but wrong member index.
+func TestUnmarshalRejectsOverflowingMemberIndex(t *testing.T) {
+	overflowing, err := proto.Marshal(&pb.SignatureShare{
+		SenderID:  256, // maxMemberIndex is 255
+		Share:     []byte{0x01},
+		SessionID: "session-1",
+	})
+	if err != nil {
+		t.Fatalf("failed to marshal test fixture: [%v]", err)
+	}
+
+	if err := (&SignatureShareMessage{}).Unmarshal(overflowing); err == nil {
+		t.Fatal("expected an error for a member index exceeding the uint8 range")
+	}
+}