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This commit is contained in:
mwiegand 2021-06-20 20:59:45 +02:00
parent 89bc0976f7
commit fb0234bf3a
1 changed files with 29 additions and 22 deletions
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51
libs/derive_string.py
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@ -1,10 +1,16 @@
#!/usr/bin/env python #!/usr/bin/env python
from hashlib import sha3_256 from hashlib import sha3_256
from itertools import count from itertools import count, islice
from Crypto.Cipher import ChaCha20 from Crypto.Cipher import ChaCha20
from math import floor, ceil from math import floor, ceil
from time import sleep from time import sleep
from os import environ
from sys import stderr
def debug(*args):
if 'DEBUG' in environ:
print(*args, file=stderr)
def chacha_bits(input, bit_count): def chacha_bits(input, bit_count):
zerobyte = (0).to_bytes(length=1, byteorder='big') zerobyte = (0).to_bytes(length=1, byteorder='big')
@ -12,36 +18,37 @@ def chacha_bits(input, bit_count):
i = 0 i = 0
while True: while True:
print('-----------------------------') debug(f'--- BITS {i} ---')
start_bit = bit_count * i start_bit = bit_count * i
start_byte = start_bit // 8 start_byte = start_bit // 8
start_padding = start_bit % 8 start_padding = start_bit % 8
print('start_bit', start_bit) debug('start_bit', start_bit)
print('start_byte', start_byte) debug('start_byte', start_byte)
print('start_padding', start_padding) debug('start_padding', start_padding)
end_bit = bit_count * i + bit_count end_bit = bit_count * i + bit_count
end_byte = end_bit // 8 end_byte = end_bit // 8
end_padding = 8 - (end_bit % 8) end_padding = 8 - (end_bit % 8)
print('end_bit', end_bit) debug('end_bit', end_bit)
print('end_byte', end_byte) debug('end_byte', end_byte)
print('end_padding', end_padding) debug('end_padding', end_padding)
byte_count = (end_byte - start_byte) + 1 byte_count = (end_byte - start_byte) + 1
print('byte_count', byte_count) debug('byte_count', byte_count)
cipher.seek(start_byte) cipher.seek(start_byte)
ciphertext = cipher.encrypt(zerobyte*byte_count) cipherint = int.from_bytes(cipher.encrypt(zerobyte*byte_count), byteorder='big')
print('ciphertext', bin(int.from_bytes(ciphertext, byteorder='big'))) debug('ciphertext', bin(cipherint))
shifted_ciphertext = int.from_bytes(ciphertext, byteorder='big') >> end_padding shifted_cipherint = cipherint >> end_padding
print('shifted_ciphertext', bin(shifted_ciphertext)) debug('shifted_ciphertext', bin(shifted_cipherint))
bit_mask = int('1'*bit_count, 2) bit_mask = int('1'*bit_count, 2)
print('bit_mask', bin(bit_mask)) debug('bit_mask', bin(bit_mask))
masked_ciphertext = shifted_ciphertext & bit_mask masked_cipherint = shifted_cipherint & bit_mask
print('masked_ciphertext', bin(masked_ciphertext)) debug('masked_ciphertext', bin(masked_cipherint))
yield masked_ciphertext debug('')
yield masked_cipherint
i += 1 i += 1
@ -49,15 +56,15 @@ def chacha_chracter(input, choices):
get_bits = chacha_bits(input, len(choices).bit_length()) get_bits = chacha_bits(input, len(choices).bit_length())
while True: while True:
choice = next(get_bits) key = next(get_bits)
if choice < len(choices): if key < len(choices):
yield choices[choice] yield choices[key]
def derive_string(input, length, choices): def derive_string(input, length, choices):
get_character = chacha_chracter(input, choices) get_character = chacha_chracter(input, choices)
return ''.join(next(get_character) for i in range(length)) return bytes(islice(get_character, length))
print( print(
derive_string(b'12345', length=100, choices='abcdefghijklmnopqrstuvwxyz0123456789') derive_string(b'12344', length=100, choices=b'abcdefghijklmnopqrstuvwxyz0123456789')
) )