diff --git a/merkle/iavl.go b/merkle/iavl.go
index 02043462e..2d428c360 100644
--- a/merkle/iavl.go
+++ b/merkle/iavl.go
@@ -2,7 +2,8 @@ package merkle
 
 import (
     //"fmt"
-    "hash"
+    "math"
+    //"hash"
     "crypto/sha256"
 )
 
@@ -24,20 +25,24 @@ func (self *IAVLTree) Size() int {
     return self.root.Size()
 }
 
-func (self *IAVLTree) Has(key Sortable) bool {
+func (self *IAVLTree) Has(key Key) bool {
     return self.root.Has(key)
 }
 
-func (self *IAVLTree) Put(key Sortable, value interface{}) (err error) {
+func (self *IAVLTree) Put(key Key, value Value) (err error) {
     self.root, _ = self.root.Put(key, value)
     return nil
 }
 
-func (self *IAVLTree) Get(key Sortable) (value interface{}, err error) {
+func (self *IAVLTree) Hash() []byte {
+    return self.root.Hash()
+}
+
+func (self *IAVLTree) Get(key Key) (value Value, err error) {
     return self.root.Get(key)
 }
 
-func (self *IAVLTree) Remove(key Sortable) (value interface{}, err error) {
+func (self *IAVLTree) Remove(key Key) (value Value, err error) {
     new_root, value, err := self.root.Remove(key)
     if err != nil {
         return nil, err
@@ -49,8 +54,8 @@ func (self *IAVLTree) Remove(key Sortable) (value interface{}, err error) {
 // Node
 
 type IAVLNode struct {
-    key     Sortable
-    value   interface{}
+    key     Key
+    value   Value
     height  int
     hash    []byte
     left    *IAVLNode
@@ -75,7 +80,32 @@ func (self *IAVLNode) Copy(copyHash bool) *IAVLNode {
     }
 }
 
-func (self *IAVLNode) Has(key Sortable) (has bool) {
+func (self *IAVLNode) Key() Key {
+    return self.key
+}
+
+func (self *IAVLNode) Value() Value {
+    return self.value
+}
+
+func (self *IAVLNode) Left() Node {
+    if self.left == nil { return nil }
+    return self.left
+}
+
+func (self *IAVLNode) Right() Node {
+    if self.right == nil { return nil }
+    return self.right
+}
+
+func (self *IAVLNode) Size() int {
+    if self == nil {
+        return 0
+    }
+    return 1 + self.left.Size() + self.right.Size()
+}
+
+func (self *IAVLNode) Has(key Key) (has bool) {
     if self == nil {
         return false
     }
@@ -88,7 +118,7 @@ func (self *IAVLNode) Has(key Sortable) (has bool) {
     }
 }
 
-func (self *IAVLNode) Get(key Sortable) (value interface{}, err error) {
+func (self *IAVLNode) Get(key Key) (value Value, err error) {
     if self == nil {
         return nil, NotFound(key)
     }
@@ -101,6 +131,47 @@ func (self *IAVLNode) Get(key Sortable) (value interface{}, err error) {
     }
 }
 
+func (self *IAVLNode) Hash() []byte {
+    if self == nil {
+        return nil
+    }
+    if self.hash != nil { return self.hash }
+    hasher := sha256.New()
+
+    // node descriptor
+    nodeDesc := byte(0)
+    if self.value != nil { nodeDesc |= 0x01 }
+    if self.left != nil  { nodeDesc |= 0x02 }
+    if self.right != nil { nodeDesc |= 0x04 }
+    hasher.Write([]byte{nodeDesc})
+
+    // node key
+    keyBytes := self.key.Bytes()
+    if len(keyBytes) > 255 { panic("key is too long") }
+    hasher.Write([]byte{byte(len(keyBytes))})
+    hasher.Write(keyBytes)
+
+    // node value
+    if self.value != nil {
+        valueBytes := self.value.Bytes()
+        if len(valueBytes) > math.MaxUint32 { panic("value is too long") }
+        hasher.Write([]byte{byte(len(valueBytes))})
+        hasher.Write(valueBytes)
+    }
+
+    // left child
+    if self.left != nil {
+        hasher.Write(self.left.Hash())
+    }
+
+    // right child
+    if self.right != nil {
+        hasher.Write(self.right.Hash())
+    }
+
+    return hasher.Sum(nil)
+}
+
 // Returns a new tree (unless node is the root) & a copy of the popped node.
 // Can only pop nodes that have one or no children.
 func (self *IAVLNode) pop_node(node *IAVLNode) (new_self, new_node *IAVLNode) {
@@ -231,7 +302,7 @@ func (self *IAVLNode) balance() (new_self *IAVLNode) {
 }
 
