diff --git a/merkle/README.md b/merkle/README.md
new file mode 100644
index 00000000..c4497836
--- /dev/null
+++ b/merkle/README.md
@@ -0,0 +1,4 @@
+## Simple Merkle Tree
+
+For smaller static data structures that don't require immutable snapshots or mutability; 
+for instance the transactions and validation signatures of a block can be hashed using this simple merkle tree logic.
diff --git a/merkle/simple_map.go b/merkle/simple_map.go
new file mode 100644
index 00000000..cd38de76
--- /dev/null
+++ b/merkle/simple_map.go
@@ -0,0 +1,84 @@
+package merkle
+
+import (
+	cmn "github.com/tendermint/tmlibs/common"
+	"golang.org/x/crypto/ripemd160"
+)
+
+type SimpleMap struct {
+	kvs    cmn.KVPairs
+	sorted bool
+}
+
+func NewSimpleMap() *SimpleMap {
+	return &SimpleMap{
+		kvs:    nil,
+		sorted: false,
+	}
+}
+
+func (sm *SimpleMap) Set(key string, value Hasher) {
+	sm.sorted = false
+
+	// Hash the key to blind it... why not?
+	khash := SimpleHashFromBytes([]byte(key))
+
+	// And the value is hashed too, so you can
+	// check for equality with a cached value (say)
+	// and make a determination to fetch or not.
+	vhash := value.Hash()
+
+	sm.kvs = append(sm.kvs, cmn.KVPair{
+		Key:   khash,
+		Value: vhash,
+	})
+}
+
+// Merkle root hash of items sorted by key
+// (UNSTABLE: and by value too if duplicate key).
+func (sm *SimpleMap) Hash() []byte {
+	sm.Sort()
+	return hashKVPairs(sm.kvs)
+}
+
+func (sm *SimpleMap) Sort() {
+	if sm.sorted {
+		return
+	}
+	sm.kvs.Sort()
+	sm.sorted = true
+}
+
+// Returns a copy of sorted KVPairs.
+func (sm *SimpleMap) KVPairs() cmn.KVPairs {
+	sm.Sort()
+	kvs := make(cmn.KVPairs, len(sm.kvs))
+	copy(kvs, sm.kvs)
+	return kvs
+}
+
+//----------------------------------------
+
+// A local extension to KVPair that can be hashed.
+type KVPair cmn.KVPair
+
+func (kv KVPair) Hash() []byte {
+	hasher := ripemd160.New()
+	err := encodeByteSlice(hasher, kv.Key)
+	if err != nil {
+		panic(err)
+	}
+	err = encodeByteSlice(hasher, kv.Value)
+	if err != nil {
+		panic(err)
+	}
+	return hasher.Sum(nil)
+}
+
+func hashKVPairs(kvs cmn.KVPairs) []byte {
+	kvsH := make([]Hasher, 0, len(kvs))
+	for _, kvp := range kvs {
+		kvsH = append(kvsH, KVPair(kvp))
+	}
+	return SimpleHashFromHashers(kvsH)
+}
diff --git a/merkle/simple_map_test.go b/merkle/simple_map_test.go
new file mode 100644
index 00000000..c9c87135
--- /dev/null
+++ b/merkle/simple_map_test.go
@@ -0,0 +1,53 @@
+package merkle
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+type strHasher string
+
+func (str strHasher) Hash() []byte {
+	return SimpleHashFromBytes([]byte(str))
+}
+
+func TestSimpleMap(t *testing.T) {
+	{
+		db := NewSimpleMap()
+		db.Set("key1", strHasher("value1"))
+		assert.Equal(t, "acdb4f121bc6f25041eb263ab463f1cd79236a32", fmt.Sprintf("%x", db.Hash()), "Hash didn't match")
+	}
+	{
+		db := NewSimpleMap()
+		db.Set("key1", strHasher("value2"))
+		assert.Equal(t, "b8cbf5adee8c524e14f531da9b49adbbbd66fffa", fmt.Sprintf("%x", db.Hash()), "Hash didn't match")
+	}
+	{
+		db := NewSimpleMap()
+		db.Set("key1", strHasher("value1"))
+		db.Set("key2", strHasher("value2"))
+		assert.Equal(t, "1708aabc85bbe00242d3db8c299516aa54e48c38", fmt.Sprintf("%x", db.Hash()), "Hash didn't match")
+	}
+	{
+		db := NewSimpleMap()
+		db.Set("key2", strHasher("value2")) // NOTE: out of order
+		db.Set("key1", strHasher("value1"))
+		assert.Equal(t, "1708aabc85bbe00242d3db8c299516aa54e48c38", fmt.Sprintf("%x", db.Hash()), "Hash didn't match")
+	}
+	{
+		db := NewSimpleMap()
+		db.Set("key1", strHasher("value1"))
+		db.Set("key2", strHasher("value2"))
+		db.Set("key3", strHasher("value3"))
+		assert.Equal(t, "e728afe72ce351eed6aca65c5f78da19b9a6e214", fmt.Sprintf("%x", db.Hash()), "Hash didn't match")
+	}
+	{
+		db := NewSimpleMap()
+		db.Set("key2", strHasher("value2")) // NOTE: out of order
+		db.Set("key1", strHasher("value1"))
+		db.Set("key3", strHasher("value3"))
+		assert.Equal(t, "e728afe72ce351eed6aca65c5f78da19b9a6e214", fmt.Sprintf("%x", db.Hash()), "Hash didn't match")
+	}
+}
diff --git a/merkle/simple_proof.go b/merkle/simple_proof.go
new file mode 100644
index 00000000..ca6ccf37
--- /dev/null
+++ b/merkle/simple_proof.go
@@ -0,0 +1,144 @@
+package merkle
+
+import (
+	"bytes"
+	"fmt"
+)
+
+type SimpleProof struct {
+	Aunts [][]byte `json:"aunts"` // Hashes from leaf's sibling to a root's child.
