hashlib
— 安全哈希和消息摘要
¶
源代码： Lib/hashlib.py
此模块实现了很多不同安全哈希和消息摘要算法的公共接口。包括 FIPS (联邦信息处理标准) 安全哈希算法 SHA1、SHA224、SHA256、SHA384、SHA512 （定义在 FIPS 180-2）及 RSA 的 MD5 算法 (定义在 Internet RFC 1321 )。术语 "安全哈希" 和 "消息摘要" 可互换。旧算法称为消息摘要。现代术语是安全哈希。
注意
若想要 adler32 (或 crc32) 哈希函数，可找到它们在
zlib
模块。
警告
某些算法有已知的哈希冲突弱点，参考结尾的 "另请参阅" 章节。
有一命名构造函数方法对于每种类型的
hash
。全部返回具有相同简单接口的哈希对象。例如：使用
sha256()
能创建 SHA-256 哈希对象。现在可以喂这种对象采用
像字节对象
(通常
bytes
) 使用
update()
方法。在任何时候都可以向它请求
digest
为喂给它的串联数据，到目前为止是使用
digest()
or
hexdigest()
方法。
注意
为获得更好的多线程性能，Python GIL 被释放，对于大于 2047 字节的数据，当创建 (或更新) 对象时。
注意
将字符串对象喂给
update()
不被支持，因为哈希工作于字节，但不工作于字符。
此模块中始终存在的哈希算法构造函数包括
sha1()
,
sha224()
,
sha256()
,
sha384()
,
sha512()
,
blake2b()
，和
blake2s()
.
md5()
通常也可用，即使它可能缺失，若正使用罕见 "FIPS 兼容" Python 构建。还可能找到其它算法，从属 Python 在您平台使用的 OpenSSL 库。在大多数平台
sha3_224()
,
sha3_256()
,
sha3_384()
,
sha3_512()
,
shake_128()
,
shake_256()
也可用。
3.6 版新增：
SHA3 (Keccak) 和 SHAKE 构造函数
sha3_224()
,
sha3_256()
,
sha3_384()
,
sha3_512()
,
shake_128()
,
shake_256()
.
3.6 版新增：
blake2b()
and
blake2s()
被添加。
例如，要获得摘要对于字节字符串
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.digest_size 32 >>> m.block_size 64
更浓缩：
>>> hashlib.sha224(b"Nobody inspects the spammish repetition").hexdigest() 'a4337bc45a8fc544c03f52dc550cd6e1e87021bc896588bd79e901e2'
hashlib.
new
(
name
[
,
data
]
)
¶
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. The named constructors are much faster than
new()
且应该是首选的。
使用
new()
采用由 OpenSSL 提供的算法：
>>> h = hashlib.new('sha512_256') >>> h.update(b"Nobody inspects the spammish repetition") >>> h.hexdigest() '19197dc4d03829df858011c6c87600f994a858103bbc19005f20987aa19a97e2'
Hashlib 提供下列常量属性：
hashlib.
algorithms_guaranteed
¶
A set containing the names of the hash algorithms guaranteed to be supported by this module on all platforms. Note that ‘md5’ is in this list despite some upstream vendors offering an odd “FIPS compliant” Python build that excludes it.
3.2 版新增。
hashlib.
algorithms_available
¶
A set containing the names of the hash algorithms that are available in the running Python interpreter. These names will be recognized when passed to
new()
.
algorithms_guaranteed
will always be a subset. The same algorithm may appear multiple times in this set under different names (thanks to OpenSSL).
3.2 版新增。
The following values are provided as constant attributes of the hash objects returned by the constructors:
hash.
digest_size
¶
哈希结果的大小 (以字节为单位)。
hash.
block_size
¶
The internal block size of the hash algorithm in bytes.
哈希对象拥有下列属性：
hash.
名称
¶
The canonical name of this hash, always lowercase and always suitable as a parameter to
new()
to create another hash of this type.
3.4 版改变： The name attribute has been present in CPython since its inception, but until Python 3.4 was not formally specified, so may not exist on some platforms.
A hash object has the following methods:
hash.
update
(
data
)
¶
更新哈希对象采用
像字节对象
. Repeated calls are equivalent to a single call with the concatenation of all the arguments:
m.update(a); m.update(b)
相当于
m.update(a+b)
.
3.1 版改变： The Python GIL is released to allow other threads to run while hash updates on data larger than 2047 bytes is taking place when using hash algorithms supplied by OpenSSL.
hash.
digest
(
)
¶
Return the digest of the data passed to the
update()
method so far. This is a bytes object of size
digest_size
which may contain bytes in the whole range from 0 to 255.
hash.
hexdigest
(
)
¶
像
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 safely in email or other non-binary environments.
hash.
copy
(
)
¶
Return a copy (“clone”) of the hash object. This can be used to efficiently compute the digests of data sharing a common initial substring.
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
)
¶
像
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 safely in email or other non-binary environments.
Key derivation and key stretching algorithms are designed for secure password hashing. Naive algorithms such as
sha1(password)
are not resistant against brute-force attacks. A good password hashing function must be tunable, slow, and include a
salt
.
hashlib.
pbkdf2_hmac
(
hash_name
,
password
,
salt
,
iterations
,
dklen=None
)
¶
The function provides PKCS#5 password-based key derivation function 2. It uses HMAC as pseudorandom function.