 // TODO: don't clear the hash if the value hasn't changed.
-func (self *IAVLNode) Put(key Sortable, value interface{}) (_ *IAVLNode, updated bool) {
+func (self *IAVLNode) Put(key Key, value Value) (_ *IAVLNode, updated bool) {
     if self == nil {
         return &IAVLNode{key: key, value: value, height: 1, hash: nil}, false
     }
@@ -256,7 +327,7 @@ func (self *IAVLNode) Put(key Sortable, value interface{}) (_ *IAVLNode, updated
     }
 }
 
-func (self *IAVLNode) Remove(key Sortable) (new_self *IAVLNode, value interface{}, err error) {
+func (self *IAVLNode) Remove(key Key) (new_self *IAVLNode, value Value, err error) {
     if self == nil {
         return nil, nil, NotFound(key)
     }
@@ -318,32 +389,6 @@ func (self *IAVLNode) Height() int {
     return self.height
 }
 
-func (self *IAVLNode) Size() int {
-    if self == nil {
-        return 0
-    }
-    return 1 + self.left.Size() + self.right.Size()
-}
-
-
-func (self *IAVLNode) Key() Sortable {
-    return self.key
-}
-
-func (self *IAVLNode) Value() interface{} {
-    return self.value
-}
-
-func (self *IAVLNode) Left() Node {
-    if self.left == nil { return nil }
-    return self.left
-}
-
-func (self *IAVLNode) Right() Node {
-    if self.right == nil { return nil }
-    return self.right
-}
-
 // ...
 
 func (self *IAVLNode) _md(side func(*IAVLNode)*IAVLNode) (*IAVLNode) {
@@ -377,14 +422,3 @@ func max(a, b int) int {
     }
     return b
 }
-
-// Calculate the hash of hasher over buf.
-func CalcHash(buf []byte, hasher hash.Hash) []byte {
-    hasher.Write(buf)
-    return hasher.Sum(nil)
-}
-
-// calculate hash256 which is sha256(sha256(data))
-func CalcSha256(buf []byte) []byte {
-    return CalcHash(buf, sha256.New())
-}
diff --git a/merkle/iavl_test.go b/merkle/iavl_test.go
index 94fce5434..ed87e2a60 100644
--- a/merkle/iavl_test.go
+++ b/merkle/iavl_test.go
@@ -50,7 +50,7 @@ func TestImmutableAvlPutHasGetRemove(t *testing.T) {
     records := make([]*record, 400)
     var tree *IAVLNode
     var err error
-    var val interface{}
+    var val Value
     var updated bool
 
     ranrec := func() *record {
@@ -155,7 +155,7 @@ func TestTraversals(t *testing.T) {
     test := func(T Tree) {
         t.Logf("%T", T)
         for j := range order {
-            if err := T.Put(Int(data[order[j]]), order[j]); err != nil {
+            if err := T.Put(Int(data[order[j]]), Int(order[j])); err != nil {
                 t.Error(err)
             }
         }
@@ -174,28 +174,17 @@ func TestTraversals(t *testing.T) {
     test(NewIAVLTree())
 }
 
-func BenchmarkSha256(b *testing.B) {
-    b.StopTimer()
-
-    str := []byte(randstr(32))
-
-    ransha256 := func() []byte {
-        return CalcSha256(str)
-    }
-
-    b.StartTimer()
-    for i := 0; i < b.N; i++ {
-        ransha256()
-    }
-}
-
 // from http://stackoverflow.com/questions/3955680/how-to-check-if-my-avl-tree-implementation-is-correct
 func TestGriffin(t *testing.T) {
+
+    // Convenience for a new node
     N := func(l *IAVLNode, i int, r *IAVLNode) *IAVLNode {
         n := &IAVLNode{Int32(i), nil, -1, nil, l, r}
         n.calc_height()
         return n
     }
+
+    // Convenience for simple printing of keys & tree structure
     var P func(*IAVLNode) string
     P = func(n *IAVLNode) string {
         if n.left == nil && n.right == nil {
@@ -273,3 +262,17 @@ func TestGriffin(t *testing.T) {
     expectRemove(n6, 1, "(((2 3 4) 5 (6 7 -)) 8 (9 10 (- 11 12)))")
 
