[Bitcoin-development] BIP 38 NFC normalisation issue

Aaron Voisine voisine at gmail.com
Wed Jul 16 21:06:41 UTC 2014


If I first remove \u0000, so the non-normalized passphrase is
"\u03D2\u0301\U00010400\U0001F4A9", and then NFC normalize it, it
becomes "\u03D3\U00010400\U0001F4A9"

UTF-8 encoded this is: 0xcf93f0909080f09f92a9 (not the same as what
you got, Andreas!)

Encoding private key: 5Jajm8eQ22H3pGWLEVCXyvND8dQZhiQhoLJNKjYXk9roUFTMSZ4
with this passphrase, I get a BIP38 key of:
6PRW5o9FMb4hAYRQPmgcvVDTyDtr6R17VMXGLmvKjKVpGkYhBJ4uYuR9wZ

I recommend rather than simply removing control characters from the
password that instead the spec require that passwords containing
control characters are invalid. We don't want people trying to be
clever and putting them in thinking they are adding to the password
entropy.

Also for UI compatibility across many platforms, I'm also in favor
disallowing any character below U+0020 (space)

I can submit a PR once we figure out why Andreas's passphrase was
different than what I got.

Aaron Voisine
breadwallet.com


On Wed, Jul 16, 2014 at 4:04 AM, Andreas Schildbach
<andreas at schildbach.de> wrote:
> Damn, I just realized that I implement only the decoding side of BIP38.
> So I cannot propose a complete test vector. Here is what I have:
>
>
> Passphrase: ϓ␀𐐀💩 (\u03D2\u0301\u0000\U00010400\U0001F4A9; GREEK
> UPSILON WITH HOOK, COMBINING ACUTE ACCENT, NULL, DESERET CAPITAL LETTER
> LONG I, PILE OF POO)
>
> Passphrase bytes after removing ISO control characters and NFC
> normalization: 0xcf933034303066346139
>
> Bitcoin Address: 16ktGzmfrurhbhi6JGqsMWf7TyqK9HNAeF
>
> Unencrypted private key (WIF):
> 5Jajm8eQ22H3pGWLEVCXyvND8dQZhiQhoLJNKjYXk9roUFTMSZ4
>
>
> Can someone calculate the encrypted key from it (using whatever
> implementation) and I will verify it decodes properly in bitcoinj?
>
>
>
> On 07/16/2014 12:46 PM, Andreas Schildbach wrote:
>> I will change the bitcoinj implementation and propose a new test vector.
>>
>>
>>
>> On 07/16/2014 11:29 AM, Mike Hearn wrote:
>>> Yes sorry, you're right, the issue starts with the null code point.
>>> Python seems to have problems starting there too. It might work if we
>>> took that out.
>>>
>>>
>>> On Wed, Jul 16, 2014 at 11:17 AM, Andreas Schildbach
>>> <andreas at schildbach.de <mailto:andreas at schildbach.de>> wrote:
>>>
>>>     Guys, you are always talking about the Unicode astral plane, but in fact
>>>     its a plain old (ASCII) control character where this problem starts and
>>>     likely ends: \u0000.
>>>
>>>     Let's ban/filter ISO control characters and be done with it. Most
>>>     control characters will never be enterable by any keyboard into a
>>>     password field. Of course I assume that Character.isISOControl() works
>>>     consistently across platforms.
>>>
>>>     http://docs.oracle.com/javase/7/docs/api/java/lang/Character.html#isISOControl%28char%29
>>>
>>>
>>>     On 07/16/2014 12:23 AM, Aaron Voisine wrote:
>>>     > If the user creates a password on an iOS device with an astral
>>>     > character and then can't enter that password on a JVM wallet, that
>>>     > sucks. If JVMs really can't support unicode NFC then that's a strong
>>>     > case to limit the spec to the subset of unicode that all popular
>>>     > platforms can support, but it sounds like it might just be a JVM
>>>     > string library bug that could hopefully be reported and fixed. I get
>>>     > the same result as in the test case using apple's
>>>     > CFStringNormalize(passphrase, kCFStringNormalizationFormC);
>>>     >
>>>     > Aaron Voisine
>>>     > breadwallet.com <http://breadwallet.com>
>>>     >
>>>     >
>>>     > On Tue, Jul 15, 2014 at 11:20 AM, Mike Hearn <mike at plan99.net
>>>     <mailto:mike at plan99.net>> wrote:
>>>     >> Yes, we know, Andreas' code is indeed doing normalisation.
>>>     >>
>>>     >> However it appears the output bytes end up being different. What
>>>     I get back
>>>     >> is:
>>>     >>
>>>     >> cf930001303430300166346139
>>>     >>
>>>     >> vs
>>>     >>
>>>     >> cf9300f0909080f09f92a9
>>>     >>
>>>     >> from the spec.
>>>     >>
>>>     >> I'm not sure why. It appears this is due to the character from
>>>     the astral
>>>     >> planes. Java is old and uses 16 bit characters internally - it
>>>     wouldn't
>>>     >> surprise me if there's some weirdness that means it doesn't/won't
>>>     support
>>>     >> this kind of thing.
>>>     >>
>>>     >> I recommend instead that any implementation that wishes to be
>>>     compatible
>>>     >> with JVM based wallets (I suspect Android is the same) just
>>>     refuse any
>>>     >> passphrase that includes characters outside the BMP. At least
>>>     unless someone
>>>     >> can find a fix. I somehow doubt this will really hurt anyone.
>>>     >>
>>>     >>
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>>
>>
>>
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>>
>
>
>
> ------------------------------------------------------------------------------
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> search up to 200,000 lines of code with a free copy of Black Duck
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> http://p.sf.net/sfu/bds
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