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diff --git a/src/crypto/cipher/example_test.go b/src/crypto/cipher/example_test.go
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+++ b/src/crypto/cipher/example_test.go
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+// Copyright 2012 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 cipher_test
+
+import (
+	"bytes"
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/rand"
+	"encoding/hex"
+	"fmt"
+	"io"
+	"os"
+)
+
+func ExampleNewGCM_encrypt() {
+	// Load your secret key from a safe place and reuse it across multiple
+	// Seal/Open calls. (Obviously don't use this example key for anything
+	// real.) If you want to convert a passphrase to a key, use a suitable
+	// package like bcrypt or scrypt.
+	// When decoded the key should be 16 bytes (AES-128) or 32 (AES-256).
+	key, _ := hex.DecodeString("6368616e676520746869732070617373776f726420746f206120736563726574")
+	plaintext := []byte("exampleplaintext")
+
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		panic(err.Error())
+	}
+
+	// Never use more than 2^32 random nonces with a given key because of the risk of a repeat.
+	nonce := make([]byte, 12)
+	if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
+		panic(err.Error())
+	}
+
+	aesgcm, err := cipher.NewGCM(block)
+	if err != nil {
+		panic(err.Error())
+	}
+
+	ciphertext := aesgcm.Seal(nil, nonce, plaintext, nil)
+	fmt.Printf("%x\n", ciphertext)
+}
+
+func ExampleNewGCM_decrypt() {
+	// Load your secret key from a safe place and reuse it across multiple
+	// Seal/Open calls. (Obviously don't use this example key for anything
+	// real.) If you want to convert a passphrase to a key, use a suitable
+	// package like bcrypt or scrypt.
+	// When decoded the key should be 16 bytes (AES-128) or 32 (AES-256).
+	key, _ := hex.DecodeString("6368616e676520746869732070617373776f726420746f206120736563726574")
+	ciphertext, _ := hex.DecodeString("c3aaa29f002ca75870806e44086700f62ce4d43e902b3888e23ceff797a7a471")
+	nonce, _ := hex.DecodeString("64a9433eae7ccceee2fc0eda")
+
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		panic(err.Error())
+	}
+
+	aesgcm, err := cipher.NewGCM(block)
+	if err != nil {
+		panic(err.Error())
+	}
+
+	plaintext, err := aesgcm.Open(nil, nonce, ciphertext, nil)
+	if err != nil {
+		panic(err.Error())
+	}
+
+	fmt.Printf("%s\n", plaintext)
+	// Output: exampleplaintext
+}
+
+func ExampleNewCBCDecrypter() {
+	// Load your secret key from a safe place and reuse it across multiple
+	// NewCipher calls. (Obviously don't use this example key for anything
+	// real.) If you want to convert a passphrase to a key, use a suitable
+	// package like bcrypt or scrypt.
+	key, _ := hex.DecodeString("6368616e676520746869732070617373")
+	ciphertext, _ := hex.DecodeString("73c86d43a9d700a253a96c85b0f6b03ac9792e0e757f869cca306bd3cba1c62b")
+
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		panic(err)
+	}
+
+	// The IV needs to be unique, but not secure. Therefore it's common to
+	// include it at the beginning of the ciphertext.
+	if len(ciphertext) < aes.BlockSize {
+		panic("ciphertext too short")
+	}
+	iv := ciphertext[:aes.BlockSize]
+	ciphertext = ciphertext[aes.BlockSize:]
+
+	// CBC mode always works in whole blocks.
+	if len(ciphertext)%aes.BlockSize != 0 {
+		panic("ciphertext is not a multiple of the block size")
+	}
+
+	mode := cipher.NewCBCDecrypter(block, iv)
+
+	// CryptBlocks can work in-place if the two arguments are the same.
+	mode.CryptBlocks(ciphertext, ciphertext)
+
+	// If the original plaintext lengths are not a multiple of the block
+	// size, padding would have to be added when encrypting, which would be
+	// removed at this point. For an example, see
+	// https://tools.ietf.org/html/rfc5246#section-6.2.3.2. However, it's
+	// critical to note that ciphertexts must be authenticated (i.e. by
+	// using crypto/hmac) before being decrypted in order to avoid creating
+	// a padding oracle.
+
+	fmt.Printf("%s\n", ciphertext)
+	// Output: exampleplaintext
+}
+
+func ExampleNewCBCEncrypter() {
+	// Load your secret key from a safe place and reuse it across multiple
+	// NewCipher calls. (Obviously don't use this example key for anything
+	// real.) If you want to convert a passphrase to a key, use a suitable
+	// package like bcrypt or scrypt.