 }
+
+func TestHash(t *testing.T) {
+
+    // Maybe, construct some tree & determine the number of new hashes calculated.
+    // Make sure the number of new hashings is expected, as well as the hash value.
+    // Then, nuke the hash values and reconstruct, ensure that the resulting hash is the same.
+
+    tree := NewIAVLTree()
+    tree.Put(String("foo"), String("bar"))
+    fmt.Println(tree.Hash())
+
+    tree.Put(String("foo2"), String("bar"))
+    fmt.Println(tree.Hash())
+}
diff --git a/merkle/int.go b/merkle/int.go
index 26115a96c..f16022e87 100644
--- a/merkle/int.go
+++ b/merkle/int.go
@@ -1,5 +1,8 @@
 package merkle
 
+import (
+    "encoding/binary"
+)
 
 type Int8 int8
 type UInt8 uint8
@@ -13,7 +16,7 @@ type Int int
 type UInt uint
 
 
-func (self Int8) Equals(other Sortable) bool {
+func (self Int8) Equals(other Key) bool {
     if o, ok := other.(Int8); ok {
         return self == o
     } else {
@@ -21,7 +24,7 @@ func (self Int8) Equals(other Sortable) bool {
     }
 }
 
-func (self Int8) Less(other Sortable) bool {
+func (self Int8) Less(other Key) bool {
     if o, ok := other.(Int8); ok {
         return self < o
     } else {
@@ -29,12 +32,12 @@ func (self Int8) Less(other Sortable) bool {
     }
 }
 
-func (self Int8) Hash() int {
-    return int(self)
+func (self Int8) Bytes() []byte {
+    return []byte{byte(self)}
 }
 
 
-func (self UInt8) Equals(other Sortable) bool {
+func (self UInt8) Equals(other Key) bool {
     if o, ok := other.(UInt8); ok {
         return self == o
     } else {
@@ -42,7 +45,7 @@ func (self UInt8) Equals(other Sortable) bool {
     }
 }
 
-func (self UInt8) Less(other Sortable) bool {
+func (self UInt8) Less(other Key) bool {
     if o, ok := other.(UInt8); ok {
         return self < o
     } else {
@@ -50,12 +53,12 @@ func (self UInt8) Less(other Sortable) bool {
     }
 }
 
-func (self UInt8) Hash() int {
-    return int(self)
+func (self UInt8) Bytes() []byte {
+    return []byte{byte(self)}
 }
 
 
-func (self Int16) Equals(other Sortable) bool {
+func (self Int16) Equals(other Key) bool {
     if o, ok := other.(Int16); ok {
         return self == o
     } else {
@@ -63,7 +66,7 @@ func (self Int16) Equals(other Sortable) bool {
     }
 }
 
-func (self Int16) Less(other Sortable) bool {
+func (self Int16) Less(other Key) bool {
     if o, ok := other.(Int16); ok {
         return self < o
     } else {
@@ -71,12 +74,14 @@ func (self Int16) Less(other Sortable) bool {
     }
 }
 
-func (self Int16) Hash() int {
-    return int(self)
+func (self Int16) Bytes() []byte {
+    b := [2]byte{}
+    binary.LittleEndian.PutUint16(b[:], uint16(self))
+    return b[:]
 }
 
 
-func (self UInt16) Equals(other Sortable) bool {
+func (self UInt16) Equals(other Key) bool {
     if o, ok := other.(UInt16); ok {
         return self == o
     } else {
@@ -84,7 +89,7 @@ func (self UInt16) Equals(other Sortable) bool {
     }
 }
 
-func (self UInt16) Less(other Sortable) bool {
+func (self UInt16) Less(other Key) bool {
     if o, ok := other.(UInt16); ok {
         return self < o
     } else {
@@ -92,12 +97,14 @@ func (self UInt16) Less(other Sortable) bool {
     }
 }
 
-func (self UInt16) Hash() int {
-    return int(self)
+func (self UInt16) Bytes() []byte {
+    b := [2]byte{}
+    binary.LittleEndian.PutUint16(b[:], uint16(self))
+    return b[:]
 }
 
 
-func (self Int32) Equals(other Sortable) bool {
+func (self Int32) Equals(other Key) bool {
     if o, ok := other.(Int32); ok {
         return self == o
     } else {
@@ -105,7 +112,7 @@ func (self Int32) Equals(other Sortable) bool {
     }
 }
 
