"hashlib" --- セキュアハッシュとメッセージダイジェスト
******************************************************

**ソースコード:** Lib/hashlib.py

======================================================================

This module implements a common interface to many different secure
hash and message digest algorithms.  Included are the FIPS secure hash
algorithms SHA1, SHA224, SHA256, SHA384, SHA512, (defined in the FIPS
180-4 standard), the SHA-3 series (defined in the FIPS 202 standard)
as well as RSA's MD5 algorithm (defined in internet **RFC 1321**).
The terms "secure hash" and "message digest" are interchangeable.
Older algorithms were called message digests.  The modern term is
secure hash.

注釈:

  adler32 や crc32 ハッシュ関数は "zlib" モジュールで提供されています
  。


ハッシュアルゴリズム
====================

There is one constructor method named for each type of *hash*.  All
return a hash object with the same simple interface. For example: use
"sha256()" to create a SHA-256 hash object. You can now feed this
object with *bytes-like objects* (normally "bytes") using the "update"
method.  At any point you can ask it for the *digest* of the
concatenation of the data fed to it so far using the "digest()" or
"hexdigest()" methods.

To allow multithreading, the Python *GIL* is released while computing
a hash supplied more than 2047 bytes of data at once in its
constructor or ".update" method.

Constructors for hash algorithms that are always present in this
module are "sha1()", "sha224()", "sha256()", "sha384()", "sha512()",
"sha3_224()", "sha3_256()", "sha3_384()", "sha3_512()", "shake_128()",
"shake_256()", "blake2b()", and "blake2s()". "md5()" is normally
available as well, though it may be missing or blocked if you are
using a rare "FIPS compliant" build of Python. These correspond to
"algorithms_guaranteed".

Additional algorithms may also be available if your Python
distribution's "hashlib" was linked against a build of OpenSSL that
provides others. Others *are not guaranteed available* on all
installations and will only be accessible by name via "new()".  See
"algorithms_available".

警告:

  Some algorithms have known hash collision weaknesses (including MD5
  and SHA1). Refer to Attacks on cryptographic hash algorithms and the
  hashlib-seealso section at the end of this document.

Added in version 3.6: SHA3 (Keccak) and SHAKE constructors
"sha3_224()", "sha3_256()", "sha3_384()", "sha3_512()", "shake_128()",
"shake_256()" were added. "blake2b()" and "blake2s()" were added.

バージョン 3.9 で変更: All hashlib constructors take a keyword-only
argument *usedforsecurity* with default value "True". A false value
allows the use of insecure and blocked hashing algorithms in
restricted environments. "False" indicates that the hashing algorithm
is not used in a security context, e.g. as a non-cryptographic one-way
compression function.

バージョン 3.9 で変更: Hashlib now uses SHA3 and SHAKE from OpenSSL if
it provides it.

バージョン 3.12 で変更: For any of the MD5, SHA1, SHA2, or SHA3
algorithms that the linked OpenSSL does not provide we fall back to a
verified implementation from the HACL* project.


使用法
======

To obtain the digest of the byte string "b"Nobody inspects the
spammish repetition"":

   >>> import hashlib
   >>> m = hashlib.sha256()
   >>> m.update(b"Nobody inspects")
   >>> m.update(b" the spammish repetition")
   >>> m.digest()
   b'\x03\x1e\xdd}Ae\x15\x93\xc5\xfe\\\x00o\xa5u+7\xfd\xdf\xf7\xbcN\x84:\xa6\xaf\x0c\x95\x0fK\x94\x06'
   >>> m.hexdigest()
   '031edd7d41651593c5fe5c006fa5752b37fddff7bc4e843aa6af0c950f4b9406'

もっと簡潔に書くと、このようになります:

>>> hashlib.sha256(b"Nobody inspects the spammish repetition").hexdigest()
'031edd7d41651593c5fe5c006fa5752b37fddff7bc4e843aa6af0c950f4b9406'


Constructors
============

hashlib.new(name, [data, ]*, usedforsecurity=True)

   Is a generic constructor that takes the string *name* of the
   desired algorithm as its first parameter.  It also exists to allow
   access to the above listed hashes as well as any other algorithms
   that your OpenSSL library may offer.