+}
+
+// proofs[0] is the proof for items[0].
+func SimpleProofsFromHashers(items []Hasher) (rootHash []byte, proofs []*SimpleProof) {
+	trails, rootSPN := trailsFromHashers(items)
+	rootHash = rootSPN.Hash
+	proofs = make([]*SimpleProof, len(items))
+	for i, trail := range trails {
+		proofs[i] = &SimpleProof{
+			Aunts: trail.FlattenAunts(),
+		}
+	}
+	return
+}
+
+func SimpleProofsFromMap(m map[string]Hasher) (rootHash []byte, proofs []*SimpleProof) {
+	sm := NewSimpleMap()
+	for k, v := range m {
+		sm.Set(k, v)
+	}
+	sm.Sort()
+	kvs := sm.kvs
+	kvsH := make([]Hasher, 0, len(kvs))
+	for _, kvp := range kvs {
+		kvsH = append(kvsH, KVPair(kvp))
+	}
+	return SimpleProofsFromHashers(kvsH)
+}
+
+// Verify that leafHash is a leaf hash of the simple-merkle-tree
+// which hashes to rootHash.
+func (sp *SimpleProof) Verify(index int, total int, leafHash []byte, rootHash []byte) bool {
+	computedHash := computeHashFromAunts(index, total, leafHash, sp.Aunts)
+	return computedHash != nil && bytes.Equal(computedHash, rootHash)
+}
+
+func (sp *SimpleProof) String() string {
+	return sp.StringIndented("")
+}
+
+func (sp *SimpleProof) StringIndented(indent string) string {
+	return fmt.Sprintf(`SimpleProof{
+%s  Aunts: %X
+%s}`,
+		indent, sp.Aunts,
+		indent)
+}
+
+// Use the leafHash and innerHashes to get the root merkle hash.
+// If the length of the innerHashes slice isn't exactly correct, the result is nil.
+// Recursive impl.
+func computeHashFromAunts(index int, total int, leafHash []byte, innerHashes [][]byte) []byte {
+	if index >= total || index < 0 || total <= 0 {
+		return nil
+	}
+	switch total {
+	case 0:
+		panic("Cannot call computeHashFromAunts() with 0 total")
+	case 1:
+		if len(innerHashes) != 0 {
+			return nil
+		}
+		return leafHash
+	default:
+		if len(innerHashes) == 0 {
+			return nil
+		}
+		numLeft := (total + 1) / 2
+		if index < numLeft {
+			leftHash := computeHashFromAunts(index, numLeft, leafHash, innerHashes[:len(innerHashes)-1])
+			if leftHash == nil {
+				return nil
+			}
+			return SimpleHashFromTwoHashes(leftHash, innerHashes[len(innerHashes)-1])
+		}
+		rightHash := computeHashFromAunts(index-numLeft, total-numLeft, leafHash, innerHashes[:len(innerHashes)-1])
+		if rightHash == nil {
+			return nil
+		}
+		return SimpleHashFromTwoHashes(innerHashes[len(innerHashes)-1], rightHash)
+	}
+}
+
+// Helper structure to construct merkle proof.
+// The node and the tree is thrown away afterwards.
+// Exactly one of node.Left and node.Right is nil, unless node is the root, in which case both are nil.
+// node.Parent.Hash = hash(node.Hash, node.Right.Hash) or
+// hash(node.Left.Hash, node.Hash), depending on whether node is a left/right child.
