diff --git a/account/priv_account.go b/account/priv_account.go
index 92a7cb36..77351e53 100644
--- a/account/priv_account.go
+++ b/account/priv_account.go
@@ -28,7 +28,7 @@ func GenPrivAccount() *PrivAccount {
 
 // Generates a new account with private key from SHA256 hash of a secret
 func GenPrivAccountFromSecret(secret []byte) *PrivAccount {
-	privKey32 := binary.BinarySha256(secret)
+	privKey32 := binary.BinarySha256(secret) // Not Ripemd160 because we want 32 bytes.
 	privKeyBytes := new([64]byte)
 	copy(privKeyBytes[:32], privKey32)
 	pubKeyBytes := ed25519.MakePublicKey(privKeyBytes)
diff --git a/binary/util.go b/binary/util.go
index 29aa57cd..d03464bf 100644
--- a/binary/util.go
+++ b/binary/util.go
@@ -40,6 +40,7 @@ func BinaryCompare(a, b interface{}) int {
 	return bytes.Compare(aBytes, bBytes)
 }
 
+// NOTE: only use this if you need 32 bytes.
 func BinarySha256(o interface{}) []byte {
 	hasher, n, err := sha256.New(), new(int64), new(error)
 	WriteBinary(o, hasher, n, err)
@@ -49,6 +50,7 @@ func BinarySha256(o interface{}) []byte {
 	return hasher.Sum(nil)
 }
 
+// NOTE: The default hash function is Ripemd160.
 func BinaryRipemd160(o interface{}) []byte {
 	hasher, n, err := ripemd160.New(), new(int64), new(error)
 	WriteBinary(o, hasher, n, err)
diff --git a/mempool/mempool.go b/mempool/mempool.go
index 51cfab13..a08d9bc6 100644
--- a/mempool/mempool.go
+++ b/mempool/mempool.go
@@ -11,7 +11,6 @@ package mempool
 import (
 	"sync"
 
-	"github.com/tendermint/tendermint/binary"
 	sm "github.com/tendermint/tendermint/state"
 	"github.com/tendermint/tendermint/types"
 )
@@ -73,19 +72,18 @@ func (mem *Mempool) ResetForBlockAndState(block *types.Block, state *sm.State) {
 	// First, create a lookup map of txns in new block.
 	blockTxsMap := make(map[string]struct{})
 	for _, tx := range block.Data.Txs {
-		txHash := binary.BinarySha256(tx)
-		blockTxsMap[string(txHash)] = struct{}{}
+		blockTxsMap[string(types.TxID(state.ChainID, tx))] = struct{}{}
 	}
 
 	// Next, filter all txs from mem.txs that are in blockTxsMap
 	txs := []types.Tx{}
 	for _, tx := range mem.txs {
-		txHash := binary.BinarySha256(tx)
-		if _, ok := blockTxsMap[string(txHash)]; ok {
-			log.Debug("Filter out, already committed", "tx", tx, "txHash", txHash)
+		txID := types.TxID(state.ChainID, tx)
+		if _, ok := blockTxsMap[string(txID)]; ok {
+			log.Debug("Filter out, already committed", "tx", tx, "txID", txID)
 			continue
 		} else {
-			log.Debug("Filter in, still new", "tx", tx, "txHash", txHash)
+			log.Debug("Filter in, still new", "tx", tx, "txID", txID)
 			txs = append(txs, tx)
 		}
 	}
diff --git a/merkle/iavl_node.go b/merkle/iavl_node.go
index 6786e9d2..0055f671 100644
--- a/merkle/iavl_node.go
+++ b/merkle/iavl_node.go
@@ -2,7 +2,7 @@ package merkle
 
 import (
 	"bytes"
-	"crypto/sha256"
+	"github.com/tendermint/tendermint/Godeps/_workspace/src/code.google.com/p/go.crypto/ripemd160"
 	"io"
 
 	"github.com/tendermint/tendermint/binary"
@@ -132,7 +132,7 @@ func (node *IAVLNode) hashWithCount(t *IAVLTree) ([]byte, int) {
 		return node.hash, 0
 	}
 
-	hasher := sha256.New()
+	hasher := ripemd160.New()
 	buf := new(bytes.Buffer)
 	_, hashCount, err := node.writeHashBytes(t, buf)
 	if err != nil {
diff --git a/merkle/iavl_proof.go b/merkle/iavl_proof.go
index 0541aa73..4216c6c1 100644
--- a/merkle/iavl_proof.go
+++ b/merkle/iavl_proof.go
@@ -2,7 +2,9 @@ package merkle
 
 import (
 	"bytes"
-	"crypto/sha256"
+
+	"github.com/tendermint/tendermint/Godeps/_workspace/src/code.google.com/p/go.crypto/ripemd160"
+
 	"github.com/tendermint/tendermint/binary"
 	. "github.com/tendermint/tendermint/common"
 )
@@ -41,7 +43,7 @@ type IAVLProofInnerNode struct {
 }
 
