Godeps, vendor: convert dependency management to trash (#3198)

This commit converts the dependency management from Godeps to the vendor
folder, also switching the tool from godep to trash. Since the upstream tool
lacks a few features proposed via a few PRs, until those PRs are merged in
(if), use github.com/karalabe/trash.

You can update dependencies via trash --update.

All dependencies have been updated to their latest version.

Parts of the build system are reworked to drop old notions of Godeps and
invocation of the go vet command so that it doesn't run against the vendor
folder, as that will just blow up during vetting.

The conversion drops OpenCL (and hence GPU mining support) from ethash and our
codebase. The short reasoning is that there's noone to maintain and having
opencl libs in our deps messes up builds as go install ./... tries to build
them, failing with unsatisfied link errors for the C OpenCL deps.

golang.org/x/net/context is not vendored in. We expect it to be fetched by the
user (i.e. using go get). To keep ci.go builds reproducible the package is
"vendored" in build/_vendor.

vendor/golang.org/x/crypto/.gitattributes

@@ -0,0 +1,10 @@
+# Treat all files in this repo as binary, with no git magic updating
+# line endings. Windows users contributing to Go will need to use a
+# modern version of git and editors capable of LF line endings.
+#
+# We'll prevent accidental CRLF line endings from entering the repo
+# via the git-review gofmt checks.
+#
+# See golang.org/issue/9281
+
+* -text

vendor/golang.org/x/crypto/.gitignore

@@ -0,0 +1,2 @@
+# Add no patterns to .hgignore except for files generated by the build.
+last-change

vendor/golang.org/x/crypto/AUTHORS

@@ -0,0 +1,3 @@
+# This source code refers to The Go Authors for copyright purposes.
+# The master list of authors is in the main Go distribution,
+# visible at http://tip.golang.org/AUTHORS.

vendor/golang.org/x/crypto/CONTRIBUTING.md

@@ -0,0 +1,31 @@
+# Contributing to Go
+
+Go is an open source project.
+
+It is the work of hundreds of contributors. We appreciate your help!
+
+
+## Filing issues
+
+When [filing an issue](https://golang.org/issue/new), make sure to answer these five questions:
+
+1. What version of Go are you using (`go version`)?
+2. What operating system and processor architecture are you using?
+3. What did you do?
+4. What did you expect to see?
+5. What did you see instead?
+
+General questions should go to the [golang-nuts mailing list](https://groups.google.com/group/golang-nuts) instead of the issue tracker.
+The gophers there will answer or ask you to file an issue if you've tripped over a bug.
+
+## Contributing code
+
+Please read the [Contribution Guidelines](https://golang.org/doc/contribute.html)
+before sending patches.
+
+**We do not accept GitHub pull requests**
+(we use [Gerrit](https://code.google.com/p/gerrit/) instead for code review).
+
+Unless otherwise noted, the Go source files are distributed under
+the BSD-style license found in the LICENSE file.
+

vendor/golang.org/x/crypto/CONTRIBUTORS

@@ -0,0 +1,3 @@
+# This source code was written by the Go contributors.
+# The master list of contributors is in the main Go distribution,
+# visible at http://tip.golang.org/CONTRIBUTORS.

vendor/golang.org/x/crypto/LICENSE

@@ -0,0 +1,27 @@
+Copyright (c) 2009 The Go Authors. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+   * Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+   * Redistributions in binary form must reproduce the above
+copyright notice, this list of conditions and the following disclaimer
+in the documentation and/or other materials provided with the
+distribution.
+   * Neither the name of Google Inc. nor the names of its
+contributors may be used to endorse or promote products derived from
+this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

vendor/golang.org/x/crypto/PATENTS

@@ -0,0 +1,22 @@
+Additional IP Rights Grant (Patents)
+
+"This implementation" means the copyrightable works distributed by
+Google as part of the Go project.
+
+Google hereby grants to You a perpetual, worldwide, non-exclusive,
+no-charge, royalty-free, irrevocable (except as stated in this section)
+patent license to make, have made, use, offer to sell, sell, import,
+transfer and otherwise run, modify and propagate the contents of this
+implementation of Go, where such license applies only to those patent
+claims, both currently owned or controlled by Google and acquired in
+the future, licensable by Google that are necessarily infringed by this
+implementation of Go.  This grant does not include claims that would be
+infringed only as a consequence of further modification of this
+implementation.  If you or your agent or exclusive licensee institute or
+order or agree to the institution of patent litigation against any
+entity (including a cross-claim or counterclaim in a lawsuit) alleging
+that this implementation of Go or any code incorporated within this
+implementation of Go constitutes direct or contributory patent
+infringement, or inducement of patent infringement, then any patent
+rights granted to you under this License for this implementation of Go
+shall terminate as of the date such litigation is filed.