+type SimpleProofNode struct {
+	Hash   []byte
+	Parent *SimpleProofNode
+	Left   *SimpleProofNode // Left sibling  (only one of Left,Right is set)
+	Right  *SimpleProofNode // Right sibling (only one of Left,Right is set)
+}
+
+// Starting from a leaf SimpleProofNode, FlattenAunts() will return
+// the inner hashes for the item corresponding to the leaf.
+func (spn *SimpleProofNode) FlattenAunts() [][]byte {
+	// Nonrecursive impl.
+	innerHashes := [][]byte{}
+	for spn != nil {
+		if spn.Left != nil {
+			innerHashes = append(innerHashes, spn.Left.Hash)
+		} else if spn.Right != nil {
+			innerHashes = append(innerHashes, spn.Right.Hash)
+		} else {
+			break
+		}
+		spn = spn.Parent
+	}
+	return innerHashes
+}
+
+// trails[0].Hash is the leaf hash for items[0].
+// trails[i].Parent.Parent....Parent == root for all i.
+func trailsFromHashers(items []Hasher) (trails []*SimpleProofNode, root *SimpleProofNode) {
+	// Recursive impl.
+	switch len(items) {
+	case 0:
+		return nil, nil
+	case 1:
+		trail := &SimpleProofNode{items[0].Hash(), nil, nil, nil}
+		return []*SimpleProofNode{trail}, trail
+	default:
+		lefts, leftRoot := trailsFromHashers(items[:(len(items)+1)/2])
+		rights, rightRoot := trailsFromHashers(items[(len(items)+1)/2:])
+		rootHash := SimpleHashFromTwoHashes(leftRoot.Hash, rightRoot.Hash)
+		root := &SimpleProofNode{rootHash, nil, nil, nil}
+		leftRoot.Parent = root
+		leftRoot.Right = rightRoot
+		rightRoot.Parent = root
+		rightRoot.Left = leftRoot
+		return append(lefts, rights...), root
+	}
+}
diff --git a/merkle/simple_tree.go b/merkle/simple_tree.go
new file mode 100644
index 00000000..9bdf52cb
--- /dev/null
+++ b/merkle/simple_tree.go
@@ -0,0 +1,91 @@
+/*
+Computes a deterministic minimal height merkle tree hash.
+If the number of items is not a power of two, some leaves
+will be at different levels. Tries to keep both sides of
+the tree the same size, but the left may be one greater.
+
+Use this for short deterministic trees, such as the validator list.
+For larger datasets, use IAVLTree.
+
+                        *
+                       / \
+                     /     \
+                   /         \
+                 /             \
+                *               *
+               / \             / \
+              /   \           /   \
+             /     \         /     \
+            *       *       *       h6
+           / \     / \     / \
+          h0  h1  h2  h3  h4  h5
+
+*/
+
+package merkle
+
+import (
+	"golang.org/x/crypto/ripemd160"
+)
+
+func SimpleHashFromTwoHashes(left []byte, right []byte) []byte {
+	var hasher = ripemd160.New()
+	err := encodeByteSlice(hasher, left)
+	if err != nil {
+		panic(err)
+	}
+	err = encodeByteSlice(hasher, right)
+	if err != nil {
+		panic(err)
+	}
+	return hasher.Sum(nil)
+}
+
+func SimpleHashFromHashes(hashes [][]byte) []byte {
+	// Recursive impl.
+	switch len(hashes) {
+	case 0:
+		return nil
+	case 1:
+		return hashes[0]
+	default:
+		left := SimpleHashFromHashes(hashes[:(len(hashes)+1)/2])
+		right := SimpleHashFromHashes(hashes[(len(hashes)+1)/2:])
+		return SimpleHashFromTwoHashes(left, right)
+	}
+}
+
+// NOTE: Do not implement this, use SimpleHashFromByteslices instead.
