sam.hadow/CSS-cipher
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encrypt, return bytes object instead of integer

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This commit is contained in:
Sam Hadow 2024-04-22 12:54:38 +02:00
parent 05a0cb2aa0
commit 71175c8ebd
2 changed files with 29 additions and 7 deletions
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1
.gitignore vendored
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@ -4,3 +4,4 @@
.swp.* .swp.*
*.pdf *.pdf
*.jpg

35
main.py
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@ -56,11 +56,17 @@ def css_encrypt(text, key):
lfsr17 = lfsr((key[:16]+[1]), taps17) lfsr17 = lfsr((key[:16]+[1]), taps17)
taps25 = [0, 3, 4, 12] taps25 = [0, 3, 4, 12]
lfsr25 = lfsr((key[16:]+[1]), taps25) lfsr25 = lfsr((key[16:]+[1]), taps25)
cipher_text = 0 cipher = 0
carry = 0 carry = 0
bytes = text.to_bytes((text.bit_length() + 7) // 8, 'big')
for byte in bytes: if isinstance(text, int):
Bytes = text.to_bytes((text.bit_length() + 7) // 8, 'big')
elif isinstance(text, bytes):
Bytes = text
else:
raise TypeError("input text should be bytes or integer")
for byte in Bytes:
x_b2 = "" x_b2 = ""
y_b2 = "" y_b2 = ""
# Generate bytes from lfsr17 and lfsr25 # Generate bytes from lfsr17 and lfsr25
@ -74,17 +80,32 @@ def css_encrypt(text, key):
carry = 1 if x + y > 255 else 0 carry = 1 if x + y > 255 else 0
cipher_byte = z ^ byte cipher_byte = z ^ byte
cipher_text = (cipher_text << 8) | cipher_byte # print(cipher_byte.to_bytes((cipher_byte.bit_length() + 7) // 8, 'big'))
return cipher_text cipher = (cipher << 8) | cipher_byte
cipher_bytes = b'\x00'*(len(Bytes) - len(cipher.to_bytes((cipher.bit_length() + 7) // 8, 'big'))) +cipher.to_bytes((cipher.bit_length() + 7) // 8, 'big') # padding
return cipher_bytes
def test_encrypt(): def test_encrypt():
print("test encryption: text 0xffffffffff, key 0x0 ∈ {0, 1}^40") print("test encryption: text 0xffffffffff, key 0x0 ∈ {0, 1}^40")
cipher = css_encrypt(0xffffffffff, [0]*40) cipher = int.from_bytes(css_encrypt(0xffffffffff, [0]*40), byteorder='big')
print(f'cipher: {hex(cipher)}') print(f'cipher: {hex(cipher)}')
clear = css_encrypt(cipher, [0]*40) clear = int.from_bytes(css_encrypt(cipher, [0]*40))
print(f'decrypted: {hex(clear)}') print(f'decrypted: {hex(clear)}')
print(f'original text and decrypted message are the same: {clear==0xffffffffff}') print(f'original text and decrypted message are the same: {clear==0xffffffffff}')
def gen_6_bytes():
# key = [randint(0, 1) for _ in range(40)]
# key = [1, 1, 0, 0, 1, 1, 0, 1, 1, 0, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0]
key = [0]*40
text = b'\x00\x00\x00\x00\x00\x00'
print(key)
cipher = css_encrypt(text, key)
print(cipher)
print(css_encrypt(cipher, key))
return cipher
test_lfsr17() test_lfsr17()
print() print()
test_encrypt() test_encrypt()
print()
gen_6_bytes()