diff --git a/internal/crypto/constants.go b/internal/crypto/constants.go
new file mode 100644
index 0000000..1aeb486
--- /dev/null
+++ b/internal/crypto/constants.go
@@ -0,0 +1,9 @@
+package crypto
+
+const (
+	HashSize           = 32
+	BandersnatchSize   = 32
+	Ed25519PublicSize  = 32
+	Ed25519PrivateSize = 64
+	BLSSize            = 144
+)
diff --git a/internal/crypto/hash.go b/internal/crypto/hash.go
new file mode 100644
index 0000000..e519686
--- /dev/null
+++ b/internal/crypto/hash.go
@@ -0,0 +1,3 @@
+package crypto
+
+type Hash [HashSize]byte
diff --git a/internal/crypto/keys.go b/internal/crypto/keys.go
new file mode 100644
index 0000000..27cc119
--- /dev/null
+++ b/internal/crypto/keys.go
@@ -0,0 +1,8 @@
+package crypto
+
+import (
+	"crypto/ed25519"
+)
+
+type Ed25519PublicKey ed25519.PublicKey
+type Ed25519PrivateKey ed25519.PrivateKey
diff --git a/internal/state/state.go b/internal/state/state.go
new file mode 100644
index 0000000..a268c97
--- /dev/null
+++ b/internal/state/state.go
@@ -0,0 +1,4 @@
+package state
+
+type State struct {
+}
diff --git a/internal/time/constants.go b/internal/time/constants.go
new file mode 100644
index 0000000..186c1e8
--- /dev/null
+++ b/internal/time/constants.go
@@ -0,0 +1,9 @@
+package time
+
+import "time"
+
+const (
+	TimeslotsPerEpoch = 600
+	TimeslotDuration  = 6 * time.Second
+	EpochDuration     = TimeslotsPerEpoch * TimeslotDuration
+)
diff --git a/internal/time/epoch.go b/internal/time/epoch.go
new file mode 100644
index 0000000..9dc60b0
--- /dev/null
+++ b/internal/time/epoch.go
@@ -0,0 +1,3 @@
+package time
+
+type Epoch uint32
diff --git a/internal/time/timeslot.go b/internal/time/timeslot.go
new file mode 100644
index 0000000..2b3b77e
--- /dev/null
+++ b/internal/time/timeslot.go
@@ -0,0 +1,3 @@
+package time
+
+type Timeslot uint32