mirror of https://github.com/dirtbags/moth.git
49 lines
1.5 KiB
Python
49 lines
1.5 KiB
Python
|
#!/usr/bin/python3
|
||
|
|
|
||
|
|
plaintext = [b"This may seem relatively simple, but it's the same basic "
|
||
|
|
b"principles as used in s-boxes, a technique used in many modern "
|
||
|
|
b"cryptographic algoritms. Of course, instead of letter substitution, "
|
||
|
|
b"you're doing byte substitution.",
|
||
|
|
b"The next two puzzles are a bit different; Frequency counts (of characters) "
|
||
|
|
b"will just reveal random noise. "
|
||
|
|
b"Oh, by the way, the key this time is: 'the s is for sucks'."]
|
||
|
|
|
||
|
|
key = b"thequickbrownfxjmpdvlazygs"
|
||
|
|
|
||
|
|
def encode(text):
|
||
|
|
ukey = key.upper()
|
||
|
|
lkey = key.lower()
|
||
|
|
assert len(set(key)) == 26, 'invalid key'
|
||
|
|
assert key.isalpha(), 'non alpha character in key'
|
||
|
|
out = bytearray()
|
||
|
|
for t in text:
|
||
|
|
if t in lkey:
|
||
|
|
out.append(lkey[t - ord('a')])
|
||
|
|
elif t in ukey:
|
||
|
|
out.append(ukey[t - ord('A')])
|
||
|
|
else:
|
||
|
|
out.append(t)
|
||
|
|
return bytes(out)
|
||
|
|
|
||
|
|
def decode(text):
|
||
|
|
ukey = key.upper()
|
||
|
|
lkey = key.lower()
|
||
|
|
assert len(set(key)) == 26, 'invalid key'
|
||
|
|
assert key.isalpha(), 'non alpha character in key'
|
||
|
|
out = bytearray()
|
||
|
|
for t in text:
|
||
|
|
if t in lkey:
|
||
|
|
out.append(ord('a') + lkey.index(bytes([t])))
|
||
|
|
elif t in ukey:
|
||
|
|
out.append(ord('A') + ukey.index(bytes([t])))
|
||
|
|
else:
|
||
|
|
out.append(t)
|
||
|
|
return bytes(out)
|
||
|
|
|
||
|
|
c = encode(plaintext[0])
|
||
|
|
print('<dl><dt>Alice<dd>', str(c, 'utf-8'))
|
||
|
|
assert decode(c) == plaintext[0]
|
||
|
|
c = encode(plaintext[1])
|
||
|
|
print('<dt>Bob<dd>', str(c, 'utf-8'), '</dl>')
|
||
|
|
assert decode(c) == plaintext[1]
|