Using "new()" with an algorithm name:

>>> h = hashlib.new('sha256')
>>> h.update(b"Nobody inspects the spammish repetition")
>>> h.hexdigest()
'031edd7d41651593c5fe5c006fa5752b37fddff7bc4e843aa6af0c950f4b9406'

hashlib.md5([data, ]*, usedforsecurity=True)

hashlib.sha1([data, ]*, usedforsecurity=True)

hashlib.sha224([data, ]*, usedforsecurity=True)

hashlib.sha256([data, ]*, usedforsecurity=True)

hashlib.sha384([data, ]*, usedforsecurity=True)

hashlib.sha512([data, ]*, usedforsecurity=True)

hashlib.sha3_224([data, ]*, usedforsecurity=True)

hashlib.sha3_256([data, ]*, usedforsecurity=True)

hashlib.sha3_384([data, ]*, usedforsecurity=True)

hashlib.sha3_512([data, ]*, usedforsecurity=True)

Named constructors such as these are faster than passing an algorithm
name to "new()".


属性
====

Hashlib provides the following constant module attributes:

hashlib.algorithms_guaranteed

   このモジュールによってすべてのプラットフォームでサポートされている
   ことが保証されるハッシュアルゴリズムの名前を含む集合です。一部のア
   ップストリームのベンダーが提供する奇妙な "FIPS準拠の" Pythonビルド
   ではmd5のサポートを除外していますが、その場合であっても 'md5' がリ
   ストに含まれることに注意してください。

   Added in version 3.2.

hashlib.algorithms_available

   実行中の Python インタープリタで利用可能なハッシュアルゴリズム名の
   set です。これらの名前は "new()" に渡すことができます。
   "algorithms_guaranteed" は常にサブセットです。この set の中に同じア
   ルゴリズムが違う名前で複数回現れることがあります (OpenSSL 由来)。

   Added in version 3.2.


Hash Objects
============

コンストラクタが返すハッシュオブジェクトには、次のような定数属性が用意
されています:

hash.digest_size

   生成されたハッシュのバイト数。

hash.block_size

   内部で使われるハッシュアルゴリズムのブロックのバイト数。

ハッシュオブジェクトには次のような属性があります:

hash.name

   このハッシュの正規名です。常に小文字で、"new()" の引数として渡して
   このタイプの別のハッシュを生成することができます。

   バージョン 3.4 で変更: name 属性は CPython には最初からありましたが
   、Python 3.4 までは正式に明記されていませんでした。そのため、プラッ
   トフォームによっては存在しないかもしれません。

ハッシュオブジェクトには次のようなメソッドがあります:

hash.update(data)

   hash オブジェクトを *bytes-like object* で更新します。このメソッド
   の呼出しの繰り返しは、それらの引数を全て結合した引数で単一の呼び出
   しをした際と同じになります。すなわち "m.update(a); m.update(b)"  は
   "m.update(a + b)" と等価です。

hash.digest()

   これまで "update()" メソッドに渡されたデータのダイジェスト値を返し
   ます。これは "digest_size" と同じ長さの、0 から 255 の範囲全てを含
   み得るバイトの列です。

hash.hexdigest()

   "digest()" と似ていますが、倍の長さの、16進形式文字列を返します。こ
   れは、電子メールなどの非バイナリ環境で値を交換する場合に便利です。

hash.copy()

   ハッシュオブジェクトのコピー ("クローン") を返します。これは、最初
   の部分文字列が共通なデータのダイジェストを効率的に計算するために使
   用します。


SHAKE 可変長ダイジェスト
========================

hashlib.shake_128([data, ]*, usedforsecurity=True)

hashlib.shake_256([data, ]*, usedforsecurity=True)