 func (branch IAVLProofInnerNode) Hash(childHash []byte) []byte {
-	hasher := sha256.New()
+	hasher := ripemd160.New()
 	buf := new(bytes.Buffer)
 	n, err := int64(0), error(nil)
 	binary.WriteInt8(branch.Height, buf, &n, &err)
@@ -67,7 +69,7 @@ type IAVLProofLeafNode struct {
 }
 
 func (leaf IAVLProofLeafNode) Hash() []byte {
-	hasher := sha256.New()
+	hasher := ripemd160.New()
 	buf := new(bytes.Buffer)
 	n, err := int64(0), error(nil)
 	binary.WriteInt8(0, buf, &n, &err)
diff --git a/merkle/simple_tree.go b/merkle/simple_tree.go
index 941ddb5c..ad75393c 100644
--- a/merkle/simple_tree.go
+++ b/merkle/simple_tree.go
@@ -26,16 +26,17 @@ package merkle
 
 import (
 	"bytes"
-	"crypto/sha256"
 	"fmt"
 
+	"github.com/tendermint/tendermint/Godeps/_workspace/src/code.google.com/p/go.crypto/ripemd160"
+
 	"github.com/tendermint/tendermint/binary"
 )
 
 func SimpleHashFromTwoHashes(left []byte, right []byte) []byte {
 	var n int64
 	var err error
-	var hasher = sha256.New()
+	var hasher = ripemd160.New()
 	binary.WriteByteSlice(left, hasher, &n, &err)
 	binary.WriteByteSlice(right, hasher, &n, &err)
 	if err != nil {
@@ -69,7 +70,7 @@ func SimpleHashFromBinaries(items []interface{}) []byte {
 
 // General Convenience
 func SimpleHashFromBinary(item interface{}) []byte {
-	hasher, n, err := sha256.New(), new(int64), new(error)
+	hasher, n, err := ripemd160.New(), new(int64), new(error)
 	binary.WriteBinary(item, hasher, n, err)
 	if *err != nil {
 		panic(err)
diff --git a/state/validator.go b/state/validator.go
index 20f12532..1519ea68 100644
--- a/state/validator.go
+++ b/state/validator.go
@@ -98,7 +98,7 @@ func (v *Validator) String() string {
 }
 
 func (v *Validator) Hash() []byte {
-	return binary.BinarySha256(v)
+	return binary.BinaryRipemd160(v)
 }
 
 //-------------------------------------
diff --git a/types/block.go b/types/block.go
index c34387a8..c67674ab 100644
--- a/types/block.go
+++ b/types/block.go
@@ -2,7 +2,6 @@ package types
 
 import (
 	"bytes"
-	"crypto/sha256"
 	"errors"
 	"fmt"
 	"strings"
@@ -138,15 +137,7 @@ func (h *Header) Hash() []byte {
 		return nil
 	}
 
-	buf := new(bytes.Buffer)
-	hasher, n, err := sha256.New(), new(int64), new(error)
-	binary.WriteBinary(h, buf, n, err)
-	if *err != nil {
-		panic(err)
-	}
-	hasher.Write(buf.Bytes())
-	hash := hasher.Sum(nil)
-	return hash
+	return binary.BinaryRipemd160(h)
 }
 
 func (h *Header) StringIndented(indent string) string {
@@ -321,7 +312,7 @@ func (data *Data) Hash() []byte {
 		for i, tx := range data.Txs {
 			bs[i] = account.SignBytes(config.GetString("chain_id"), tx)
 		}
-		data.hash = merkle.SimpleHashFromBinaries(bs)
+		data.hash = merkle.SimpleHashFromBinaries(bs) // NOTE: leaves are TxIDs.
 	}
 	return data.hash
 }
diff --git a/types/part_set.go b/types/part_set.go
index 8d4ba320..32803fb2 100644
--- a/types/part_set.go
+++ b/types/part_set.go
@@ -2,12 +2,13 @@ package types
 
 import (
 	"bytes"
-	"crypto/sha256"
 	"errors"
 	"fmt"
 	"io"
 	"sync"
 
+	"github.com/tendermint/tendermint/Godeps/_workspace/src/code.google.com/p/go.crypto/ripemd160"
+
 	"github.com/tendermint/tendermint/binary"
 	. "github.com/tendermint/tendermint/common"
 	"github.com/tendermint/tendermint/merkle"
@@ -34,7 +35,7 @@ func (part *Part) Hash() []byte {
 	if part.hash != nil {
 		return part.hash
 	} else {
-		hasher := sha256.New()
+		hasher := ripemd160.New()
 		_, err := hasher.Write(part.Bytes)
 		if err != nil {
 			panic(err)
diff --git a/types/tx.go b/types/tx.go
index 36c91082..552485a9 100644
--- a/types/tx.go
+++ b/types/tx.go
@@ -314,8 +314,7 @@ func (tx *DupeoutTx) String() string {
 
 //-----------------------------------------------------------------------------
 
-// NOTE: the tx merkle tree uses sha256, so this TxID is really just for
-// reference when using the rpc and catching events
+// This should match the leaf hashes of Block.Data.Hash()'s SimpleMerkleTree.
 func TxID(chainID string, tx Tx) []byte {
 	signBytes := account.SignBytes(chainID, tx)
 	return binary.BinaryRipemd160(signBytes)