-func (self Int32) Less(other Sortable) bool {
+func (self Int32) Less(other Key) bool {
     if o, ok := other.(Int32); ok {
         return self < o
     } else {
@@ -113,12 +120,14 @@ func (self Int32) Less(other Sortable) bool {
     }
 }
 
-func (self Int32) Hash() int {
-    return int(self)
+func (self Int32) Bytes() []byte {
+    b := [4]byte{}
+    binary.LittleEndian.PutUint32(b[:], uint32(self))
+    return b[:]
 }
 
 
-func (self UInt32) Equals(other Sortable) bool {
+func (self UInt32) Equals(other Key) bool {
     if o, ok := other.(UInt32); ok {
         return self == o
     } else {
@@ -126,7 +135,7 @@ func (self UInt32) Equals(other Sortable) bool {
     }
 }
 
-func (self UInt32) Less(other Sortable) bool {
+func (self UInt32) Less(other Key) bool {
     if o, ok := other.(UInt32); ok {
         return self < o
     } else {
@@ -134,12 +143,14 @@ func (self UInt32) Less(other Sortable) bool {
     }
 }
 
-func (self UInt32) Hash() int {
-    return int(self)
+func (self UInt32) Bytes() []byte {
+    b := [4]byte{}
+    binary.LittleEndian.PutUint32(b[:], uint32(self))
+    return b[:]
 }
 
 
-func (self Int64) Equals(other Sortable) bool {
+func (self Int64) Equals(other Key) bool {
     if o, ok := other.(Int64); ok {
         return self == o
     } else {
@@ -147,7 +158,7 @@ func (self Int64) Equals(other Sortable) bool {
     }
 }
 
-func (self Int64) Less(other Sortable) bool {
+func (self Int64) Less(other Key) bool {
     if o, ok := other.(Int64); ok {
         return self < o
     } else {
@@ -155,12 +166,14 @@ func (self Int64) Less(other Sortable) bool {
     }
 }
 
-func (self Int64) Hash() int {
-    return int(self>>32) ^ int(self)
+func (self Int64) Bytes() []byte {
+    b := [8]byte{}
+    binary.LittleEndian.PutUint64(b[:], uint64(self))
+    return b[:]
 }
 
 
-func (self UInt64) Equals(other Sortable) bool {
+func (self UInt64) Equals(other Key) bool {
     if o, ok := other.(UInt64); ok {
         return self == o
     } else {
@@ -168,7 +181,7 @@ func (self UInt64) Equals(other Sortable) bool {
     }
 }
 
-func (self UInt64) Less(other Sortable) bool {
+func (self UInt64) Less(other Key) bool {
     if o, ok := other.(UInt64); ok {
         return self < o
     } else {
@@ -176,12 +189,14 @@ func (self UInt64) Less(other Sortable) bool {
     }
 }
 
-func (self UInt64) Hash() int {
-    return int(self>>32) ^ int(self)
+func (self UInt64) Bytes() []byte {
+    b := [8]byte{}
+    binary.LittleEndian.PutUint64(b[:], uint64(self))
+    return b[:]
 }
 
 
-func (self Int) Equals(other Sortable) bool {
+func (self Int) Equals(other Key) bool {
     if o, ok := other.(Int); ok {
         return self == o
     } else {
@@ -189,7 +204,7 @@ func (self Int) Equals(other Sortable) bool {
     }
 }
 
-func (self Int) Less(other Sortable) bool {
+func (self Int) Less(other Key) bool {
     if o, ok := other.(Int); ok {
         return self < o
     } else {
@@ -197,12 +212,14 @@ func (self Int) Less(other Sortable) bool {
     }
 }
 
-func (self Int) Hash() int {
-    return int(self)
+func (self Int) Bytes() []byte {
+    b := [8]byte{}
+    binary.LittleEndian.PutUint64(b[:], uint64(self))
+    return b[:]
 }
 
 
-func (self UInt) Equals(other Sortable) bool {
+func (self UInt) Equals(other Key) bool {
     if o, ok := other.(UInt); ok {
         return self == o
     } else {
@@ -210,7 +227,7 @@ func (self UInt) Equals(other Sortable) bool {
     }
 }
 
