diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..2c53fa7
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+tmp.go
diff --git a/id.go b/id.go
index 09d14f7..d7aaf2c 100644
--- a/id.go
+++ b/id.go
@@ -1,6 +1,7 @@
 package main
 
 import (
+	"bytes"
 	"crypto/rand"
 	"encoding/hex"
 )
@@ -32,6 +33,10 @@ func IDFromString(s string) (ID, error) {
 	return id, nil
 }
 
+func (idA ID) Equal(idB ID) bool {
+	return bytes.Equal(idA[:], idB[:])
+}
+
 // Cmp returns true if idA > idB
 func (idA ID) Cmp(idB ID) bool {
 	for i := 0; i < len(idA); i++ {
diff --git a/id_test.go b/id_test.go
index 8993272..e7abfe8 100644
--- a/id_test.go
+++ b/id_test.go
@@ -7,8 +7,12 @@ import (
 )
 
 func TestNewID(t *testing.T) {
-	_, err := NewID()
-	assert.Nil(t, err)
+	// get some IDs
+	// for i := 0; i < 10; i++ {
+	//         id, err := NewID()
+	//         assert.Nil(t, err)
+	//         fmt.Println(id)
+	// }
 
 	idA, err := IDFromString("0fd85ddddf15aeec2d5d8b01b013dbca030a18d7")
 	assert.Nil(t, err)
diff --git a/kademlia.go b/kademlia.go
new file mode 100644
index 0000000..91fe140
--- /dev/null
+++ b/kademlia.go
@@ -0,0 +1,99 @@
+package main
+
+import (
+	"math/bits"
+	"strconv"
+)
+
+const (
+	alpha       = 3  // 'alpha', max parallalel calls
+	B           = 20 // 'B', 160 bits, ID length
+	KBucketSize = 20 // 'K', bucket size
+)
+
+type ListedNode struct {
+	ID   ID
+	Addr string
+}
+
+type Node struct {
+	ID       ID
+	KBuckets [B * 8][]ListedNode
+}
+
+func (n Node) String() string {
+	r := "Node ID: " + n.ID.String() + ", KBuckets:\n"
+	for i, kb := range n.KBuckets {
+		if len(kb) > 0 {
+			r += "	KBucket " + strconv.Itoa(i) + "\n"
+			for _, e := range kb {
+				r += "		" + e.ID.String() + "\n"
+			}
+		}
+	}
+	return r
+}
+
+func NewNode() (Node, error) {
+	// TODO if node already has id, import it
+	id, err := NewID()
+	if err != nil {
+		return Node{}, err
+	}
+
+	var n Node
+	n.ID = id
+	return n, nil
+}
+
+func LoadNode(idStr string) (Node, error) {
+	id, err := IDFromString("0fd85ddddf15aeec2d5d8b01b013dbca030a18d7")
+	if err != nil {
+		return Node{}, err
+	}
+	var n Node
+	n.ID = id
+	return n, nil
+}
+
+func (n Node) KBucket(o ID) int {
+	d := n.ID.Distance(o)
+	return kBucketByDistance(d[:])
+
+}
+
+func kBucketByDistance(b []byte) int {
+	for i := 0; i < B; i++ {
+		for a := b[i] ^ 0; a != 0; a &= a - 1 {
+			return (B-1-i)*8 + (7 - bits.TrailingZeros8(bits.Reverse8(uint8(a))))
+		}
+	}
+	return (B*8 - 1) - (B*8 - 1)
+}
+
+func (n *Node) Update(o ListedNode) {
+	k := n.KBucket(o.ID)
+	kb := n.KBuckets[k]
+	if len(kb) >= KBucketSize {
+		// TODO ping the kb[0], and if no response, delete it, and add the current o (ID)
+		return
+	}
+	// check that is not already in the list
+	exist, _ := existsInListedNodes(n.KBuckets[k], o)
+	if exist {
+		// update position to the bottom
+		return
+	}
+	// not exists, add it to the kBucket
+	n.KBuckets[k] = append(n.KBuckets[k], o)
+	return
+}
+
