Unicode homoglyph secret message encoder/decoder

homoglyphs.txt

 ᅟᅠ         　ㅤ
!ǃ！
"″＂
$＄
%％
&＆
'＇
(﹝（
)﹞）
*⁎＊
+＋
,‚，
-‐－
.٠․‧。．｡
/ ̸⁄∕╱⫻⫽／ﾉ
0OoΟοОоՕＯｏ
1Iا１
2２
3３
4４
5５
6６
7７
8Ց８
9９
:։܃܄∶꞉：
;;；
>›＞
?？
@＠
[［
\＼
]］
^＾
_＿
`｀
AÀÁÂÃÄÅΑᎪＡ
aàáâãäåɑαаａ
BßʙΒβВᏴᛒＢ
bЬｂ
CϹСᏟⅭＣ
cϲсⅽｃ
DĎĐᎠⅮＤ
dďđԁժⅾｄ
EÈÉÊËĒĔĖĘĚΕЕᎬＥ
eéêëēĕėěеｅ
FϜＦ
fｆ
GɢԌնᏀＧ
gɡｇ
HʜΗНᎻＨ
hһｈ
IlΙІاᛁⅠＩ
iɩіᎥⅰｉ
JЈᎫＪ
jϳјյｊ
KΚКᏦᛕKＫ
kκｋ
LʟᏞⅬＬ
lιاⅼｌ
MΜϺМᎷᛖⅯＭ
mⅿｍ
NɴΝＮ
nｎ
O0ΟОՕＯ
oοоｏ
PΡРᏢＰ
pρрｐ
QႭႳＱ
qｑ
RʀᏒᚱＲ
rԻｒ
SЅՏႽᏚＳ
sѕｓ
TΤТᎢＴ
tτｔ
UԱՍ⋃Ｕ
uμυｕ
VѴᏙⅤⅴＶｖ
vνѵ
WᎳＷ
wѡｗ
XΧХⅩＸ
xχхⅹｘ
YʏΥҮＹ
yγуｙ
ZΖᏃＺ
zｚ
{｛
|ǀا｜
}｝
~⁓～
ßӧ
ÄӒ
ÖӦ

secret text.py

#!/usr/bin/env python3

import random
from functools import reduce

BIT_WIDTH = 5
CHAR_OFFSET = 65

f = open("homoglyphs.txt")
latinToHomoglyphs = {line[0]: line[1:-1] for line in f}
f.close()

def isHomoglyph(a):
    return a not in latinToHomoglyphs

def encode(message, secret):
    secret = secret.upper()
    assert len(message) >= len(secret)*BIT_WIDTH
    
    messageIndex = 0
    encoded = ""
    for c in secret:
        code = ord(c)-CHAR_OFFSET
        for i in range(BIT_WIDTH):
            if (code>>((BIT_WIDTH-1)-i))&1: encoded += random.choice(latinToHomoglyphs[message[messageIndex]])
            else: encoded += message[messageIndex]
            messageIndex += 1
    
    while messageIndex < len(message):
        encoded += message[messageIndex]
        messageIndex += 1
    
    return encoded

def decode(encoded):
    decoded = ""
    for messageIndex in range(0, len(encoded), BIT_WIDTH):
        chars = encoded[messageIndex:messageIndex+BIT_WIDTH]
        charsAreHomoglyph = map(isHomoglyph, chars)
        code = reduce(lambda a, b: a|b, [int(x)<<((BIT_WIDTH-1)-i) for i, x in enumerate(charsAreHomoglyph)])
        decoded += chr(code+CHAR_OFFSET)
    
    return decoded

if __name__ == "__main__":
    import sys
    if len(sys.argv) <= 2:
        print("Usage: {} [encode|decode] message [secret]".format(sys.argv[0]), file=sys.stderr)
    elif sys.argv[1] == "encode":
        print(encode(sys.argv[2], sys.argv[3]))
    elif sys.argv[1] == "decode":
        print(decode(sys.argv[2]))