-func (self UInt) Less(other Sortable) bool {
+func (self UInt) Less(other Key) bool {
     if o, ok := other.(UInt); ok {
         return self < o
     } else {
@@ -218,8 +235,8 @@ func (self UInt) Less(other Sortable) bool {
     }
 }
 
-func (self UInt) Hash() int {
-    return int(self)
+func (self UInt) Bytes() []byte {
+    b := [8]byte{}
+    binary.LittleEndian.PutUint64(b[:], uint64(self))
+    return b[:]
 }
-
-
diff --git a/merkle/string.go b/merkle/string.go
index e497f0282..b09ab4a19 100644
--- a/merkle/string.go
+++ b/merkle/string.go
@@ -5,7 +5,7 @@ import "bytes"
 type String string
 type ByteSlice []byte
 
-func (self String) Equals(other Sortable) bool {
+func (self String) Equals(other Key) bool {
     if o, ok := other.(String); ok {
         return self == o
     } else {
@@ -13,7 +13,7 @@ func (self String) Equals(other Sortable) bool {
     }
 }
 
-func (self String) Less(other Sortable) bool {
+func (self String) Less(other Key) bool {
     if o, ok := other.(String); ok {
         return self < o
     } else {
@@ -21,16 +21,11 @@ func (self String) Less(other Sortable) bool {
     }
 }
 
-func (self String) Hash() int {
-    bytes := []byte(self)
-    hash := 0
-    for i, c := range bytes {
-        hash += (i+1)*int(c)
-    }
-    return hash
+func (self String) Bytes() []byte {
+    return []byte(self)
 }
 
-func (self ByteSlice) Equals(other Sortable) bool {
+func (self ByteSlice) Equals(other Key) bool {
     if o, ok := other.(ByteSlice); ok {
         return bytes.Equal(self, o)
     } else {
@@ -38,7 +33,7 @@ func (self ByteSlice) Equals(other Sortable) bool {
     }
 }
 
-func (self ByteSlice) Less(other Sortable) bool {
+func (self ByteSlice) Less(other Key) bool {
     if o, ok := other.(ByteSlice); ok {
         return bytes.Compare(self, o) < 0 // -1 if a < b
     } else {
@@ -46,12 +41,6 @@ func (self ByteSlice) Less(other Sortable) bool {
     }
 }
 
-func (self ByteSlice) Hash() int {
-    hash := 0
-    for i, c := range self {
-        hash += (i+1)*int(c)
-    }
-    return hash
+func (self ByteSlice) Bytes() []byte {
+    return []byte(self)
 }
-
-
diff --git a/merkle/types.go b/merkle/types.go
index a7bb33ee9..625af68ee 100644
--- a/merkle/types.go
+++ b/merkle/types.go
@@ -4,38 +4,45 @@ import (
     "fmt"
 )
 
-type Sortable interface {
-    Equals(b Sortable) bool
-    Less(b Sortable) bool
+type Value interface {
+    Bytes() []byte
+}
+
+type Key interface {
+    Equals(b Key) bool
+    Less(b Key) bool
+    Bytes() []byte
 }
 
 type Tree interface {
     Root() Node
 
     Size() int
-    Has(key Sortable) bool
-    Get(key Sortable) (value interface{}, err error)
+    Has(key Key) bool
+    Get(key Key) (value Value, err error)
+    Hash() []byte
 
-    Put(key Sortable, value interface{}) (err error)
-    Remove(key Sortable) (value interface{}, err error)
+    Put(key Key, value Value) (err error)
+    Remove(key Key) (value Value, err error)
 }
 
 type Node interface {
-    Key() Sortable
-    Value() interface{}
-    Left() Node
+    Key()   Key
+    Value() Value
+    Left()  Node
     Right() Node
 
     Size() int
-    Has(key Sortable) bool
-    Get(key Sortable) (value interface{}, err error)
+    Has(key Key) bool
+    Get(key Key) (value Value, err error)
+    Hash() []byte
 
-    Put(key Sortable, value interface{}) (_ *IAVLNode, updated bool)
-    Remove(key Sortable) (_ *IAVLNode, value interface{}, err error)
+    Put(key Key, value Value) (_ *IAVLNode, updated bool)
+    Remove(key Key) (_ *IAVLNode, value Value, err error)
 }
 
 type NodeIterator func() (node Node, next NodeIterator)
 
-func NotFound(key Sortable) error {
+func NotFound(key Key) error {
     return fmt.Errorf("Key was not found.")
 }