+func existsInListedNodes(lns []ListedNode, ln ListedNode) (bool, int) {
+	for i, v := range lns {
+		if v.ID.Equal(ln.ID) {
+			return true, i
+		}
+	}
+	return false, 0
+}
diff --git a/kademlia_test.go b/kademlia_test.go
new file mode 100644
index 0000000..7a2c2a2
--- /dev/null
+++ b/kademlia_test.go
@@ -0,0 +1,97 @@
+package main
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+var debug = true
+
+func TestCountZeros(t *testing.T) {
+	zeroes := []byte{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
+	assert.Equal(t, 0, kBucketByDistance(zeroes))
+
+	b := []byte{0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff}
+	assert.Equal(t, 20, len(b))
+	assert.Equal(t, 159, kBucketByDistance(b))
+	b[19] = 0x00
+	assert.Equal(t, 159, kBucketByDistance(b))
+
+	b[0] = 0x0f
+	assert.Equal(t, 159-4, kBucketByDistance(b))
+
+	b[0] = 0x0c
+	assert.Equal(t, 159-4, kBucketByDistance(b))
+
+	b[0] = 0x00
+	b[1] = 0x00
+	b[2] = 0x0f
+	assert.Equal(t, 159-20, kBucketByDistance(b))
+
+	b[2] = 0x07
+	assert.Equal(t, 159-21, kBucketByDistance(b))
+
+	b[2] = 0x03
+	assert.Equal(t, 159-22, kBucketByDistance(b))
+}
+
+func TestNodeKBucket(t *testing.T) {
+	node, err := LoadNode("0fd85ddddf15aeec2d5d8b01b013dbca030a18d7")
+	assert.Nil(t, err)
+
+	d := node.KBucket(node.ID)
+	assert.Equal(t, 0, d) // same node should have distance 0
+
+	idB, err := IDFromString("c48d8b53dbefb609ed4e94d386dd5b22efcb2c5b")
+	assert.Nil(t, err)
+
+	d = node.KBucket(idB)
+	assert.Equal(t, 159, d)
+}
+
+func TestUpdate(t *testing.T) {
+	nodeA, err := LoadNode("0fd85ddddf15aeec2d5d8b01b013dbca030a18d7")
+	assert.Nil(t, err)
+
+	lnIDs := []string{
+		"c48d8b53dbefb609ed4e94d386dd5b22efcb2c5b",
+		"420bfebd44fc62615253224328f40f29c9b225fa",
+		"6272bb67b1661abfa07d1d32cd9b810e531d42cd",
+		"07db608db033384895e48098a1bbe25266387463",
+		"c19c3285ab9ada4b420050ae1a204640b2bed508",
+		"f8971d5da24517c8cc5a316fb0658de8906c4155",
+		"04122a5f2dec42284147b1847ec1bc41ecd78626",
+		"407a90870d7b482a271446c85fda940ce78a4c7a",
+		"5ebe4539e7a33721a8623f7ebfab62600aa503e7",
+		"fc44a42879ef3a74d6bd8303bc3e4e205a92acf9",
+		"fc44a42879ef3a74d6bd8303bc3e4e205a92acf9",
+		"10c86f96ebaa1685a46a6417e6faa2ef34a68976",
+		"243c81515196a5b0e2d4675e73f0da3eead12793",
+		"0fd85ddddf15aeec2d5d8b01b013dbca030a18d7",
+		"0fd85ddddf15aeec2d5d8b01b013dbca030a18d5",
+		"0fd85ddddf15aeec2d5d8b01b013dbca030a18d0",
+		"0fd85ddddf15aeec2d5d8b01b013dbca030a1800",
+		"0750931c40a52a2facd220a02851f7d34f95e1fa",
+		"ebfba615ac50bcd0f5c2420741d032e885abf576",
+	}
+	for i := 0; i < len(lnIDs); i++ {
+		idI, err := IDFromString(lnIDs[i])
+		assert.Nil(t, err)
+		lnI := ListedNode{
+			ID:   idI,
+			Addr: "",
+		}
+		nodeA.Update(lnI)
+	}
+
+	if debug {
+		fmt.Println(nodeA)
+	}
+
+	assert.Equal(t, len(nodeA.KBuckets[0]), 1)
+	assert.Equal(t, len(nodeA.KBuckets[1]), 1)
+	assert.Equal(t, len(nodeA.KBuckets[158]), 4)
+	assert.Equal(t, len(nodeA.KBuckets[159]), 5)
+}