NISTTV_BASE62

Author: bschoening

ff3/ff3.py

@@ -76,18 +76,16 @@ class FF3Cipher:
     from the base 62 alphabet (digits + lowercase + uppercase latin) are used.
     """
     DOMAIN_MIN = 1_000_000  # 1M required in FF3-1
-    BASE62 = string.digits + string.ascii_lowercase + string.ascii_uppercase
+    BASE62 = string.digits + string.ascii_uppercase + string.ascii_lowercase
+    NISTTV_BASE62 = string.digits + string.ascii_lowercase + string.ascii_uppercase
     BASE62_LEN = len(BASE62)
     RADIX_MAX = 256  # Support 8-bit alphabets for now
 
-    def __init__(self, key, tweak, radix=10, ):
+    def __init__(self, key : str, tweak : str, alphabet : str ):
         keybytes = bytes.fromhex(key)
         self.tweak = tweak
-        self.radix = radix
-        if radix <= FF3Cipher.BASE62_LEN:
-            self.alphabet = FF3Cipher.BASE62[0:radix]
-        else:
-            self.alphabet = None
+        self.alphabet = alphabet
+        self.radix = len(alphabet)
 
         # Calculate range of supported message lengths [minLen..maxLen]
         # per revised spec, radix^minLength >= 1,000,000.
@@ -120,6 +118,13 @@ def __init__(self, key, tweak, radix=10, ):
     # factory method to create a FF3Cipher object with a custom alphabet
     @staticmethod
     def withCustomAlphabet(key, tweak, alphabet):
+        c = FF3Cipher(key, tweak, alphabet)
+        return c
+
+    # factory method to create a FF3Cipher object with a radix
+    @staticmethod
+    def withRadix(key, tweak, radix):
+        alphabet = FF3Cipher.BASE62[0:radix]
         c = FF3Cipher(key, tweak, len(alphabet))
         c.alphabet = alphabet
         return c

ff3/ff3_test.py

@@ -373,14 +373,16 @@ def test_encrypt_boundaries(self):
     def test_encrypt_all(self):
         for test in testVectors:
             with self.subTest(testVector=test):
-                c = FF3Cipher(test['key'], test['tweak'], test['radix'])
+                alphabet = FF3Cipher.NISTTV_BASE62[0:test['radix']]
+                c = FF3Cipher(test['key'], test['tweak'], alphabet)
                 s = c.encrypt(test['plaintext'])
                 self.assertEqual(s, test['ciphertext'])
 
     def test_decrypt_all(self):
         for test in testVectors:
             with self.subTest(testVector=test):
-                c = FF3Cipher(test['key'], test['tweak'], test['radix'])
+                alphabet = FF3Cipher.NISTTV_BASE62[0:test['radix']]
+                c = FF3Cipher(test['key'], test['tweak'], alphabet)
                 s = c.decrypt(test['ciphertext'])
                 self.assertEqual(s, test['plaintext'])
 
@@ -419,7 +421,7 @@ def test_custom_alphabet(self):
         tweak = "D8E7920AFA330A73"
         plaintext = "⁸⁹⁰¹²¹²³⁴⁵⁶⁷⁸⁹⁰⁰⁰⁰"
         ciphertext = "⁷⁵⁰⁹¹⁸⁸¹⁴⁰⁵⁸⁶⁵⁴⁶⁰⁷"
-        c = FF3Cipher.withCustomAlphabet(key, tweak, alphabet)
+        c = FF3Cipher(key, tweak, alphabet)
         s = c.encrypt(plaintext)
         self.assertEqual(s, ciphertext)
         x = c.decrypt(s)
@@ -466,7 +468,7 @@ def test_whole_domain(self):
         tweak = "D8E7920AFA330A73"
         for radix, plaintext_len, alphabet in test_cases:
             if alphabet is None:
-                c = FF3Cipher(key, tweak, radix=radix)
+                c = FF3Cipher.withRadix(key, tweak, radix=radix)
             else:
                 c = FF3Cipher.withCustomAlphabet(key, tweak, alphabet=alphabet)
             self.subTest(radix=radix, plaintext_len=plaintext_len)