+// type Byteser interface { Bytes() []byte }
+// func SimpleHashFromBytesers(items []Byteser) []byte { ... }
+
+func SimpleHashFromByteslices(bzs [][]byte) []byte {
+	hashes := make([][]byte, len(bzs))
+	for i, bz := range bzs {
+		hashes[i] = SimpleHashFromBytes(bz)
+	}
+	return SimpleHashFromHashes(hashes)
+}
+
+func SimpleHashFromBytes(bz []byte) []byte {
+	hasher := ripemd160.New()
+	hasher.Write(bz)
+	return hasher.Sum(nil)
+}
+
+func SimpleHashFromHashers(items []Hasher) []byte {
+	hashes := make([][]byte, len(items))
+	for i, item := range items {
+		hash := item.Hash()
+		hashes[i] = hash
+	}
+	return SimpleHashFromHashes(hashes)
+}
+
+func SimpleHashFromMap(m map[string]Hasher) []byte {
+	sm := NewSimpleMap()
+	for k, v := range m {
+		sm.Set(k, v)
+	}
+	return sm.Hash()
+}
diff --git a/merkle/simple_tree_test.go b/merkle/simple_tree_test.go
new file mode 100644
index 00000000..8c4ed01f
--- /dev/null
+++ b/merkle/simple_tree_test.go
@@ -0,0 +1,87 @@
+package merkle
+
+import (
+	"bytes"
+
+	cmn "github.com/tendermint/tmlibs/common"
+	. "github.com/tendermint/tmlibs/test"
+
+	"testing"
+)
+
+type testItem []byte
+
+func (tI testItem) Hash() []byte {
+	return []byte(tI)
+}
+
+func TestSimpleProof(t *testing.T) {
+
+	total := 100
+
+	items := make([]Hasher, total)
+	for i := 0; i < total; i++ {
+		items[i] = testItem(cmn.RandBytes(32))
+	}
+
+	rootHash := SimpleHashFromHashers(items)
+
+	rootHash2, proofs := SimpleProofsFromHashers(items)
+
+	if !bytes.Equal(rootHash, rootHash2) {
+		t.Errorf("Unmatched root hashes: %X vs %X", rootHash, rootHash2)
+	}
+
+	// For each item, check the trail.
+	for i, item := range items {
+		itemHash := item.Hash()
+		proof := proofs[i]
+
+		// Verify success
+		ok := proof.Verify(i, total, itemHash, rootHash)
+		if !ok {
+			t.Errorf("Verification failed for index %v.", i)
+		}
+
+		// Wrong item index should make it fail
+		{
+			ok = proof.Verify((i+1)%total, total, itemHash, rootHash)
+			if ok {
+				t.Errorf("Expected verification to fail for wrong index %v.", i)
+			}
+		}
+
+		// Trail too long should make it fail
+		origAunts := proof.Aunts
+		proof.Aunts = append(proof.Aunts, cmn.RandBytes(32))
+		{
+			ok = proof.Verify(i, total, itemHash, rootHash)
+			if ok {
+				t.Errorf("Expected verification to fail for wrong trail length.")
+			}
+		}
+		proof.Aunts = origAunts
+
+		// Trail too short should make it fail
+		proof.Aunts = proof.Aunts[0 : len(proof.Aunts)-1]
+		{
+			ok = proof.Verify(i, total, itemHash, rootHash)
+			if ok {
+				t.Errorf("Expected verification to fail for wrong trail length.")
+			}
+		}
+		proof.Aunts = origAunts
+
+		// Mutating the itemHash should make it fail.
+		ok = proof.Verify(i, total, MutateByteSlice(itemHash), rootHash)
+		if ok {
+			t.Errorf("Expected verification to fail for mutated leaf hash")
+		}
+
+		// Mutating the rootHash should make it fail.
+		ok = proof.Verify(i, total, itemHash, MutateByteSlice(rootHash))
+		if ok {
+			t.Errorf("Expected verification to fail for mutated root hash")
+		}
+	}
+}
diff --git a/merkle/types.go b/merkle/types.go
new file mode 100644
index 00000000..a0c491a7
--- /dev/null
+++ b/merkle/types.go
@@ -0,0 +1,47 @@
+package merkle
+
+import (
+	"encoding/binary"
+	"io"
+)
+
+type Tree interface {
+	Size() (size int)
+	Height() (height int8)
+	Has(key []byte) (has bool)
+	Proof(key []byte) (value []byte, proof []byte, exists bool) // TODO make it return an index
+	Get(key []byte) (index int, value []byte, exists bool)
+	GetByIndex(index int) (key []byte, value []byte)
+	Set(key []byte, value []byte) (updated bool)
+	Remove(key []byte) (value []byte, removed bool)
+	HashWithCount() (hash []byte, count int)
+	Hash() (hash []byte)
+	Save() (hash []byte)
+	Load(hash []byte)
+	Copy() Tree
+	Iterate(func(key []byte, value []byte) (stop bool)) (stopped bool)
+	IterateRange(start []byte, end []byte, ascending bool, fx func(key []byte, value []byte) (stop bool)) (stopped bool)
+}
+
+type Hasher interface {
+	Hash() []byte
+}
+
+//-----------------------------------------------------------------------
+// NOTE: these are duplicated from go-amino so we dont need go-amino as a dep
+
+func encodeByteSlice(w io.Writer, bz []byte) (err error) {
+	err = encodeUvarint(w, uint64(len(bz)))
+	if err != nil {
+		return
+	}
+	_, err = w.Write(bz)
+	return
+}
+
+func encodeUvarint(w io.Writer, i uint64) (err error) {
+	var buf [10]byte
+	n := binary.PutUvarint(buf[:], i)
+	_, err = w.Write(buf[0:n])
+	return
+}