+	key, _ := hex.DecodeString("6368616e676520746869732070617373")
+	plaintext := []byte("exampleplaintext")
+
+	// CBC mode works on blocks so plaintexts may need to be padded to the
+	// next whole block. For an example of such padding, see
+	// https://tools.ietf.org/html/rfc5246#section-6.2.3.2. Here we'll
+	// assume that the plaintext is already of the correct length.
+	if len(plaintext)%aes.BlockSize != 0 {
+		panic("plaintext is not a multiple of the block size")
+	}
+
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		panic(err)
+	}
+
+	// The IV needs to be unique, but not secure. Therefore it's common to
+	// include it at the beginning of the ciphertext.
+	ciphertext := make([]byte, aes.BlockSize+len(plaintext))
+	iv := ciphertext[:aes.BlockSize]
+	if _, err := io.ReadFull(rand.Reader, iv); err != nil {
+		panic(err)
+	}
+
+	mode := cipher.NewCBCEncrypter(block, iv)
+	mode.CryptBlocks(ciphertext[aes.BlockSize:], plaintext)
+
+	// It's important to remember that ciphertexts must be authenticated
+	// (i.e. by using crypto/hmac) as well as being encrypted in order to
+	// be secure.
+
+	fmt.Printf("%x\n", ciphertext)
+}
+
+func ExampleNewCFBDecrypter() {
+	// Load your secret key from a safe place and reuse it across multiple
+	// NewCipher calls. (Obviously don't use this example key for anything
+	// real.) If you want to convert a passphrase to a key, use a suitable
+	// package like bcrypt or scrypt.
+	key, _ := hex.DecodeString("6368616e676520746869732070617373")
+	ciphertext, _ := hex.DecodeString("7dd015f06bec7f1b8f6559dad89f4131da62261786845100056b353194ad")
+
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		panic(err)
+	}
+
+	// The IV needs to be unique, but not secure. Therefore it's common to
+	// include it at the beginning of the ciphertext.
+	if len(ciphertext) < aes.BlockSize {
+		panic("ciphertext too short")
+	}
+	iv := ciphertext[:aes.BlockSize]
+	ciphertext = ciphertext[aes.BlockSize:]
+
+	stream := cipher.NewCFBDecrypter(block, iv)
+
+	// XORKeyStream can work in-place if the two arguments are the same.
+	stream.XORKeyStream(ciphertext, ciphertext)
+	fmt.Printf("%s", ciphertext)
+	// Output: some plaintext
+}
+
+func ExampleNewCFBEncrypter() {
+	// Load your secret key from a safe place and reuse it across multiple
+	// NewCipher calls. (Obviously don't use this example key for anything
+	// real.) If you want to convert a passphrase to a key, use a suitable
+	// package like bcrypt or scrypt.
+	key, _ := hex.DecodeString("6368616e676520746869732070617373")
+	plaintext := []byte("some plaintext")
+
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		panic(err)
+	}
+
+	// The IV needs to be unique, but not secure. Therefore it's common to
+	// include it at the beginning of the ciphertext.
+	ciphertext := make([]byte, aes.BlockSize+len(plaintext))
+	iv := ciphertext[:aes.BlockSize]
+	if _, err := io.ReadFull(rand.Reader, iv); err != nil {
+		panic(err)
+	}
+
+	stream := cipher.NewCFBEncrypter(block, iv)
+	stream.XORKeyStream(ciphertext[aes.BlockSize:], plaintext)
+
+	// It's important to remember that ciphertexts must be authenticated
+	// (i.e. by using crypto/hmac) as well as being encrypted in order to
+	// be secure.
+	fmt.Printf("%x\n", ciphertext)
+}
+
+func ExampleNewCTR() {
+	// Load your secret key from a safe place and reuse it across multiple
+	// NewCipher calls. (Obviously don't use this example key for anything
+	// real.) If you want to convert a passphrase to a key, use a suitable
+	// package like bcrypt or scrypt.
+	key, _ := hex.DecodeString("6368616e676520746869732070617373")
+	plaintext := []byte("some plaintext")
+
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		panic(err)
+	}
+
+	// The IV needs to be unique, but not secure. Therefore it's common to
+	// include it at the beginning of the ciphertext.
+	ciphertext := make([]byte, aes.BlockSize+len(plaintext))
+	iv := ciphertext[:aes.BlockSize]
+	if _, err := io.ReadFull(rand.Reader, iv); err != nil {
+		panic(err)
+	}
+
+	stream := cipher.NewCTR(block, iv)
+	stream.XORKeyStream(ciphertext[aes.BlockSize:], plaintext)
+
+	// It's important to remember that ciphertexts must be authenticated
+	// (i.e. by using crypto/hmac) as well as being encrypted in order to
+	// be secure.
