diff --git a/blockchain/blockchain.go b/blockchain/blockchain.go
new file mode 100644
index 0000000..9bc97d1
--- /dev/null
+++ b/blockchain/blockchain.go
@@ -0,0 +1,44 @@
+package blockchain
+
+import (
+	"crypto/sha256"
+	"encoding/binary"
+)
+
+type BlockHeader struct {
+	blockNumber uint32
+	lastBlock   Hash
+	miner       Wallet
+}
+
+func (bh *BlockHeader) Marshal() []byte {
+	buf := []byte{}
+	binary.LittleEndian.PutUint32(buf, bh.blockNumber)
+	buf = append(buf, bh.lastBlock...)
+	buf = append(buf, bh.miner.Marshal()...)
+	return buf
+}
+
+type Block struct {
+	BlockHeader
+	transactions []Transaction
+}
+
+func (b *Block) Marshal() []byte {
+	buf := b.BlockHeader.Marshal()
+	for _, t := range b.transactions {
+		buf = append(buf, t.Marshal()...)
+	}
+	return buf
+}
+
+func (b *Block) Hash() []byte {
+	sum := sha256.Sum256(b.Marshal())
+	return sum[:]
+}
+
+type BlockChain []Block
+
+func (bc BlockChain) Verify(b *Block) {
+
+}
diff --git a/blockchain/transaction.go b/blockchain/transaction.go
new file mode 100644
index 0000000..847d250
--- /dev/null
+++ b/blockchain/transaction.go
@@ -0,0 +1,50 @@
+package blockchain
+
+import (
+	"encoding/binary"
+)
+
+// TxHashPointer is a reference to a transaction on the blockchain.
+type TxHashPointer struct {
+	blockNumber uint32
+	hash        []byte
+}
+
+func (thp TxHashPointer) Marshal() []byte {
+	buf := []byte{}
+	binary.LittleEndian.PutUint32(buf, thp.blockNumber)
+	return append(buf, thp.hash...)
+}
+
+// TxBody contains all relevant information about a transaction.
+type TxBody struct {
+	sender  Wallet
+	inputs  []TxHashPointer
+	outputs []TxHashPointer
+}
+
+func (tb *TxBody) Marshal() []byte {
+	buf := tb.sender.Marshal()
+	for _, input := range tb.inputs {
+		buf = append(buf, input.Marshal()...)
+	}
+	for _, output := range tb.outputs {
+		buf = append(buf, output.Marshal()...)
+	}
+	return buf
+}
+
+// Transaction contains a TxBody and a signature verifying it.
+type Transaction struct {
+	TxBody
+	hash Hash
+	sig  Signature
+}
+
+func (t *Transaction) Marshal() []byte {
+	buf := t.TxBody.Marshal()
+	buf = append(buf, t.hash...)
+	buf = append(buf, t.sig.X.Bytes()...)
+	buf = append(buf, t.sig.Y.Bytes()...)
+	return buf
+}
diff --git a/blockchain/wallet.go b/blockchain/wallet.go
new file mode 100644
index 0000000..0f99636
--- /dev/null
+++ b/blockchain/wallet.go
@@ -0,0 +1,50 @@
+package blockchain
+
+import (
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rand"
+	"fmt"
+	"math/big"
+)
+
+var curve = elliptic.P256()
+
+// Wallet represents a Cumulus wallet address in the blockchain.
+type Wallet ecdsa.PublicKey
+
+// Hash represents a hash of a transaction.
+type Hash []byte
+
+// Signature represents a signature of a transaction.
+type Signature struct {
+	X big.Int
+	Y big.Int
+}
+
+// New creates a new Wallet backed by a ECC key pair. Uses system entropy.
+func NewWallet() (*Wallet, error) {
+	k, err := ecdsa.GenerateKey(curve, rand.Reader)
+	if err != nil {
+		return nil, err
+	}
+	pk := Wallet(k.PublicKey)
+	return &pk, nil
+}
+
+func (w *Wallet) String() string {
+	return fmt.Sprintf("%x-%x", w.X, w.Y)
+}
+
+func (w *Wallet) Marshal() []byte {
+	return elliptic.Marshal(curve, w.X, w.Y)
+}
+
+func (w *Wallet) Equals(other *Wallet) bool {
+	return w.X.Cmp(other.X) == 0 && w.Y.Cmp(other.Y) == 0
+}
+
+func Unmarshal(wallet []byte) *Wallet {
+	x, y := elliptic.Unmarshal(curve, wallet)
+	return &Wallet{curve, x, y}
+}
diff --git a/blockchain/wallet_test.go b/blockchain/wallet_test.go
new file mode 100644
index 0000000..76f922d
--- /dev/null
+++ b/blockchain/wallet_test.go
@@ -0,0 +1,20 @@
+package blockchain
+
+import (
+	"fmt"
+	"testing"
+)
+
+func TestUnmarshal(t *testing.T) {
+	w, err := NewWallet()
+	if err != nil {
+		t.Fail()
+	}
+
+	unmarshalled := Unmarshal(w.Marshal())
+	fmt.Println("w", w.X, w.Y)
+	fmt.Println("u", unmarshalled.X, unmarshalled.Y)
+	if !w.Equals(unmarshalled) {
+		t.Fatal("Unmarshal produced a different wallet")
+	}
+}