The "shake_128()" and "shake_256()" algorithms provide variable length
digests with length_in_bits//2 up to 128 or 256 bits of security. As
such, their digest methods require a length. Maximum length is not
limited by the SHAKE algorithm.

shake.digest(length)

   Return the digest of the data passed to the "update()" method so
   far. This is a bytes object of size *length* which may contain
   bytes in the whole range from 0 to 255.

shake.hexdigest(length)

   Like "digest()" except the digest is returned as a string object of
   double length, containing only hexadecimal digits.  This may be
   used to exchange the value in email or other non-binary
   environments.

Example use:

>>> h = hashlib.shake_256(b'Nobody inspects the spammish repetition')
>>> h.hexdigest(20)
'44709d6fcb83d92a76dcb0b668c98e1b1d3dafe7'


File hashing
============

The hashlib module provides a helper function for efficient hashing of
a file or file-like object.

hashlib.file_digest(fileobj, digest, /)

   Return a digest object that has been updated with contents of file
   object.

   *fileobj* must be a file-like object opened for reading in binary
   mode. It accepts file objects from  builtin "open()", "BytesIO"
   instances, SocketIO objects from "socket.socket.makefile()", and
   similar. The function may bypass Python's I/O and use the file
   descriptor from "fileno()" directly. *fileobj* must be assumed to
   be in an unknown state after this function returns or raises. It is
   up to the caller to close *fileobj*.

   *digest* must either be a hash algorithm name as a *str*, a hash
   constructor, or a callable that returns a hash object.

   例:

   >>> import io, hashlib, hmac
   >>> with open(hashlib.__file__, "rb") as f:
   ...     digest = hashlib.file_digest(f, "sha256")
   ...
   >>> digest.hexdigest()  
   '...'

   >>> buf = io.BytesIO(b"somedata")
   >>> mac1 = hmac.HMAC(b"key", digestmod=hashlib.sha512)
   >>> digest = hashlib.file_digest(buf, lambda: mac1)

   >>> digest is mac1
   True
   >>> mac2 = hmac.HMAC(b"key", b"somedata", digestmod=hashlib.sha512)
   >>> mac1.digest() == mac2.digest()
   True

   Added in version 3.11.


鍵導出
======

鍵の導出 (derivation) と引き伸ばし (stretching) のアルゴリズムはセキュ
アなパスワードのハッシュ化のために設計されました。 "sha1(password)" の
ような甘いアルゴリズムは、ブルートフォース攻撃に抵抗できません。良いパ
スワードハッシュ化は調節可能で、遅くて、 salt を含まなければなりません
。

hashlib.pbkdf2_hmac(hash_name, password, salt, iterations, dklen=None)

   この関数は PKCS#5 のパスワードに基づいた鍵導出関数 2 を提供していま
   す。疑似乱数関数として HMAC を使用しています。

   文字列 *hash_name* は、HMAC のハッシュダイジェストアルゴリズムの望
   ましい名前で、例えば 'sha1' や 'sha256' です。 *password* と *salt*
   はバイト列のバッファとして解釈されます。アプリケーションとライブラ
   リは、 *password* を適切な長さ (例えば 1024) に制限すべきです。
   *salt* は "os.urandom()" のような適切なソースからの、およそ 16 バイ
   トかそれ以上のバイト列にするべきです。

   The number of *iterations* should be chosen based on the hash
   algorithm and computing power. As of 2022, hundreds of thousands of
   iterations of SHA-256 are suggested. For rationale as to why and
   how to choose what is best for your application, read *Appendix
   A.2.2* of NIST-SP-800-132. The answers on the stackexchange pbkdf2
   iterations question explain in detail.

   *dklen* is the length of the derived key in bytes. If *dklen* is
   "None" then the digest size of the hash algorithm *hash_name* is
   used, e.g. 64 for SHA-512.