+
+	// CTR mode is the same for both encryption and decryption, so we can
+	// also decrypt that ciphertext with NewCTR.
+
+	plaintext2 := make([]byte, len(plaintext))
+	stream = cipher.NewCTR(block, iv)
+	stream.XORKeyStream(plaintext2, ciphertext[aes.BlockSize:])
+
+	fmt.Printf("%s\n", plaintext2)
+	// Output: some plaintext
+}
+
+func ExampleNewOFB() {
+	// Load your secret key from a safe place and reuse it across multiple
+	// NewCipher calls. (Obviously don't use this example key for anything
+	// real.) If you want to convert a passphrase to a key, use a suitable
+	// package like bcrypt or scrypt.
+	key, _ := hex.DecodeString("6368616e676520746869732070617373")
+	plaintext := []byte("some plaintext")
+
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		panic(err)
+	}
+
+	// The IV needs to be unique, but not secure. Therefore it's common to
+	// include it at the beginning of the ciphertext.
+	ciphertext := make([]byte, aes.BlockSize+len(plaintext))
+	iv := ciphertext[:aes.BlockSize]
+	if _, err := io.ReadFull(rand.Reader, iv); err != nil {
+		panic(err)
+	}
+
+	stream := cipher.NewOFB(block, iv)
+	stream.XORKeyStream(ciphertext[aes.BlockSize:], plaintext)
+
+	// It's important to remember that ciphertexts must be authenticated
+	// (i.e. by using crypto/hmac) as well as being encrypted in order to
+	// be secure.
+
+	// OFB mode is the same for both encryption and decryption, so we can
+	// also decrypt that ciphertext with NewOFB.
+
+	plaintext2 := make([]byte, len(plaintext))
+	stream = cipher.NewOFB(block, iv)
+	stream.XORKeyStream(plaintext2, ciphertext[aes.BlockSize:])
+
+	fmt.Printf("%s\n", plaintext2)
+	// Output: some plaintext
+}
+
+func ExampleStreamReader() {
+	// Load your secret key from a safe place and reuse it across multiple
+	// NewCipher calls. (Obviously don't use this example key for anything
+	// real.) If you want to convert a passphrase to a key, use a suitable
+	// package like bcrypt or scrypt.
+	key, _ := hex.DecodeString("6368616e676520746869732070617373")
+
+	encrypted, _ := hex.DecodeString("cf0495cc6f75dafc23948538e79904a9")
+	bReader := bytes.NewReader(encrypted)
+
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		panic(err)
+	}
+
+	// If the key is unique for each ciphertext, then it's ok to use a zero
+	// IV.
+	var iv [aes.BlockSize]byte
+	stream := cipher.NewOFB(block, iv[:])
+
+	reader := &cipher.StreamReader{S: stream, R: bReader}
+	// Copy the input to the output stream, decrypting as we go.
+	if _, err := io.Copy(os.Stdout, reader); err != nil {
+		panic(err)
+	}
+
+	// Note that this example is simplistic in that it omits any
+	// authentication of the encrypted data. If you were actually to use
+	// StreamReader in this manner, an attacker could flip arbitrary bits in
+	// the output.
+
+	// Output: some secret text
+}
+
+func ExampleStreamWriter() {
+	// Load your secret key from a safe place and reuse it across multiple
+	// NewCipher calls. (Obviously don't use this example key for anything
+	// real.) If you want to convert a passphrase to a key, use a suitable
+	// package like bcrypt or scrypt.
+	key, _ := hex.DecodeString("6368616e676520746869732070617373")
+
+	bReader := bytes.NewReader([]byte("some secret text"))
+
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		panic(err)
+	}
+
+	// If the key is unique for each ciphertext, then it's ok to use a zero
+	// IV.
+	var iv [aes.BlockSize]byte
+	stream := cipher.NewOFB(block, iv[:])
+
+	var out bytes.Buffer
+
+	writer := &cipher.StreamWriter{S: stream, W: &out}
+	// Copy the input to the output buffer, encrypting as we go.
+	if _, err := io.Copy(writer, bReader); err != nil {
+		panic(err)
+	}
+
+	// Note that this example is simplistic in that it omits any
+	// authentication of the encrypted data. If you were actually to use
+	// StreamReader in this manner, an attacker could flip arbitrary bits in
+	// the decrypted result.
+
+	fmt.Printf("%x\n", out.Bytes())
+	// Output: cf0495cc6f75dafc23948538e79904a9
+}