initial upload

dracondi.py

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+#!/usr/bin/env python3
+
+# DRACONDI: Dual-key Rotating Alphabet CONDI
+
+import sys, re
+from collections import OrderedDict
+from random import randint, choice
+from string import ascii_lowercase
+
+def prepmsg(s:str):
+    return re.sub(r'[^a-z]', '', s.lower())
+
+def dracondi_key(keyphrase:str):
+    prekey = ''
+    oa = ord('a')
+    for c in prepmsg(keyphrase):
+        while prekey.find(c) != -1 and len(prekey) < 26:
+            c = chr(oa + ((25 + ord(c) - oa) % 26))
+        prekey += c
+    offs = len(prekey) % 26
+    alpha = prekey + ''.join(ascii_lowercase)
+    unshifted = ''.join(list(OrderedDict.fromkeys(alpha).keys()))
+    return (unshifted + unshifted)[offs:offs+26]
+
+def dracondi_enc(msg:str, ka1:str, ka2:str):
+    offs = randint(0, 25)
+    res = ka1[offs]
+    for i,c in enumerate(prepmsg(msg)):
+        rc = ka1[(ka1.index(c) + offs) % 26]
+        res += rc
+        offs = (ka2.index(rc) + i + 1) % 26
+    l = len(res) % 5
+    if l > 0:
+        res += ''.join([choice(ascii_lowercase) for i in range(0, 5 - l)])
+    return ' '.join([res[i:i+5] for i in range(0, len(res), 5)])
+
+def dracondi_dec(msg:str, ka1:str, ka2:str):
+    res = ''
+    msg = prepmsg(msg)
+    offs = ka1.index(msg[0])
+    for i,c in enumerate(msg[1:]):
+        res += ka1[(26 + ka1.index(c) - offs) % 26]
+        offs = (ka2.index(c) + i + 1) % 26
+    return res
+
+# entrypoint parameters: [mode] [key1] [key2]
+# modes: e - encrypt, d - decrypt, k - print out keyed alphabets
+def main():
+    mode = sys.argv[1].lower()
+    kp1 = sys.argv[2]
+    kp2 = sys.argv[3]
+    ka1 = dracondi_key(kp1)
+    ka2 = dracondi_key(kp2)
+    if mode.startswith('e'):
+        msg = sys.stdin.read()
+        print(dracondi_enc(msg, ka1, ka2))
+    elif mode.startswith('k'):
+        print('Keyed alphabet 1:', ka1)
+        print('Keyed alphabet 2:', ka2)
+    else:
+        msg = sys.stdin.read()
+        print(dracondi_dec(msg, ka1, ka2))
+
+if __name__ == '__main__':
+    main()