diff --git a/src/yggdrasil/tcp.go b/src/yggdrasil/tcp.go
index c5f7927b..e325fcfe 100644
--- a/src/yggdrasil/tcp.go
+++ b/src/yggdrasil/tcp.go
@@ -10,6 +10,10 @@ package yggdrasil
 //  Could be used to DoS (connect, give someone else's keys, spew garbage)
 //  I guess the "peer" part should watch for link packets, disconnect?
 
+// TCP connections start with a metadata exchange.
+//  It involves exchanging version numbers and crypto keys
+//  See version.go for version metadata format
+
 import "net"
 import "time"
 import "errors"
@@ -142,28 +146,39 @@ func (iface *tcpInterface) handler(sock net.Conn, incoming bool) {
 	defer sock.Close()
 	// Get our keys
 	myLinkPub, myLinkPriv := newBoxKeys() // ephemeral link keys
-	keys := []byte{}
-	keys = append(keys, tcp_key[:]...)
-	keys = append(keys, iface.core.boxPub[:]...)
-	keys = append(keys, iface.core.sigPub[:]...)
-	keys = append(keys, myLinkPub[:]...)
-	_, err := sock.Write(keys)
+	meta := version_getBaseMetadata()
+	meta.box = iface.core.boxPub
+	meta.sig = iface.core.sigPub
+	meta.link = *myLinkPub
+	metaBytes := meta.encode()
+	_, err := sock.Write(metaBytes)
 	if err != nil {
 		return
 	}
 	timeout := time.Now().Add(6 * time.Second)
 	sock.SetReadDeadline(timeout)
-	n, err := sock.Read(keys)
+	_, err = sock.Read(metaBytes)
 	if err != nil {
 		return
 	}
-	if n < len(keys) { /*panic("Partial key packet?") ;*/
+	meta = version_metadata{} // Reset to zero value
+	if !meta.decode(metaBytes) || !meta.check() {
+		// Failed to decode and check the metadata
+		// If it's a version mismatch issue, then print an error message
+		base := version_getBaseMetadata()
+		if meta.meta == base.meta {
+			if meta.ver > base.ver {
+				iface.core.log.Println("Failed to connect to node:", sock.RemoteAddr().String(), "version:", meta.ver)
+			} else if meta.ver == base.ver && meta.minorVer > base.minorVer {
+				iface.core.log.Println("Failed to connect to node:", sock.RemoteAddr().String(), "version:", fmt.Sprintf("%d.%d", meta.ver, meta.minorVer))
+			}
+		}
+		// TODO? Block forever to prevent future connection attempts? suppress future messages about the same node?
 		return
 	}
-	info := tcpInfo{} // used as a map key, so don't include ephemeral link eys
-	var theirLinkPub boxPubKey
-	if !tcp_chop_keys(&info.box, &info.sig, &theirLinkPub, &keys) { /*panic("Invalid key packet?") ;*/
-		return
+	info := tcpInfo{ // used as a map key, so don't include ephemeral link key
+		box: meta.box,
+		sig: meta.sig,
 	}
 	// Quit the parent call if this is a connection to ourself
 	equiv := func(k1, k2 []byte) bool {
@@ -210,7 +225,7 @@ func (iface *tcpInterface) handler(sock net.Conn, incoming bool) {
 	}()
 	// Note that multiple connections to the same node are allowed
 	//  E.g. over different interfaces
-	p := iface.core.peers.newPeer(&info.box, &info.sig, getSharedKey(myLinkPriv, &theirLinkPub))
+	p := iface.core.peers.newPeer(&info.box, &info.sig, getSharedKey(myLinkPriv, &meta.link))
 	p.linkOut = make(chan []byte, 1)
 	in := func(bs []byte) {
 		p.handlePacket(bs)
@@ -336,30 +351,8 @@ func (iface *tcpInterface) reader(sock net.Conn, in func([]byte)) {
 ////////////////////////////////////////////////////////////////////////////////
 
 // Magic bytes to check
-var tcp_key = [...]byte{'k', 'e', 'y', 's'}
 var tcp_msg = [...]byte{0xde, 0xad, 0xb1, 0x75} // "dead bits"
 