vendor/golang.org/x/crypto/README

@@ -0,0 +1,3 @@
+This repository holds supplementary Go cryptography libraries.
+
+To submit changes to this repository, see http://golang.org/doc/contribute.html.

vendor/golang.org/x/crypto/codereview.cfg

@@ -0,0 +1 @@
+issuerepo: golang/go

vendor/golang.org/x/crypto/pbkdf2/pbkdf2.go

@@ -0,0 +1,77 @@
+// 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 pbkdf2 implements the key derivation function PBKDF2 as defined in RFC
+2898 / PKCS #5 v2.0.
+
+A key derivation function is useful when encrypting data based on a password
+or any other not-fully-random data. It uses a pseudorandom function to derive
+a secure encryption key based on the password.
+
+While v2.0 of the standard defines only one pseudorandom function to use,
+HMAC-SHA1, the drafted v2.1 specification allows use of all five FIPS Approved
+Hash Functions SHA-1, SHA-224, SHA-256, SHA-384 and SHA-512 for HMAC. To
+choose, you can pass the `New` functions from the different SHA packages to
+pbkdf2.Key.
+*/
+package pbkdf2 // import "golang.org/x/crypto/pbkdf2"
+
+import (
+	"crypto/hmac"
+	"hash"
+)
+
+// Key derives a key from the password, salt and iteration count, returning a
+// []byte of length keylen that can be used as cryptographic key. The key is
+// derived based on the method described as PBKDF2 with the HMAC variant using
+// the supplied hash function.
+//
+// For example, to use a HMAC-SHA-1 based PBKDF2 key derivation function, you
+// can get a derived key for e.g. AES-256 (which needs a 32-byte key) by
+// doing:
+//
+// 	dk := pbkdf2.Key([]byte("some password"), salt, 4096, 32, sha1.New)
+//
+// Remember to get a good random salt. At least 8 bytes is recommended by the
+// RFC.
+//
+// Using a higher iteration count will increase the cost of an exhaustive
+// search but will also make derivation proportionally slower.
+func Key(password, salt []byte, iter, keyLen int, h func() hash.Hash) []byte {
+	prf := hmac.New(h, password)
+	hashLen := prf.Size()
+	numBlocks := (keyLen + hashLen - 1) / hashLen
+
+	var buf [4]byte
+	dk := make([]byte, 0, numBlocks*hashLen)
+	U := make([]byte, hashLen)
+	for block := 1; block <= numBlocks; block++ {
+		// N.B.: || means concatenation, ^ means XOR
+		// for each block T_i = U_1 ^ U_2 ^ ... ^ U_iter
+		// U_1 = PRF(password, salt || uint(i))
+		prf.Reset()
+		prf.Write(salt)
+		buf[0] = byte(block >> 24)
+		buf[1] = byte(block >> 16)
+		buf[2] = byte(block >> 8)
+		buf[3] = byte(block)
+		prf.Write(buf[:4])
+		dk = prf.Sum(dk)
+		T := dk[len(dk)-hashLen:]
+		copy(U, T)
+
+		// U_n = PRF(password, U_(n-1))
+		for n := 2; n <= iter; n++ {
+			prf.Reset()
+			prf.Write(U)
+			U = U[:0]
+			U = prf.Sum(U)
+			for x := range U {
+				T[x] ^= U[x]
+			}
+		}
+	}
+	return dk[:keyLen]
+}

