SHA/Secure Hash Algorithm/安全散列算法
是一个密码散列函数家族,xxx认证的安全散列算法。能计算出一个数字消息所对应到的,长度固定的字符串(又称消息摘要)的算法。且若输入的消息不同,它们对应到不同字符串的机率很高。
case = u"readmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadmereadme"
import hashlib
x = hashlib.sha256()
x.update(case.encode())
print("SHA-256:" + x.hexdigest())
# SHA-256:740916e8f017fec0a2ef522f69c8f247494aa8b28375e778cbc572f4fc638159
# salted
import binascii
x = hashlib.pbkdf2_hmac("sha256", case.encode(), b"", 1)
print("SALTED SHA-256:" + binascii.hexlify(x).decode())
# SALTED SHA-256:b8bf9af6a1b05bd06bcbfbe1fbafe858aa97c0f91d40bd44a5192c3efc9c25fa
《SHA256算法原理详解》一文中作者的介绍把SHA-256分为了常量的初始化、信息预处理、逻辑运算三部分。其中常量初始化用了8个哈希初值(自然数中前8个质数2,3,5,7,11,13,17,19的平方根的小数部分取前32bit而来)和64个常量同平方根小数;预处理就是在想要Hash的消息后面补充需要的信息,使整个消息满足指定的结构,这里包括附加填充比特和附加长度;逻辑运算散列函数中涉及的操作全部是逻辑的位运算。
运行期计算时候:1. 将消息分解成512-bit大小的块; 2. 进行64次循环。
Note: All variables are unsigned 32 bits and wrap modulo 232 when calculating
Initialize variables
(first 32 bits of the fractional parts of the square roots of the first 8 primes 2..19):
h0 := 0x6a09e667
h1 := 0xbb67ae85
h2 := 0x3c6ef372
h3 := 0xa54ff53a
h4 := 0x510e527f
h5 := 0x9b05688c
h6 := 0x1f83d9ab
h7 := 0x5be0cd19
Initialize table of round constants
(first 32 bits of the fractional parts of the cube roots of the first 64 primes 2..311):
k[0..63] :=
0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2
Pre-processing:
append the bit '1' to the message
append k bits '0', where k is the minimum number >= 0 such that the resulting message
length (in bits) is congruent to 448(mod 512)
append length of message (before pre-processing), in bits, as 64-bit big-endian integer
Process the message in successive 512-bit chunks:
break message into 512-bit chunks
for each chunk
break chunk into sixteen 32-bit big-endian words w[0..15]
Extend the sixteen 32-bit words into sixty-four 32-bit words:
for i from 16 to 63
s0 := (w[i-15] rightrotate 7) xor (w[i-15] rightrotate 18) xor(w[i-15] rightshift 3)
s1 := (w[i-2] rightrotate 17) xor (w[i-2] rightrotate 19) xor(w[i-2] rightshift 10)
w[i] := w[i-16] + s0 + w[i-7] + s1
Initialize hash value for this chunk:
a := h0
b := h1
c := h2
d := h3
e := h4
f := h5
g := h6
h := h7
Main loop:
for i from 0 to 63
s0 := (a rightrotate 2) xor (a rightrotate 13) xor(a rightrotate 22)
maj := (a and b) xor (a and c) xor(b and c)
t2 := s0 + maj
s1 := (e rightrotate 6) xor (e rightrotate 11) xor(e rightrotate 25)
ch := (e and f) xor ((not e) and g)
t1 := h + s1 + ch + k[i] + w[i]
h := g
g := f
f := e
e := d + t1
d := c
c := b
b := a
a := t1 + t2
Add this chunk's hash to result so far:
h0 := h0 + a
h1 := h1 + b
h2 := h2 + c
h3 := h3 + d
h4 := h4 + e
h5 := h5 + f
h6 := h6 + g
h7 := h7 + h
Produce the final hash value (big-endian):
digest = hash = h0 append h1 append h2 append h3 append h4 append h5 append h6 append h7
单向的缩略信息可以用来校验不需要暴露原文,PKI Public Key Infrastructure, 这里主要是对这种公钥/非对称加密证书即CA Certificate Authority的管理...能开门就行什么抵赖不抵赖的碰撞不碰撞的...总是拿银行做对比,比如连Wi-Fi的 WPA2-PSK (PSK(SHA256))...问题在于,SHA256开头到的质数的情况就是个这么情况,科学技术的发展就是这么不讲武德...
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原创声明:本文系作者授权腾讯云开发者社区发表,未经许可,不得转载。
如有侵权,请联系 cloudcommunity@tencent.com 删除。