diff --git a/core/interfaces.go b/core/interfaces.go
index 5be4bc5..f242360 100644
--- a/core/interfaces.go
+++ b/core/interfaces.go
@@ -5,13 +5,14 @@ import (
 )
 
 type EntryStore interface {
-	Put(ctx context.Context, id EntryID, canonical []byte) error
-	Get(ctx context.Context, id EntryID) ([]byte, error)
-	Has(ctx context.Context, id EntryID) (bool, error)
+	Store(ctx context.Context, entry Entry) error
+	Load(ctx context.Context, id EntryID) (Entry, error)
+	Exists(ctx context.Context, id EntryID) (bool, error)
+	Delete(ctx context.Context, id EntryID) error
 }
 
 type ReferenceStore interface {
-	GetRef(ctx context.Context, name string) (EntryID, bool, error)
-	SetRef(ctx context.Context, name string, entryID EntryID) (bool, error)
-	RemoveRef(ctx context.Context, name string) error
+	Set(ctx context.Context, name string, entryID EntryID) error
+	Get(ctx context.Context, name string) (EntryID, error)
+	Delete(ctx context.Context, name string) error
 }
diff --git a/core/ledger.go b/core/ledger.go
index 73b26cb..d075869 100644
--- a/core/ledger.go
+++ b/core/ledger.go
@@ -7,8 +7,17 @@ type Ledger struct {
 	referenceStore ReferenceStore
 }
 
-func NewLedger(entryStore EntryStore) (*Ledger, error) {
+func NewLedger(entryStore EntryStore, referenceStore ReferenceStore) (*Ledger, error) {
 	return &Ledger{
-		entryStore: entryStore,
+		entryStore:     entryStore,
+		referenceStore: referenceStore,
 	}, nil
 }
+
+func (l *Ledger) Append()            {}
+func (l *Ledger) AppendToReference() {}
+func (l *Ledger) Get()               {}
+func (l *Ledger) GetFromReference()  {}
+func (l *Ledger) SetHead()           {}
+func (l *Ledger) SetReference()      {}
+func (l *Ledger) RemoveReference()   {}
diff --git a/core/types.go b/core/types.go
index 4d9af37..dbbf319 100644
--- a/core/types.go
+++ b/core/types.go
@@ -1,7 +1,10 @@
 package core
 
 import (
+	"encoding/binary"
 	"time"
+
+	"lukechampine.com/blake3"
 )
 
 type EntryID [32]byte
@@ -9,8 +12,28 @@ type EntryID [32]byte
 type Entry struct {
 	EntryID EntryID
 
-	Previous []EntryID
+	Previous EntryID
 
 	Timestamp time.Time
 	Payload   []byte
 }
+
+func ComputeEntryID(prev EntryID, ts time.Time, payload []byte) EntryID {
+	h := blake3.New(32, nil)
+
+	h.Write(prev[:])
+
+	var i64 [8]byte
+	binary.LittleEndian.PutUint64(i64[:], uint64(ts.UTC().UnixNano()))
+	h.Write(i64[:])
+
+	var u32 [4]byte
+	binary.LittleEndian.PutUint32(u32[:], uint32(len(payload)))
+	h.Write(u32[:])
+
+	h.Write(payload)
+
+	var id EntryID
+	copy(id[:], h.Sum(nil))
+	return id
+}