vendor/golang.org/x/crypto/ripemd160/ripemd160.go

@@ -0,0 +1,120 @@
+// Copyright 2010 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 ripemd160 implements the RIPEMD-160 hash algorithm.
+package ripemd160 // import "golang.org/x/crypto/ripemd160"
+
+// RIPEMD-160 is designed by by Hans Dobbertin, Antoon Bosselaers, and Bart
+// Preneel with specifications available at:
+// http://homes.esat.kuleuven.be/~cosicart/pdf/AB-9601/AB-9601.pdf.
+
+import (
+	"crypto"
+	"hash"
+)
+
+func init() {
+	crypto.RegisterHash(crypto.RIPEMD160, New)
+}
+
+// The size of the checksum in bytes.
+const Size = 20
+
+// The block size of the hash algorithm in bytes.
+const BlockSize = 64
+
+const (
+	_s0 = 0x67452301
+	_s1 = 0xefcdab89
+	_s2 = 0x98badcfe
+	_s3 = 0x10325476
+	_s4 = 0xc3d2e1f0
+)
+
+// digest represents the partial evaluation of a checksum.
+type digest struct {
+	s  [5]uint32       // running context
+	x  [BlockSize]byte // temporary buffer
+	nx int             // index into x
+	tc uint64          // total count of bytes processed
+}
+
+func (d *digest) Reset() {
+	d.s[0], d.s[1], d.s[2], d.s[3], d.s[4] = _s0, _s1, _s2, _s3, _s4
+	d.nx = 0
+	d.tc = 0
+}
+
+// New returns a new hash.Hash computing the checksum.
+func New() hash.Hash {
+	result := new(digest)
+	result.Reset()
+	return result
+}
+
+func (d *digest) Size() int { return Size }
+
+func (d *digest) BlockSize() int { return BlockSize }
+
+func (d *digest) Write(p []byte) (nn int, err error) {
+	nn = len(p)
+	d.tc += uint64(nn)
+	if d.nx > 0 {
+		n := len(p)
+		if n > BlockSize-d.nx {
+			n = BlockSize - d.nx
+		}
+		for i := 0; i < n; i++ {
+			d.x[d.nx+i] = p[i]
+		}
+		d.nx += n
+		if d.nx == BlockSize {
+			_Block(d, d.x[0:])
+			d.nx = 0
+		}
+		p = p[n:]
+	}
+	n := _Block(d, p)
+	p = p[n:]
+	if len(p) > 0 {
+		d.nx = copy(d.x[:], p)
+	}
+	return
+}
+
+func (d0 *digest) Sum(in []byte) []byte {
+	// Make a copy of d0 so that caller can keep writing and summing.
+	d := *d0
+
+	// Padding.  Add a 1 bit and 0 bits until 56 bytes mod 64.
+	tc := d.tc
+	var tmp [64]byte
+	tmp[0] = 0x80
+	if tc%64 < 56 {
+		d.Write(tmp[0 : 56-tc%64])
+	} else {
+		d.Write(tmp[0 : 64+56-tc%64])
+	}
+
+	// Length in bits.
+	tc <<= 3
+	for i := uint(0); i < 8; i++ {
+		tmp[i] = byte(tc >> (8 * i))
+	}
+	d.Write(tmp[0:8])
+
+	if d.nx != 0 {
+		panic("d.nx != 0")
+	}
+
+	var digest [Size]byte
+	for i, s := range d.s {
+		digest[i*4] = byte(s)
+		digest[i*4+1] = byte(s >> 8)
+		digest[i*4+2] = byte(s >> 16)
+		digest[i*4+3] = byte(s >> 24)
+	}
+
+	return append(in, digest[:]...)
+}