   >>> from hashlib import pbkdf2_hmac
   >>> our_app_iters = 500_000  # Application specific, read above.
   >>> dk = pbkdf2_hmac('sha256', b'password', b'bad salt' * 2, our_app_iters)
   >>> dk.hex()
   '15530bba69924174860db778f2c6f8104d3aaf9d26241840c8c4a641c8d000a9'

   Function only available when Python is compiled with OpenSSL.

   Added in version 3.4.

   バージョン 3.12 で変更: Function now only available when Python is
   built with OpenSSL. The slow pure Python implementation has been
   removed.

hashlib.scrypt(password, *, salt, n, r, p, maxmem=0, dklen=64)

   この関数は、 **RFC 7914** で定義されるscrypt のパスワードに基づいた
   鍵導出関数を提供します。

   *password* と *salt* は *bytes-like object* でなければなりません。
   アプリケーションとライブラリは、 *password* を適切な長さ (例えば
   1024) に制限すべきです。 *salt* は "os.urandom()" のような適切なソ
   ースからの、およそ 16 バイトかそれ以上のバイト列にするべきです。

   *n* is the CPU/Memory cost factor, *r* the block size, *p*
   parallelization factor and *maxmem* limits memory (OpenSSL 1.1.0
   defaults to 32 MiB). *dklen* is the length of the derived key in
   bytes.

   Added in version 3.6.


BLAKE2
======

BLAKE2 is a cryptographic hash function defined in **RFC 7693** that
comes in two flavors:

* **BLAKE2b**, optimized for 64-bit platforms and produces digests of
  any size between 1 and 64 bytes,

* **BLAKE2s**, optimized for 8- to 32-bit platforms and produces
  digests of any size between 1 and 32 bytes.

BLAKE2 supports **keyed mode** (a faster and simpler replacement for
HMAC), **salted hashing**, **personalization**, and **tree hashing**.

このモジュールのハッシュオブジェクトは標準ライブラリーの "hashlib" オ
ブジェクトの API に従います。


ハッシュオブジェクトの作成
--------------------------

新しいハッシュオブジェクトは、コンストラクタ関数を呼び出すことで生成さ
れます:

hashlib.blake2b(data=b'', *, digest_size=64, key=b'', salt=b'', person=b'', fanout=1, depth=1, leaf_size=0, node_offset=0, node_depth=0, inner_size=0, last_node=False, usedforsecurity=True)

hashlib.blake2s(data=b'', *, digest_size=32, key=b'', salt=b'', person=b'', fanout=1, depth=1, leaf_size=0, node_offset=0, node_depth=0, inner_size=0, last_node=False, usedforsecurity=True)

These functions return the corresponding hash objects for calculating
BLAKE2b or BLAKE2s. They optionally take these general parameters:

* *data*: initial chunk of data to hash, which must be *bytes-like
  object*.  It can be passed only as positional argument.

* *digest_size*: 出力するダイジェストのバイト数。

* *key*: key for keyed hashing (up to 64 bytes for BLAKE2b, up to 32
  bytes for BLAKE2s).

* *salt*: salt for randomized hashing (up to 16 bytes for BLAKE2b, up
  to 8 bytes for BLAKE2s).

* *person*: personalization string (up to 16 bytes for BLAKE2b, up to
  8 bytes for BLAKE2s).

下の表は一般的なパラメータの上限 (バイト単位) です:

+---------+-------------+----------+-----------+-------------+
| Hash    | digest_size | len(key) | len(salt) | len(person) |
|=========|=============|==========|===========|=============|
| BLAKE2b | 64          | 64       | 16        | 16          |
+---------+-------------+----------+-----------+-------------+
| BLAKE2s | 32          | 32       | 8         | 8           |
+---------+-------------+----------+-----------+-------------+

注釈:

  BLAKE2 specification defines constant lengths for salt and
  personalization parameters, however, for convenience, this
  implementation accepts byte strings of any size up to the specified
  length. If the length of the parameter is less than specified, it is
  padded with zeros, thus, for example, "b'salt'" and "b'salt\x00'" is
  the same value. (This is not the case for *key*.)

