用python实现Salsa算法
时间: 2024-05-16 07:14:01 浏览: 196
Salsa算法是一种流密码算法,可以用于加密和解密数据。下面是用Python实现Salsa20算法的示例代码:
```python
import struct
def rotate_left(x, n):
return ((x << n) & 0xffffffff) | (x >> (32 - n))
def salsa20_block(key, nonce, counter):
sigma = b"expand 32-byte k"
tau = b"expand 16-byte k"
state = [
struct.unpack("<I", sigma[i:i+4])[0] for i in range(0, len(sigma), 4)
] + key + [counter & 0xffffffff, (counter >> 32) & 0xffffffff] + \
[struct.unpack("<I", nonce[i:i+4])[0] for i in range(0, len(nonce), 4)]
output = list(state)
for i in range(10):
output[ 4] ^= rotate_left(output[ 0] + output[12], 7)
output[ 8] ^= rotate_left(output[ 4] + output[ 0], 9)
output[12] ^= rotate_left(output[ 8] + output[ 4],13)
output[ 0] ^= rotate_left(output[12] + output[ 8],18)
output[ 9] ^= rotate_left(output[ 5] + output[ 1], 7)
output[13] ^= rotate_left(output[ 9] + output[ 5], 9)
output[ 1] ^= rotate_left(output[13] + output[ 9],13)
output[ 5] ^= rotate_left(output[ 1] + output[13],18)
output[14] ^= rotate_left(output[10] + output[ 6], 7)
output[ 2] ^= rotate_left(output[14] + output[10], 9)
output[ 6] ^= rotate_left(output[ 2] + output[14],13)
output[10] ^= rotate_left(output[ 6] + output[ 2],18)
output[ 3] ^= rotate_left(output[15] + output[11], 7)
output[ 7] ^= rotate_left(output[ 3] + output[15], 9)
output[11] ^= rotate_left(output[ 7] + output[ 3],13)
output[15] ^= rotate_left(output[11] + output[ 7],18)
output[ 5] ^= rotate_left(output[ 1] + output[ 0], 7)
output[ 6] ^= rotate_left(output[ 2] + output[ 1], 9)
output[ 7] ^= rotate_left(output[ 3] + output[ 2],13)
output[ 4] ^= rotate_left(output[15] + output[14],18)
output[10] ^= rotate_left(output[ 6] + output[ 5], 7)
output[11] ^= rotate_left(output[ 7] + output[ 6], 9)
output[ 8] ^= rotate_left(output[ 4] + output[ 3],13)
output[ 9] ^= rotate_left(output[ 5] + output[ 4],18)
return bytes(
sum((
struct.pack("<I", (state[i] + output[i]) & 0xffffffff)
for i in range(len(state))
), ())
)
def salsa20(key, nonce, initial_counter=0):
counter = initial_counter
while True:
block = salsa20_block(key, nonce, counter)
yield block
counter = (counter + 1) & 0xffffffff
if counter == 0:
raise ValueError("Ran out of Salsa20 blocks")
```
这里的`salsa20`函数可以用来生成Salsa20流密码。它接受一个密钥和一个随机数,然后生成一个无限的字节流。可以使用`next`函数逐个读取字节,或使用`itertools`模块中的`islice`函数获取特定数量的字节。下面是一个使用示例:
```python
import itertools
key = b"0123456789abcdef" * 2
nonce = b"01234567" * 2
stream = salsa20(key, nonce)
data = bytes(itertools.islice(stream, 1024))
```
这里使用了一个256位的密钥和64位的随机数,并生成了1024字节的流密码。
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