vendor/golang.org/x/crypto/ripemd160/ripemd160block.go

@@ -0,0 +1,161 @@
+// Copyright 2010 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.
+
+// RIPEMD-160 block step.
+// In its own file so that a faster assembly or C version
+// can be substituted easily.
+
+package ripemd160
+
+// work buffer indices and roll amounts for one line
+var _n = [80]uint{
+	0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,
+	7, 4, 13, 1, 10, 6, 15, 3, 12, 0, 9, 5, 2, 14, 11, 8,
+	3, 10, 14, 4, 9, 15, 8, 1, 2, 7, 0, 6, 13, 11, 5, 12,
+	1, 9, 11, 10, 0, 8, 12, 4, 13, 3, 7, 15, 14, 5, 6, 2,
+	4, 0, 5, 9, 7, 12, 2, 10, 14, 1, 3, 8, 11, 6, 15, 13,
+}
+
+var _r = [80]uint{
+	11, 14, 15, 12, 5, 8, 7, 9, 11, 13, 14, 15, 6, 7, 9, 8,
+	7, 6, 8, 13, 11, 9, 7, 15, 7, 12, 15, 9, 11, 7, 13, 12,
+	11, 13, 6, 7, 14, 9, 13, 15, 14, 8, 13, 6, 5, 12, 7, 5,
+	11, 12, 14, 15, 14, 15, 9, 8, 9, 14, 5, 6, 8, 6, 5, 12,
+	9, 15, 5, 11, 6, 8, 13, 12, 5, 12, 13, 14, 11, 8, 5, 6,
+}
+
+// same for the other parallel one
+var n_ = [80]uint{
+	5, 14, 7, 0, 9, 2, 11, 4, 13, 6, 15, 8, 1, 10, 3, 12,
+	6, 11, 3, 7, 0, 13, 5, 10, 14, 15, 8, 12, 4, 9, 1, 2,
+	15, 5, 1, 3, 7, 14, 6, 9, 11, 8, 12, 2, 10, 0, 4, 13,
+	8, 6, 4, 1, 3, 11, 15, 0, 5, 12, 2, 13, 9, 7, 10, 14,
+	12, 15, 10, 4, 1, 5, 8, 7, 6, 2, 13, 14, 0, 3, 9, 11,
+}
+
+var r_ = [80]uint{
+	8, 9, 9, 11, 13, 15, 15, 5, 7, 7, 8, 11, 14, 14, 12, 6,
+	9, 13, 15, 7, 12, 8, 9, 11, 7, 7, 12, 7, 6, 15, 13, 11,
+	9, 7, 15, 11, 8, 6, 6, 14, 12, 13, 5, 14, 13, 13, 7, 5,
+	15, 5, 8, 11, 14, 14, 6, 14, 6, 9, 12, 9, 12, 5, 15, 8,
+	8, 5, 12, 9, 12, 5, 14, 6, 8, 13, 6, 5, 15, 13, 11, 11,
+}
+
+func _Block(md *digest, p []byte) int {
+	n := 0
+	var x [16]uint32
+	var alpha, beta uint32
+	for len(p) >= BlockSize {
+		a, b, c, d, e := md.s[0], md.s[1], md.s[2], md.s[3], md.s[4]
+		aa, bb, cc, dd, ee := a, b, c, d, e
+		j := 0
+		for i := 0; i < 16; i++ {
+			x[i] = uint32(p[j]) | uint32(p[j+1])<<8 | uint32(p[j+2])<<16 | uint32(p[j+3])<<24
+			j += 4
+		}
+
+		// round 1
+		i := 0
+		for i < 16 {
+			alpha = a + (b ^ c ^ d) + x[_n[i]]
+			s := _r[i]
+			alpha = (alpha<<s | alpha>>(32-s)) + e
+			beta = c<<10 | c>>22
+			a, b, c, d, e = e, alpha, b, beta, d
+