これらのサイズは以下に述べるモジュール constants で利用できます。

コンストラクタ関数は以下のツリーハッシングパラメタを受け付けます:

* *fanout*: fanout (0 to 255, 0 if unlimited, 1 in sequential mode).

* *depth*: ツリーの深さの最大値（1から255までの値で、無制限であれば255
  、シーケンスモードでは1）。

* *leaf_size*: maximal byte length of leaf (0 to "2**32-1", 0 if
  unlimited or in sequential mode).

* *node_offset*: node offset (0 to "2**64-1" for BLAKE2b, 0 to
  "2**48-1" for BLAKE2s, 0 for the first, leftmost, leaf, or in
  sequential mode).

* *node_depth*: node depth (0 to 255, 0 for leaves, or in sequential
  mode).

* *inner_size*: inner digest size (0 to 64 for BLAKE2b, 0 to 32 for
  BLAKE2s, 0 in sequential mode).

* *last_node*: boolean indicating whether the processed node is the
  last one ("False" for sequential mode).

   [画像: Explanation of tree mode parameters.][画像]

See section 2.10 in BLAKE2 specification for comprehensive review of
tree hashing.


定数
----

blake2b.SALT_SIZE

blake2s.SALT_SIZE

ソルト長（コンストラクタが受け付けれる最大長）

blake2b.PERSON_SIZE

blake2s.PERSON_SIZE

Personalization string length (maximum length accepted by
constructors).

blake2b.MAX_KEY_SIZE

blake2s.MAX_KEY_SIZE

最大キー長

blake2b.MAX_DIGEST_SIZE

blake2s.MAX_DIGEST_SIZE

ハッシュ関数が出力しうるダイジェストの最大長


使用例
------


簡単なハッシュ化
~~~~~~~~~~~~~~~~

To calculate hash of some data, you should first construct a hash
object by calling the appropriate constructor function ("blake2b()" or
"blake2s()"), then update it with the data by calling "update()" on
the object, and, finally, get the digest out of the object by calling
"digest()" (or "hexdigest()" for hex-encoded string).

>>> from hashlib import blake2b
>>> h = blake2b()
>>> h.update(b'Hello world')
>>> h.hexdigest()
'6ff843ba685842aa82031d3f53c48b66326df7639a63d128974c5c14f31a0f33343a8c65551134ed1ae0f2b0dd2bb495dc81039e3eeb0aa1bb0388bbeac29183'

As a shortcut, you can pass the first chunk of data to update directly
to the constructor as the positional argument:

>>> from hashlib import blake2b
>>> blake2b(b'Hello world').hexdigest()
'6ff843ba685842aa82031d3f53c48b66326df7639a63d128974c5c14f31a0f33343a8c65551134ed1ae0f2b0dd2bb495dc81039e3eeb0aa1bb0388bbeac29183'

You can call "hash.update()" as many times as you need to iteratively
update the hash:

>>> from hashlib import blake2b
>>> items = [b'Hello', b' ', b'world']
>>> h = blake2b()
>>> for item in items:
...     h.update(item)
...
>>> h.hexdigest()
'6ff843ba685842aa82031d3f53c48b66326df7639a63d128974c5c14f31a0f33343a8c65551134ed1ae0f2b0dd2bb495dc81039e3eeb0aa1bb0388bbeac29183'


Using different digest sizes
~~~~~~~~~~~~~~~~~~~~~~~~~~~~

BLAKE2 はダイジェストの長さを、BLAKE2bでは64バイトまで、BLAKE2sでは32
バイトまでのダイジェスト長を指定できます。例えばSHA-1を、出力を同じ長
さのままでBLAKE2bで置き換えるには、BLAKE2bに20バイトのダイジェストを生
成するように指示できます:

