diff --git a/checks.go b/checks.go
new file mode 100644
index 000000000..05647de6c
--- /dev/null
+++ b/checks.go
@@ -0,0 +1,73 @@
+package sealing
+
+import (
+	"context"
+
+	"golang.org/x/xerrors"
+
+	"github.com/filecoin-project/go-address"
+	"github.com/filecoin-project/lotus/chain/actors"
+	"github.com/filecoin-project/lotus/chain/types"
+)
+
+func checkPieces(ctx context.Context, si *SectorInfo, api sealingApi) error {
+	for i, piece := range si.Pieces {
+		deal, err := api.StateMarketStorageDeal(ctx, piece.DealID, nil)
+		if err != nil {
+			return xerrors.Errorf("getting deal %d for piece %d: %w", piece.DealID, i, err)
+		}
+
+		if string(deal.PieceRef) != string(piece.CommP) {
+			return xerrors.Errorf("piece %d of sector %d refers deal %d with wrong CommP: %x != %x", i, si.SectorID, piece.DealID, piece.CommP, deal.PieceRef)
+		}
+
+		if piece.Size != deal.PieceSize {
+			return xerrors.Errorf("piece %d of sector %d refers deal %d with different size: %d != %d", i, si.SectorID, piece.DealID, piece.Size, deal.PieceSize)
+		}
+	}
+
+	return nil
+}
+
+func checkSeal(ctx context.Context, maddr address.Address, si *SectorInfo, api sealingApi) (err error) {
+	ssize, err := api.StateMinerSectorSize(ctx, maddr, nil)
+	if err != nil {
+		return err
+	}
+
+	ccparams, err := actors.SerializeParams(&actors.ComputeDataCommitmentParams{
+		DealIDs:    si.deals(),
+		SectorSize: ssize,
+	})
+	if err != nil {
+		return xerrors.Errorf("computing params for ComputeDataCommitment: %w", err)
+	}
+
+	ccmt := &types.Message{
+		To:       actors.StorageMarketAddress,
+		From:     actors.StorageMarketAddress,
+		Value:    types.NewInt(0),
+		GasPrice: types.NewInt(0),
+		GasLimit: types.NewInt(9999999999),
+		Method:   actors.SMAMethods.ComputeDataCommitment,
+		Params:   ccparams,
+	}
+	r, err := api.StateCall(ctx, ccmt, nil)
+	if err != nil {
+		return xerrors.Errorf("calling ComputeDataCommitment: %w", err)
+	}
+	if r.ExitCode != 0 {
+		return xerrors.Errorf("receipt for ComputeDataCommitment han exit code %d", r.ExitCode)
+	}
+	if string(r.Return) != string(si.CommD) {
+		return xerrors.Errorf("on chain CommD differs from sector: %x != %x", r.Return, si.CommD)
+	}
+
+
+	// TODO: Validate ticket
+	// TODO: Verify commp / commr / proof
+	// TODO: (StateCall PreCommit)
+	return nil
+
+
+}