+			// parallel line
+			alpha = aa + (bb ^ (cc | ^dd)) + x[n_[i]] + 0x50a28be6
+			s = r_[i]
+			alpha = (alpha<<s | alpha>>(32-s)) + ee
+			beta = cc<<10 | cc>>22
+			aa, bb, cc, dd, ee = ee, alpha, bb, beta, dd
+
+			i++
+		}
+
+		// round 2
+		for i < 32 {
+			alpha = a + (b&c | ^b&d) + x[_n[i]] + 0x5a827999
+			s := _r[i]
+			alpha = (alpha<<s | alpha>>(32-s)) + e
+			beta = c<<10 | c>>22
+			a, b, c, d, e = e, alpha, b, beta, d
+
+			// parallel line
+			alpha = aa + (bb&dd | cc&^dd) + x[n_[i]] + 0x5c4dd124
+			s = r_[i]
+			alpha = (alpha<<s | alpha>>(32-s)) + ee
+			beta = cc<<10 | cc>>22
+			aa, bb, cc, dd, ee = ee, alpha, bb, beta, dd
+
+			i++
+		}
+
+		// round 3
+		for i < 48 {
+			alpha = a + (b | ^c ^ d) + x[_n[i]] + 0x6ed9eba1
+			s := _r[i]
+			alpha = (alpha<<s | alpha>>(32-s)) + e
+			beta = c<<10 | c>>22
+			a, b, c, d, e = e, alpha, b, beta, d
+
+			// parallel line
+			alpha = aa + (bb | ^cc ^ dd) + x[n_[i]] + 0x6d703ef3
+			s = r_[i]
+			alpha = (alpha<<s | alpha>>(32-s)) + ee
+			beta = cc<<10 | cc>>22
+			aa, bb, cc, dd, ee = ee, alpha, bb, beta, dd
+
+			i++
+		}
+
+		// round 4
+		for i < 64 {
+			alpha = a + (b&d | c&^d) + x[_n[i]] + 0x8f1bbcdc
+			s := _r[i]
+			alpha = (alpha<<s | alpha>>(32-s)) + e
+			beta = c<<10 | c>>22
+			a, b, c, d, e = e, alpha, b, beta, d
+
+			// parallel line
+			alpha = aa + (bb&cc | ^bb&dd) + x[n_[i]] + 0x7a6d76e9
+			s = r_[i]
+			alpha = (alpha<<s | alpha>>(32-s)) + ee
+			beta = cc<<10 | cc>>22
+			aa, bb, cc, dd, ee = ee, alpha, bb, beta, dd
+
+			i++
+		}
+
+		// round 5
+		for i < 80 {
+			alpha = a + (b ^ (c | ^d)) + x[_n[i]] + 0xa953fd4e
+			s := _r[i]
+			alpha = (alpha<<s | alpha>>(32-s)) + e
+			beta = c<<10 | c>>22
+			a, b, c, d, e = e, alpha, b, beta, d
+
+			// parallel line
+			alpha = aa + (bb ^ cc ^ dd) + x[n_[i]]
+			s = r_[i]
+			alpha = (alpha<<s | alpha>>(32-s)) + ee
+			beta = cc<<10 | cc>>22
+			aa, bb, cc, dd, ee = ee, alpha, bb, beta, dd
+
+			i++
+		}
+
+		// combine results
+		dd += c + md.s[1]
+		md.s[1] = md.s[2] + d + ee
+		md.s[2] = md.s[3] + e + aa
+		md.s[3] = md.s[4] + a + bb
+		md.s[4] = md.s[0] + b + cc
+		md.s[0] = dd
+
+		p = p[BlockSize:]
+		n += BlockSize
+	}
+	return n
+}

