Add header fields (#16)

feat: add header fields

internal/block/header.go

@@ -1,4 +1,29 @@
 package block
 
+import (
+	"github.com/eigerco/strawberry/internal/crypto"
+	"github.com/eigerco/strawberry/internal/time"
+)
+
+const NumberOfValidators uint16 = 1023
+
+// Header as defined in the section 5 in the paper
 type Header struct {
+	ParentHash           crypto.Hash                     // Hp
+	PriorStateRoot       crypto.Hash                     // Hr
+	ExtrinsicHash        crypto.Hash                     // Hx
+	TimeSlotIndex        time.Timeslot                   // Ht
+	EpochMarker          *EpochMarker                    // He
+	WinningTicketsMarker [time.TimeslotsPerEpoch]*Ticket // Hw
+	JudgementsMarkers    []crypto.Hash                   // Hj
+	PublicKeyIndex       uint16                          // Hk
+	VRFSignature         crypto.BandersnatchSignature    // Hv
+	BlockSealSignature   crypto.BandersnatchSignature    // Hs
+}
+
+// EpochMarker consists of epoch randomness and a sequence of
+// Bandersnatch keys defining the Bandersnatch validator keys (kb) beginning in the next epoch.
+type EpochMarker struct {
+	Keys    [NumberOfValidators]crypto.BandersnatchPublicKey
+	Entropy crypto.Hash
 }

internal/crypto/bandersnatch.go

@@ -0,0 +1,4 @@
+package crypto
+
+type BandersnatchPublicKey [BandersnatchSize]byte
+type BandersnatchSignature [96]byte