hashlib
— 安全哈希和消息摘要
¶
2.5 版新增。
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 ). The terms secure hash and message digest are interchangeable. Older algorithms were called message digests. The modern term is secure hash.
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
sha1()
to create a SHA1 hash object. You can now feed this object with arbitrary strings using the
update()
方法。在任何时候都可以向它请求
digest
of the concatenation of the strings fed to it so far using the
digest()
or
hexdigest()
方法。
此模块中始终存在的哈希算法构造函数包括
md5()
,
sha1()
,
sha224()
,
sha256()
,
sha384()
，和
sha512()
. Additional algorithms may also be available depending upon the OpenSSL library that Python uses on your platform.
For example, to obtain the digest of the string
'Nobody inspects the spammish
repetition'
:
>>> import hashlib
>>> m = hashlib.md5()
>>> m.update("Nobody inspects")
>>> m.update(" the spammish repetition")
>>> m.digest()
'\xbbd\x9c\x83\xdd\x1e\xa5\xc9\xd9\xde\xc9\xa1\x8d\xf0\xff\xe9'
>>> m.digest_size
16
>>> m.block_size
64
更浓缩：
>>> hashlib.sha224("Nobody inspects the spammish repetition").hexdigest()
'a4337bc45a8fc544c03f52dc550cd6e1e87021bc896588bd79e901e2'
A generic
new()
constructor that takes the string name of the desired algorithm as its first parameter 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('ripemd160')
>>> h.update("Nobody inspects the spammish repetition")
>>> h.hexdigest()
'cc4a5ce1b3df48aec5d22d1f16b894a0b894eccc'
This module provides the following constant attribute:
hashlib.
algorithms
¶
A tuple providing the names of the hash algorithms guaranteed to be supported by this module.
2.7 版新增。
hashlib.
algorithms_guaranteed
¶
A set containing the names of the hash algorithms guaranteed to be supported by this module on all platforms.
2.7.9 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).
2.7.9 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.
A hash object has the following methods:
hash.
update
(
arg
)
¶
Update the hash object with the string
arg
. 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)
.
2.7 版改变： The Python GIL is released to allow other threads to run while hash updates on data larger than 2048 bytes is taking place when using hash algorithms supplied by OpenSSL.
hash.
digest
(
)
¶
Return the digest of the strings passed to the
update()
method so far. This is a string of
digest_size
bytes which may contain non-ASCII characters, including null bytes.
hash.
hexdigest
(
)
¶
像
digest()
except the digest is returned as a string 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 strings that share a common initial substring.
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
(
名称
,
password
,
salt
,
rounds
,
dklen=None
)
¶
The function provides PKCS#5 password-based key derivation function 2. It uses HMAC as pseudorandom function.
字符串
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 value (e.g. 1024).
salt
should be about 16 or more bytes from a proper source, e.g.
os.urandom()
.
The number of rounds should be chosen based on the hash algorithm and computing power. As of 2013, at least 100,000 rounds of SHA-256 is suggested.
dklen
is the length of the derived key. If
dklen
is
None
then the digest size of the hash algorithm
name
is used, e.g. 64 for SHA-512.
>>> import hashlib, binascii
>>> dk = hashlib.pbkdf2_hmac('sha256', b'password', b'salt', 100000)
>>> binascii.hexlify(dk)
b'0394a2ede332c9a13eb82e9b24631604c31df978b4e2f0fbd2c549944f9d79a5'
New in version 2.7.8.
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.
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.
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.