vendor/golang.org/x/crypto/scrypt/scrypt.go

@@ -0,0 +1,243 @@
+// 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 scrypt implements the scrypt key derivation function as defined in
+// Colin Percival's paper "Stronger Key Derivation via Sequential Memory-Hard
+// Functions" (http://www.tarsnap.com/scrypt/scrypt.pdf).
+package scrypt // import "golang.org/x/crypto/scrypt"
+
+import (
+	"crypto/sha256"
+	"errors"
+
+	"golang.org/x/crypto/pbkdf2"
+)
+
+const maxInt = int(^uint(0) >> 1)
+
+// blockCopy copies n numbers from src into dst.
+func blockCopy(dst, src []uint32, n int) {
+	copy(dst, src[:n])
+}
+
+// blockXOR XORs numbers from dst with n numbers from src.
+func blockXOR(dst, src []uint32, n int) {
+	for i, v := range src[:n] {
+		dst[i] ^= v
+	}
+}
+
+// salsaXOR applies Salsa20/8 to the XOR of 16 numbers from tmp and in,
+// and puts the result into both both tmp and out.
+func salsaXOR(tmp *[16]uint32, in, out []uint32) {
+	w0 := tmp[0] ^ in[0]
+	w1 := tmp[1] ^ in[1]
+	w2 := tmp[2] ^ in[2]
+	w3 := tmp[3] ^ in[3]
+	w4 := tmp[4] ^ in[4]
+	w5 := tmp[5] ^ in[5]
+	w6 := tmp[6] ^ in[6]
+	w7 := tmp[7] ^ in[7]
+	w8 := tmp[8] ^ in[8]
+	w9 := tmp[9] ^ in[9]
+	w10 := tmp[10] ^ in[10]
+	w11 := tmp[11] ^ in[11]
+	w12 := tmp[12] ^ in[12]
+	w13 := tmp[13] ^ in[13]
+	w14 := tmp[14] ^ in[14]
+	w15 := tmp[15] ^ in[15]
+
+	x0, x1, x2, x3, x4, x5, x6, x7, x8 := w0, w1, w2, w3, w4, w5, w6, w7, w8
+	x9, x10, x11, x12, x13, x14, x15 := w9, w10, w11, w12, w13, w14, w15
+
+	for i := 0; i < 8; i += 2 {
+		u := x0 + x12
+		x4 ^= u<<7 | u>>(32-7)
+		u = x4 + x0
+		x8 ^= u<<9 | u>>(32-9)
+		u = x8 + x4
+		x12 ^= u<<13 | u>>(32-13)
+		u = x12 + x8
+		x0 ^= u<<18 | u>>(32-18)
+
+		u = x5 + x1
+		x9 ^= u<<7 | u>>(32-7)
+		u = x9 + x5
+		x13 ^= u<<9 | u>>(32-9)
+		u = x13 + x9
+		x1 ^= u<<13 | u>>(32-13)
+		u = x1 + x13
+		x5 ^= u<<18 | u>>(32-18)
+
+		u = x10 + x6
+		x14 ^= u<<7 | u>>(32-7)
+		u = x14 + x10
+		x2 ^= u<<9 | u>>(32-9)
+		u = x2 + x14
+		x6 ^= u<<13 | u>>(32-13)
+		u = x6 + x2
+		x10 ^= u<<18 | u>>(32-18)
+
+		u = x15 + x11
+		x3 ^= u<<7 | u>>(32-7)
+		u = x3 + x15
+		x7 ^= u<<9 | u>>(32-9)
+		u = x7 + x3
+		x11 ^= u<<13 | u>>(32-13)
+		u = x11 + x7
+		x15 ^= u<<18 | u>>(32-18)
+
+		u = x0 + x3
+		x1 ^= u<<7 | u>>(32-7)
+		u = x1 + x0
+		x2 ^= u<<9 | u>>(32-9)
+		u = x2 + x1
+		x3 ^= u<<13 | u>>(32-13)
+		u = x3 + x2
+		x0 ^= u<<18 | u>>(32-18)
+
+		u = x5 + x4
+		x6 ^= u<<7 | u>>(32-7)
+		u = x6 + x5
+		x7 ^= u<<9 | u>>(32-9)
+		u = x7 + x6
+		x4 ^= u<<13 | u>>(32-13)
+		u = x4 + x7
+		x5 ^= u<<18 | u>>(32-18)
+
+		u = x10 + x9
+		x11 ^= u<<7 | u>>(32-7)
+		u = x11 + x10
+		x8 ^= u<<9 | u>>(32-9)
+		u = x8 + x11
+		x9 ^= u<<13 | u>>(32-13)
+		u = x9 + x8
+		x10 ^= u<<18 | u>>(32-18)
+
+		u = x15 + x14
+		x12 ^= u<<7 | u>>(32-7)
+		u = x12 + x15
+		x13 ^= u<<9 | u>>(32-9)
+		u = x13 + x12
+		x14 ^= u<<13 | u>>(32-13)
+		u = x14 + x13
+		x15 ^= u<<18 | u>>(32-18)
+	}
+	x0 += w0
+	x1 += w1
+	x2 += w2
+	x3 += w3
+	x4 += w4
+	x5 += w5
+	x6 += w6
+	x7 += w7
+	x8 += w8
+	x9 += w9