>>> from hashlib import blake2b
>>> h = blake2b(digest_size=20)
>>> h.update(b'Replacing SHA1 with the more secure function')
>>> h.hexdigest()
'd24f26cf8de66472d58d4e1b1774b4c9158b1f4c'
>>> h.digest_size
20
>>> len(h.digest())
20

Hash objects with different digest sizes have completely different
outputs (shorter hashes are *not* prefixes of longer hashes); BLAKE2b
and BLAKE2s produce different outputs even if the output length is the
same:

>>> from hashlib import blake2b, blake2s
>>> blake2b(digest_size=10).hexdigest()
'6fa1d8fcfd719046d762'
>>> blake2b(digest_size=11).hexdigest()
'eb6ec15daf9546254f0809'
>>> blake2s(digest_size=10).hexdigest()
'1bf21a98c78a1c376ae9'
>>> blake2s(digest_size=11).hexdigest()
'567004bf96e4a25773ebf4'


Keyed hashing
~~~~~~~~~~~~~

Keyed hashing can be used for authentication as a faster and simpler
replacement for Hash-based message authentication code (HMAC). BLAKE2
can be securely used in prefix-MAC mode thanks to the
indifferentiability property inherited from BLAKE.

This example shows how to get a (hex-encoded) 128-bit authentication
code for message "b'message data'" with key "b'pseudorandom key'":

   >>> from hashlib import blake2b
   >>> h = blake2b(key=b'pseudorandom key', digest_size=16)
   >>> h.update(b'message data')
   >>> h.hexdigest()
   '3d363ff7401e02026f4a4687d4863ced'

As a practical example, a web application can symmetrically sign
cookies sent to users and later verify them to make sure they weren't
tampered with:

   >>> from hashlib import blake2b
   >>> from hmac import compare_digest
   >>>
   >>> SECRET_KEY = b'pseudorandomly generated server secret key'
   >>> AUTH_SIZE = 16
   >>>
   >>> def sign(cookie):
   ...     h = blake2b(digest_size=AUTH_SIZE, key=SECRET_KEY)
   ...     h.update(cookie)
   ...     return h.hexdigest().encode('utf-8')
   >>>
   >>> def verify(cookie, sig):
   ...     good_sig = sign(cookie)
   ...     return compare_digest(good_sig, sig)
   >>>
   >>> cookie = b'user-alice'
   >>> sig = sign(cookie)
   >>> print("{0},{1}".format(cookie.decode('utf-8'), sig))
   user-alice,b'43b3c982cf697e0c5ab22172d1ca7421'
   >>> verify(cookie, sig)
   True
   >>> verify(b'user-bob', sig)
   False
   >>> verify(cookie, b'0102030405060708090a0b0c0d0e0f00')
   False

Even though there's a native keyed hashing mode, BLAKE2 can, of
course, be used in HMAC construction with "hmac" module:

   >>> import hmac, hashlib
   >>> m = hmac.new(b'secret key', digestmod=hashlib.blake2s)
   >>> m.update(b'message')
   >>> m.hexdigest()
   'e3c8102868d28b5ff85fc35dda07329970d1a01e273c37481326fe0c861c8142'


Randomized hashing
~~~~~~~~~~~~~~~~~~

By setting *salt* parameter users can introduce randomization to the
hash function. Randomized hashing is useful for protecting against
collision attacks on the hash function used in digital signatures.

   Randomized hashing is designed for situations where one party, the
   message preparer, generates all or part of a message to be signed
   by a second party, the message signer. If the message preparer is
   able to find cryptographic hash function collisions (i.e., two
   messages producing the same hash value), then they might prepare
   meaningful versions of the message that would produce the same hash
   value and digital signature, but with different results (e.g.,
   transferring $1,000,000 to an account, rather than $10).
   Cryptographic hash functions have been designed with collision
   resistance as a major goal, but the current concentration on
   attacking cryptographic hash functions may result in a given
   cryptographic hash function providing less collision resistance
   than expected. Randomized hashing offers the signer additional
   protection by reducing the likelihood that a preparer can generate
   two or more messages that ultimately yield the same hash value
   during the digital signature generation process --- even if it is
   practical to find collisions for the hash function. However, the
   use of randomized hashing may reduce the amount of security
   provided by a digital signature when all portions of the message
   are prepared by the signer.