字符串
hash_name
is the desired name of the hash digest algorithm for HMAC, e.g. ‘sha1’ or ‘sha256’.
password
and
salt
are interpreted as buffers of bytes. Applications and libraries should limit
password
to a sensible length (e.g. 1024).
salt
should be about 16 or more bytes from a proper source, e.g.
os.urandom()
.
The number of iterations should be chosen based on the hash algorithm and computing power. As of 2013, at least 100,000 iterations of SHA-256 are suggested.
dklen
is the length of the derived key. If
dklen
is
None
then the digest size of the hash algorithm
hash_name
is used, e.g. 64 for SHA-512.
>>> import hashlib >>> dk = hashlib.pbkdf2_hmac('sha256', b'password', b'salt', 100000) >>> dk.hex() '0394a2ede332c9a13eb82e9b24631604c31df978b4e2f0fbd2c549944f9d79a5'
3.4 版新增。
注意
A fast implementation of
pbkdf2_hmac
is available with OpenSSL. The Python implementation uses an inline version of
hmac
. It is about three times slower and doesn’t release the GIL.
hashlib.
scrypt
(
password
,
*
,
salt
,
n
,
r
,
p
,
maxmem=0
,
dklen=64
)
¶
The function provides scrypt password-based key derivation function as defined in RFC 7914 .
password
and
salt
必须为
像字节对象
. Applications and libraries should limit
password
to a sensible length (e.g. 1024).
salt
should be about 16 or more bytes from a proper source, e.g.
os.urandom()
.
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.
可用性 : OpenSSL 1.1+.
3.6 版新增。
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 支持 keyed mode (a faster and simpler replacement for HMAC ), salted hashing , personalization ，和 tree hashing .
Hash objects from this module follow the API of standard library’s
hashlib
对象。
新哈希对象的创建是通过调用构造函数：
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
)
¶
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
)
¶
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 像字节对象 . It can be passed only as positional argument.
digest_size : size of output digest in bytes.
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).
The following table shows limits for general parameters (in bytes):
| 哈希 | digest_size | len(key) | len(salt) | len(person) |
|---|---|---|---|---|
| BLAKE2b | 64 | 64 | 16 | 16 |
| BLAKE2s | 32 | 32 | 8 | 8 |
注意
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
)。
These sizes are available as module constants described below.
Constructor functions also accept the following tree hashing parameters:
fanout : fanout (0 to 255, 0 if unlimited, 1 in sequential mode).
depth : maximal depth of tree (1 to 255, 255 if unlimited, 1 in sequential mode).
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).
See section 2.10 in BLAKE2 规范 for comprehensive review of tree hashing.
blake2b.
SALT_SIZE
¶
blake2s.
SALT_SIZE
¶
Salt length (maximum length accepted by constructors).
blake2b.
PERSON_SIZE
¶
blake2s.
PERSON_SIZE
¶
Personalization string length (maximum length accepted by constructors).
blake2b.
MAX_KEY_SIZE
¶
blake2s.
MAX_KEY_SIZE
¶
最大密钥大小。
blake2b.
MAX_DIGEST_SIZE
¶
blake2s.
MAX_DIGEST_SIZE
¶
Maximum digest size that the hash function can output.
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()
(或
hexdigest()
对于十六进制编码的字符串)。
>>> 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'
可以调用
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'
BLAKE2 has configurable size of digests up to 64 bytes for BLAKE2b and up to 32 bytes for BLAKE2s. For example, to replace SHA-1 with BLAKE2b without changing the size of output, we can tell BLAKE2b to produce 20-byte digests:
>>> 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 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'
采用键
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
模块：
>>> import hmac, hashlib >>> m = hmac.new(b'secret key', digestmod=hashlib.blake2s) >>> m.update(b'message') >>> m.hexdigest() 'e3c8102868d28b5ff85fc35dda07329970d1a01e273c37481326fe0c861c8142'
通过设置 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 了解更多信息。
>>> 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
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 can be personalized by passing bytes to the person 自变量：
>>> 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=
Here’s an example of hashing a minimal tree with two leaf nodes:
10 / \ 00 01
This example uses 64-byte internal digests, and returns the 32-byte final digest:
>>> 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'
BLAKE2 was designed by Jean-Philippe Aumasson , Samuel Neves , Zooko Wilcox-O’Hearn ，和 Christian Winnerlein 基于 SHA-3 finalist BLAKE created by Jean-Philippe Aumasson , Luca Henzen , Willi Meier ，和 Raphael C.-W. Phan .
It uses core algorithm from ChaCha cipher designed by Daniel J. Bernstein .
The stdlib implementation is based on pyblake2 module. It was written by Dmitry Chestnykh based on C implementation written by Samuel Neves . The documentation was copied from pyblake2 and written by Dmitry Chestnykh .
The C code was partly rewritten for Python by Christian Heimes .
The following public domain dedication applies for both C hash function implementation, extension code, and this documentation:
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
另请参阅
hmac
A module to generate message authentication codes using hashes.
base64
Another way to encode binary hashes for non-binary environments.
官方 BLAKE2 网站。
The FIPS 180-2 publication on Secure Hash Algorithms.
Wikipedia article with information on which algorithms have known issues and what that means regarding their use.
PKCS #5: Password-Based Cryptography Specification Version 2.0