+	x10 += w10
+	x11 += w11
+	x12 += w12
+	x13 += w13
+	x14 += w14
+	x15 += w15
+
+	out[0], tmp[0] = x0, x0
+	out[1], tmp[1] = x1, x1
+	out[2], tmp[2] = x2, x2
+	out[3], tmp[3] = x3, x3
+	out[4], tmp[4] = x4, x4
+	out[5], tmp[5] = x5, x5
+	out[6], tmp[6] = x6, x6
+	out[7], tmp[7] = x7, x7
+	out[8], tmp[8] = x8, x8
+	out[9], tmp[9] = x9, x9
+	out[10], tmp[10] = x10, x10
+	out[11], tmp[11] = x11, x11
+	out[12], tmp[12] = x12, x12
+	out[13], tmp[13] = x13, x13
+	out[14], tmp[14] = x14, x14
+	out[15], tmp[15] = x15, x15
+}
+
+func blockMix(tmp *[16]uint32, in, out []uint32, r int) {
+	blockCopy(tmp[:], in[(2*r-1)*16:], 16)
+	for i := 0; i < 2*r; i += 2 {
+		salsaXOR(tmp, in[i*16:], out[i*8:])
+		salsaXOR(tmp, in[i*16+16:], out[i*8+r*16:])
+	}
+}
+
+func integer(b []uint32, r int) uint64 {
+	j := (2*r - 1) * 16
+	return uint64(b[j]) | uint64(b[j+1])<<32
+}
+
+func smix(b []byte, r, N int, v, xy []uint32) {
+	var tmp [16]uint32
+	x := xy
+	y := xy[32*r:]
+
+	j := 0
+	for i := 0; i < 32*r; i++ {
+		x[i] = uint32(b[j]) | uint32(b[j+1])<<8 | uint32(b[j+2])<<16 | uint32(b[j+3])<<24
+		j += 4
+	}
+	for i := 0; i < N; i += 2 {
+		blockCopy(v[i*(32*r):], x, 32*r)
+		blockMix(&tmp, x, y, r)
+
+		blockCopy(v[(i+1)*(32*r):], y, 32*r)
+		blockMix(&tmp, y, x, r)
+	}
+	for i := 0; i < N; i += 2 {
+		j := int(integer(x, r) & uint64(N-1))
+		blockXOR(x, v[j*(32*r):], 32*r)
+		blockMix(&tmp, x, y, r)
+
+		j = int(integer(y, r) & uint64(N-1))
+		blockXOR(y, v[j*(32*r):], 32*r)
+		blockMix(&tmp, y, x, r)
+	}
+	j = 0
+	for _, v := range x[:32*r] {
+		b[j+0] = byte(v >> 0)
+		b[j+1] = byte(v >> 8)
+		b[j+2] = byte(v >> 16)
+		b[j+3] = byte(v >> 24)
+		j += 4
+	}
+}
+
+// Key derives a key from the password, salt, and cost parameters, returning
+// a byte slice of length keyLen that can be used as cryptographic key.
+//
+// N is a CPU/memory cost parameter, which must be a power of two greater than 1.
+// r and p must satisfy r * p < 2³⁰. If the parameters do not satisfy the
+// limits, the function returns a nil byte slice and an error.
+//
+// For example, you can get a derived key for e.g. AES-256 (which needs a
+// 32-byte key) by doing:
+//
+//      dk, err := scrypt.Key([]byte("some password"), salt, 16384, 8, 1, 32)
+//
+// The recommended parameters for interactive logins as of 2009 are N=16384,
+// r=8, p=1. They should be increased as memory latency and CPU parallelism
+// increases. Remember to get a good random salt.
+func Key(password, salt []byte, N, r, p, keyLen int) ([]byte, error) {
+	if N <= 1 || N&(N-1) != 0 {
+		return nil, errors.New("scrypt: N must be > 1 and a power of 2")
+	}
+	if uint64(r)*uint64(p) >= 1<<30 || r > maxInt/128/p || r > maxInt/256 || N > maxInt/128/r {
+		return nil, errors.New("scrypt: parameters are too large")
+	}
+
+	xy := make([]uint32, 64*r)
+	v := make([]uint32, 32*N*r)
+	b := pbkdf2.Key(password, salt, 1, p*128*r, sha256.New)
+
+	for i := 0; i < p; i++ {
+		smix(b[i*128*r:], r, N, v, xy)
+	}
+
+	return pbkdf2.Key(password, b, 1, keyLen, sha256.New), nil
+}