-func tcp_chop_keys(box *boxPubKey, sig *sigPubKey, link *boxPubKey, bs *[]byte) bool {
-	// This one is pretty simple: we know how long the message should be
-	// So don't call this with a message that's too short
-	if len(*bs) < len(tcp_key)+2*len(*box)+len(*sig) {
-		return false
-	}
-	for idx := range tcp_key {
-		if (*bs)[idx] != tcp_key[idx] {
-			return false
-		}
-	}
-	(*bs) = (*bs)[len(tcp_key):]
-	copy(box[:], *bs)
-	(*bs) = (*bs)[len(box):]
-	copy(sig[:], *bs)
-	(*bs) = (*bs)[len(sig):]
-	copy(link[:], *bs)
-	(*bs) = (*bs)[len(sig):]
-	return true
-}
-
 func tcp_chop_msg(bs *[]byte) ([]byte, bool, error) {
 	// Returns msg, ok, err
 	if len(*bs) < len(tcp_msg) {
diff --git a/src/yggdrasil/version.go b/src/yggdrasil/version.go
new file mode 100644
index 00000000..40a5b965
--- /dev/null
+++ b/src/yggdrasil/version.go
@@ -0,0 +1,70 @@
+package yggdrasil
+
+// This file contains the version metadata struct
+// Used in the inital connection setup and key exchange
+// Some of this could arguably go in wire.go instead
+
+type version_metadata struct {
+	meta [4]byte
+	ver  uint64 // 1 byte in this version
+	// Everything after this point potentially depends on the version number, and is subject to change in future versions
+	minorVer uint64 // 1 byte in this version
+	box      boxPubKey
+	sig      sigPubKey
+	link     boxPubKey
+}
+
+func version_getBaseMetadata() version_metadata {
+	return version_metadata{
+		meta:     [4]byte{'m', 'e', 't', 'a'},
+		ver:      0,
+		minorVer: 2,
+	}
+}
+
+func version_getMetaLength() (mlen int) {
+	mlen += 4            // meta
+	mlen += 1            // ver
+	mlen += 1            // minorVer
+	mlen += boxPubKeyLen // box
+	mlen += sigPubKeyLen // sig
+	mlen += boxPubKeyLen // link
+	return
+}
+
+func (m *version_metadata) encode() []byte {
+	bs := make([]byte, 0, version_getMetaLength())
+	bs = append(bs, m.meta[:]...)
+	bs = append(bs, wire_encode_uint64(m.ver)...)
+	bs = append(bs, wire_encode_uint64(m.minorVer)...)
+	bs = append(bs, m.box[:]...)
+	bs = append(bs, m.sig[:]...)
+	bs = append(bs, m.link[:]...)
+	if len(bs) != version_getMetaLength() {
+		panic("Inconsistent metadata length")
+	}
+	return bs
+}
+
+func (m *version_metadata) decode(bs []byte) bool {
+	switch {
+	case !wire_chop_slice(m.meta[:], &bs):
+		return false
+	case !wire_chop_uint64(&m.ver, &bs):
+		return false
+	case !wire_chop_uint64(&m.minorVer, &bs):
+		return false
+	case !wire_chop_slice(m.box[:], &bs):
+		return false
+	case !wire_chop_slice(m.sig[:], &bs):
+		return false
+	case !wire_chop_slice(m.link[:], &bs):
+		return false
+	}
+	return true
+}
+
+func (m *version_metadata) check() bool {
+	base := version_getBaseMetadata()
+	return base.meta == m.meta && base.ver == m.ver && base.minorVer == m.minorVer
+}
diff --git a/src/yggdrasil/wire.go b/src/yggdrasil/wire.go
index 3b43143b..23e9ab3d 100644
--- a/src/yggdrasil/wire.go
+++ b/src/yggdrasil/wire.go
@@ -66,23 +66,14 @@ func wire_decode_uint64(bs []byte) (uint64, int) {
 }
 
 func wire_intToUint(i int64) uint64 {
-	var u uint64
-	if i < 0 {
-		u = uint64(-i) << 1
-		u |= 0x01 // sign bit
-	} else {
-		u = uint64(i) << 1
-	}
-	return u
+	// Non-negative integers mapped to even integers: 0 -> 0, 1 -> 2, etc.
+	// Negative integres mapped to odd integes: -1 -> 1, -2 -> 3, etc.
+	// This means the least significant bit is a sign bit.
+	return ((uint64(-(i+1))<<1)|0x01)*(uint64(i)>>63) + (uint64(i)<<1)*(^uint64(i)>>63)
 }
 
 func wire_intFromUint(u uint64) int64 {
-	var i int64
-	i = int64(u >> 1)
-	if u&0x01 != 0 {
-		i *= -1
-	}
-	return i
+	return int64(u&0x01)*(-int64(u>>1)-1) + int64(^u&0x01)*int64(u>>1)
 }
 
 ////////////////////////////////////////////////////////////////////////////////