Fix Base58 encoding/decoding

Author: Vaibhav-Sawate

ciphers/base58.py

@@ -0,0 +1,60 @@
+BASE58_ALPHABET = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz"
+
+
+def base58_encode(data: bytes) -> str:
+    """Encodes data in Base58.
+
+    Args:
+        data (bytes): Data to be encoded.
+
+    Returns:
+        str: Base58 encoded string.
+    """
+    num = int.from_bytes(data, "big")
+    encoded = ""
+    while num > 0:
+        num, rem = divmod(num, 58)
+        encoded = BASE58_ALPHABET[rem] + encoded
+
+    # Add '1' for each leading 0 byte
+    n = 0
+    for byte in data:
+        if byte == 0:
+            n += 1
+        else:
+            break
+    return "1" * n + encoded
+
+
+def base58_decode(s: str) -> bytes:
+    """Decodes Base58 encoded string back to bytes.
+
+    Args:
+        s (str): Base58 encoded string.
+
+    Returns:
+        bytes: Decoded data.
+
+    Raises:
+        ValueError: If the string contains invalid Base58 characters.
+    """
+    num = 0
+    for char in s:
+        if char not in BASE58_ALPHABET:
+            error_message = f"Invalid character '{char}' in Base58 string"
+            raise ValueError(error_message)
+        num *= 58
+        num += BASE58_ALPHABET.index(char)
+
+    # Convert the number to bytes
+    combined = num.to_bytes((num.bit_length() + 7) // 8, "big")
+
+    # Add leading zeros
+    num_leading_zeros = len(s) - len(s.lstrip("1"))
+    return b"\x00" * num_leading_zeros + combined
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()