   (NIST SP-800-106 "Randomized Hashing for Digital Signatures")

In BLAKE2 the salt is processed as a one-time input to the hash
function during initialization, rather than as an input to each
compression function.

警告:

  *Salted hashing* (or just hashing) with BLAKE2 or any other general-
  purpose cryptographic hash function, such as SHA-256, is not
  suitable for hashing passwords.  See BLAKE2 FAQ for more
  information.

>>> import os
>>> from hashlib import blake2b
>>> msg = b'some message'
>>> # Calculate the first hash with a random salt.
>>> salt1 = os.urandom(blake2b.SALT_SIZE)
>>> h1 = blake2b(salt=salt1)
>>> h1.update(msg)
>>> # Calculate the second hash with a different random salt.
>>> salt2 = os.urandom(blake2b.SALT_SIZE)
>>> h2 = blake2b(salt=salt2)
>>> h2.update(msg)
>>> # The digests are different.
>>> h1.digest() != h2.digest()
True


Personalization
~~~~~~~~~~~~~~~

Sometimes it is useful to force hash function to produce different
digests for the same input for different purposes. Quoting the authors
of the Skein hash function:

   We recommend that all application designers seriously consider
   doing this; we have seen many protocols where a hash that is
   computed in one part of the protocol can be used in an entirely
   different part because two hash computations were done on similar
   or related data, and the attacker can force the application to make
   the hash inputs the same. Personalizing each hash function used in
   the protocol summarily stops this type of attack.

   (The Skein Hash Function Family, p. 21)

BLAKE2は *person* 引数にバイト列を渡すことでパーソナライズできます:

   >>> from hashlib import blake2b
   >>> FILES_HASH_PERSON = b'MyApp Files Hash'
   >>> BLOCK_HASH_PERSON = b'MyApp Block Hash'
   >>> h = blake2b(digest_size=32, person=FILES_HASH_PERSON)
   >>> h.update(b'the same content')
   >>> h.hexdigest()
   '20d9cd024d4fb086aae819a1432dd2466de12947831b75c5a30cf2676095d3b4'
   >>> h = blake2b(digest_size=32, person=BLOCK_HASH_PERSON)
   >>> h.update(b'the same content')
   >>> h.hexdigest()
   'cf68fb5761b9c44e7878bfb2c4c9aea52264a80b75005e65619778de59f383a3'

Personalization together with the keyed mode can also be used to
derive different keys from a single one.

>>> from hashlib import blake2s
>>> from base64 import b64decode, b64encode
>>> orig_key = b64decode(b'Rm5EPJai72qcK3RGBpW3vPNfZy5OZothY+kHY6h21KM=')
>>> enc_key = blake2s(key=orig_key, person=b'kEncrypt').digest()
>>> mac_key = blake2s(key=orig_key, person=b'kMAC').digest()
>>> print(b64encode(enc_key).decode('utf-8'))
rbPb15S/Z9t+agffno5wuhB77VbRi6F9Iv2qIxU7WHw=
>>> print(b64encode(mac_key).decode('utf-8'))
G9GtHFE1YluXY1zWPlYk1e/nWfu0WSEb0KRcjhDeP/o=


ツリーモード
~~~~~~~~~~~~

これが二つの葉ノードからなる最小の木をハッシュする例です:

     10
    /  \
   00  01

次の例では、64バイトの内部桁が使われ、32バイトの最終的なダイジェストを
返しています:

   >>> from hashlib import blake2b
   >>>
   >>> FANOUT = 2
   >>> DEPTH = 2
   >>> LEAF_SIZE = 4096
   >>> INNER_SIZE = 64
   >>>
   >>> buf = bytearray(6000)
   >>>
   >>> # Left leaf
   ... h00 = blake2b(buf[0:LEAF_SIZE], fanout=FANOUT, depth=DEPTH,
   ...               leaf_size=LEAF_SIZE, inner_size=INNER_SIZE,
   ...               node_offset=0, node_depth=0, last_node=False)
   >>> # Right leaf
   ... h01 = blake2b(buf[LEAF_SIZE:], fanout=FANOUT, depth=DEPTH,
   ...               leaf_size=LEAF_SIZE, inner_size=INNER_SIZE,
   ...               node_offset=1, node_depth=0, last_node=True)
   >>> # Root node
   ... h10 = blake2b(digest_size=32, fanout=FANOUT, depth=DEPTH,
   ...               leaf_size=LEAF_SIZE, inner_size=INNER_SIZE,
   ...               node_offset=0, node_depth=1, last_node=True)
   >>> h10.update(h00.digest())
   >>> h10.update(h01.digest())
   >>> h10.hexdigest()
   '3ad2a9b37c6070e374c7a8c508fe20ca86b6ed54e286e93a0318e95e881db5aa'


クレジット:
-----------

BLAKE2 は*Jean-Philippe Aumasson*、 *Luca Henzen*、 *Willi Meier* そし
て *Raphael C.-W. Phan* によって作成された SHA-3 の最終候補である
BLAKE  を元に、*Jean-Philippe Aumasson*、 *Samuel Neves*、 *Zooko
Wilcox-O'Hearn*, そして *Christian Winnerlein* によって設計されました
。

それは、 *Daniel J.  Bernstein* によって設計されたChaCha 暗号由来のア
ルゴリズムを用いています。

標準ライブラリは pyblake2 モジュールを基礎として実装されています。 こ
のモジュールは *Dmitry Chestnykh* によって、*Samuel Neves* が作成した
C実装を元に書かれました。 このドキュメントは、pyblake2 からコピーされ
、*Dmitry Chestnykh* によって書かれました。

*Christian Heimes* によって、一部のCコードがPython向けに書き直されまし
た。

以下の public domain dedicationが、Cのハッシュ関数実装と、拡張コードと
、このドキュメントに適用されます:

   To the extent possible under law, the author(s) have dedicated all
   copyright and related and neighboring rights to this software to
   the public domain worldwide. This software is distributed without
   any warranty.

   You should have received a copy of the CC0 Public Domain Dedication
   along with this software. If not, see
   https://creativecommons.org/publicdomain/zero/1.0/.

The following people have helped with development or contributed their
changes to the project and the public domain according to the Creative
Commons Public Domain Dedication 1.0 Universal:

* *Alexandr Sokolovskiy*

参考:

  "hmac" モジュール
     ハッシュを用いてメッセージ認証コードを生成するモジュールです。

  "base64" モジュール
     バイナリハッシュを非バイナリ環境用にエンコードするもうひとつの方
     法です。

  https://nvlpubs.nist.gov/nistpubs/fips/nist.fips.180-4.pdf
     The FIPS 180-4 publication on Secure Hash Algorithms.

  https://csrc.nist.gov/publications/detail/fips/202/final
     The FIPS 202 publication on the SHA-3 Standard.

  https://www.blake2.net/
     BLAKE2 の公式ウェブサイト

  https://en.wikipedia.org/wiki/Cryptographic_hash_function
     どのアルゴリズムにどんな既知の問題があって、それが実際に利用する
     際にどう影響するかについての Wikipedia の記事。

  https://www.ietf.org/rfc/rfc8018.txt
     PKCS #5: Password-Based Cryptography Specification Version 2.1

  https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication8
  00-132.pdf
     NIST Recommendation for Password-Based Key Derivation.
