diff --git a/sha3/sha3.go b/sha3/sha3.go
index afedde5..bda574e 100644
--- a/sha3/sha3.go
+++ b/sha3/sha3.go
@@ -4,6 +4,14 @@
 
 package sha3
 
+import (
+	"crypto/subtle"
+	"encoding/binary"
+	"unsafe"
+
+	"golang.org/x/sys/cpu"
+)
+
 // spongeDirection indicates the direction bytes are flowing through the sponge.
 type spongeDirection int
 
@@ -14,16 +22,13 @@ const (
 	spongeSqueezing
 )
 
-const (
-	// maxRate is the maximum size of the internal buffer. SHAKE-256
-	// currently needs the largest buffer.
-	maxRate = 168
-)
-
 type state struct {
-	// Generic sponge components.
-	a    [25]uint64 // main state of the hash
-	rate int        // the number of bytes of state to use
+	a [1600 / 8]byte // main state of the hash
+
+	// a[n:rate] is the buffer. If absorbing, it's the remaining space to XOR
+	// into before running the permutation. If squeezing, it's the remaining
+	// output to produce before running the permutation.
+	n, rate int
 
 	// dsbyte contains the "domain separation" bits and the first bit of
 	// the padding. Sections 6.1 and 6.2 of [1] separate the outputs of the
@@ -39,10 +44,6 @@ type state struct {
 	//      Extendable-Output Functions (May 2014)"
 	dsbyte byte
 
-	i, n    int // storage[i:n] is the buffer, i is only used while squeezing
-	storage [maxRate]byte
-
-	// Specific to SHA-3 and SHAKE.
 	outputLen int             // the default output size in bytes
 	state     spongeDirection // whether the sponge is absorbing or squeezing
 }
@@ -61,7 +62,7 @@ func (d *state) Reset() {
 		d.a[i] = 0
 	}
 	d.state = spongeAbsorbing
-	d.i, d.n = 0, 0
+	d.n = 0
 }
 
 func (d *state) clone() *state {
@@ -69,22 +70,25 @@ func (d *state) clone() *state {
 	return &ret
 }
 
-// permute applies the KeccakF-1600 permutation. It handles
-// any input-output buffering.
+// permute applies the KeccakF-1600 permutation.
 func (d *state) permute() {
-	switch d.state {
-	case spongeAbsorbing:
-		// If we're absorbing, we need to xor the input into the state
-		// before applying the permutation.
-		xorIn(d, d.storage[:d.rate])
-		d.n = 0
-		keccakF1600(&d.a)
-	case spongeSqueezing:
-		// If we're squeezing, we need to apply the permutation before
-		// copying more output.
-		keccakF1600(&d.a)
-		d.i = 0
-		copyOut(d, d.storage[:d.rate])
+	var a *[25]uint64
+	if cpu.IsBigEndian {
+		a = new([25]uint64)
+		for i := range a {
+			a[i] = binary.LittleEndian.Uint64(d.a[i*8:])
+		}
+	} else {
+		a = (*[25]uint64)(unsafe.Pointer(&d.a))
+	}
+
+	keccakF1600(a)
+	d.n = 0
+
+	if cpu.IsBigEndian {
+		for i := range a {
+			binary.LittleEndian.PutUint64(d.a[i*8:], a[i])
+		}
 	}
 }
 
@@ -92,53 +96,36 @@ func (d *state) permute() {
 // the multi-bitrate 10..1 padding rule, and permutes the state.
 func (d *state) padAndPermute() {
 	// Pad with this instance's domain-separator bits. We know that there's
-	// at least one byte of space in d.buf because, if it were full,
+	// at least one byte of space in the sponge because, if it were full,
 	// permute would have been called to empty it. dsbyte also contains the
 	// first one bit for the padding. See the comment in the state struct.
-	d.storage[d.n] = d.dsbyte
-	d.n++
-	for d.n < d.rate {
-		d.storage[d.n] = 0
-		d.n++
-	}
+	d.a[d.n] ^= d.dsbyte
 	// This adds the final one bit for the padding. Because of the way that
 	// bits are numbered from the LSB upwards, the final bit is the MSB of
 	// the last byte.
-	d.storage[d.rate-1] ^= 0x80
+	d.a[d.rate-1] ^= 0x80
 	// Apply the permutation
 	d.permute()
 	d.state = spongeSqueezing
-	d.n = d.rate
-	copyOut(d, d.storage[:d.rate])
 }
 
 // Write absorbs more data into the hash's state. It panics if any
 // output has already been read.
-func (d *state) Write(p []byte) (written int, err error) {
+func (d *state) Write(p []byte) (n int, err error) {
 	if d.state != spongeAbsorbing {
 		panic("sha3: Write after Read")
 	}
-	written = len(p)
+
+	n = len(p)
 
 	for len(p) > 0 {
-		if d.n == 0 && len(p) >= d.rate {
-			// The fast path; absorb a full "rate" bytes of input and apply the permutation.
-			xorIn(d, p[:d.rate])
-			p = p[d.rate:]
-			keccakF1600(&d.a)
-		} else {
-			// The slow path; buffer the input until we can fill the sponge, and then xor it in.
-			todo := d.rate - d.n
-			if todo > len(p) {
-				todo = len(p)
-			}
-			d.n += copy(d.storage[d.n:], p[:todo])
-			p = p[todo:]
+		x := subtle.XORBytes(d.a[d.n:d.rate], d.a[d.n:d.rate], p)
+		d.n += x
+		p = p[x:]
 
-			// If the sponge is full, apply the permutation.
-			if d.n == d.rate {
-				d.permute()
-			}
+		// If the sponge is full, apply the permutation.
+		if d.n == d.rate {
+			d.permute()
 		}
 	}
 
@@ -156,12 +143,12 @@ func (d *state) Read(out []byte) (n int, err error) {
 
 	// Now, do the squeezing.
 	for len(out) > 0 {
-		n := copy(out, d.storage[d.i:d.n])
-		d.i += n
-		out = out[n:]
+		x := copy(out, d.a[d.n:d.rate])
+		d.n += x
+		out = out[x:]
 
 		// Apply the permutation if we've squeezed the sponge dry.
-		if d.i == d.rate {
+		if d.n == d.rate {
 			d.permute()
 		}
 	}
diff --git a/sha3/xor.go b/sha3/xor.go
deleted file mode 100644
index 6ada5c9..0000000
--- a/sha3/xor.go
+++ /dev/null
@@ -1,40 +0,0 @@
-// Copyright 2015 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package sha3
-
-import (
-	"crypto/subtle"
-	"encoding/binary"
-	"unsafe"
-
-	"golang.org/x/sys/cpu"
-)
-
-// xorIn xors the bytes in buf into the state.
-func xorIn(d *state, buf []byte) {
-	if cpu.IsBigEndian {
-		for i := 0; len(buf) >= 8; i++ {
-			a := binary.LittleEndian.Uint64(buf)
-			d.a[i] ^= a
-			buf = buf[8:]
-		}
-	} else {
-		ab := (*[25 * 64 / 8]byte)(unsafe.Pointer(&d.a))
-		subtle.XORBytes(ab[:], ab[:], buf)
-	}
-}
-
-// copyOut copies uint64s to a byte buffer.
-func copyOut(d *state, b []byte) {
-	if cpu.IsBigEndian {
-		for i := 0; len(b) >= 8; i++ {
-			binary.LittleEndian.PutUint64(b, d.a[i])
-			b = b[8:]
-		}
-	} else {
-		ab := (*[25 * 64 / 8]byte)(unsafe.Pointer(&d.a))
-		copy(b, ab[:])
-	}
-}