[Bitcoin-development] BIP 38 NFC normalisation issue

Tue Jul 15 13:32:01 UTC 2014

I have a python implementation that seems to pass this test vector:

https://github.com/wozz/electrum/blob/bip38_import/lib/bip38.py#L299

On Jul 15, 2014, at 9:19 AM, Andreas Schildbach <andreas at schildbach.de> wrote:

> I think generally control-characters (such as \u0000) should be
> disallowed in passphrases. (Even the use of whitespaces is very
> questionable.)
> 
> I'm ok with allowing pile-of-poo's. On mobile phones there is keyboards
> just containing emoticons -- why not allow those? Assuming NFC works of
> course.
> 
> 
> On 07/15/2014 03:07 PM, Eric Winer wrote:
>> I don't know for sure if the test vector is correct NFC form.  But for
>> what it's worth, the Pile of Poo character is pretty easily accessible
>> on the iPhone and Android keyboards, and in this string it's already in
>> NFC form (f09f92a9 in the test result).  I've certainly seen it in
>> usernames around the internet, and wouldn't be surprised to see it in
>> passphrases entered on smartphones, especially if the author of a
>> BIP38-compatible app includes a (possibly ill-advised) suggestion to
>> have your passphrase "include special characters".
>> 
>> I haven't seen the NULL character on any smartphone keyboards, though -
>> I assume the iOS and Android developers had the foresight to know how
>> much havoc that would wreak on systems assuming null-terminated strings.
>> It seems unlikely that NULL would be in a real-world passphrase entered
>> by a sane user.
>> 
>> 
>> On Tue, Jul 15, 2014 at 8:03 AM, Mike Hearn <mike at plan99.net
>> <mailto:mike at plan99.net>> wrote:
>> 
>>    [+cc aaron]
>> 
>>    We recently added an implementation of BIP 38 (password protected
>>    private keys) to bitcoinj. It came to my attention that the third
>>    test vector may be broken. It gives a hex version of what the NFC
>>    normalised version of the input string should be, but this does not
>>    match the results of the Java unicode normaliser, and in fact I
>>    can't even get Python to print the names of the characters past the
>>    embedded null. I'm curious where this normalised version came from.
>> 
>>    Given that "pile of poo" is not a character I think any sane user
>>    would put into a passphrase, I question the value of this test
>>    vector. NFC form is intended to collapse things like umlaut control
>>    characters onto their prior code point, but here we're feeding the
>>    algorithm what is basically garbage so I'm not totally surprised
>>    that different implementations appear to disagree on the outcome.
>> 
>>    Proposed action: we remove this test vector as it does not represent
>>    any real world usage of the spec, or if we desperately need to
>>    verify NFC normalisation I suggest using a different, more realistic
>>    test string, like Zürich, or something written in Thai.
>> 
>> 
>> 
>>    Test 3:
>> 
>>      * Passphrase ϓ␀𐐀💩 (\u03D2\u0301\u0000\U00010400\U0001F4A9; GREEK
>>        UPSILON WITH HOOK <http://codepoints.net/U+03D2>, COMBINING
>>        ACUTE ACCENT <http://codepoints.net/U+0301>, NULL
>>        <http://codepoints.net/U+0000>, DESERET CAPITAL LETTER LONG I
>>        <http://codepoints.net/U+10400>, PILE OF POO
>>        <http://codepoints.net/U+1F4A9>)
>>      * Encrypted key:
>>        6PRW5o9FLp4gJDDVqJQKJFTpMvdsSGJxMYHtHaQBF3ooa8mwD69bapcDQn
>>      * Bitcoin Address: 16ktGzmfrurhbhi6JGqsMWf7TyqK9HNAeF
>>      * Unencrypted private key (WIF):
>>        5Jajm8eQ22H3pGWLEVCXyvND8dQZhiQhoLJNKjYXk9roUFTMSZ4
>>      * /Note:/ The non-standard UTF-8 characters in this passphrase
>>        should be NFC normalized to result in a passphrase
>>        of0xcf9300f0909080f09f92a9 before further processing
>> 
>> 
>> 
>> 
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> 
> 
> 
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