Re: [Bitcoin-development] BIP 38 NFC normalisation issue

[Andreas Schildbach <andreas@schildbach.de>]

Please excuse me. I had a more thorough look at the original problem and
found that the only problem with the original test case was that you
cannot specify codepoints from the SMP using \u in Java. I always tried
\u010400 but that doesn't work.

Here is a fix for bitcoinj. The test now passes.

https://github.com/bitcoinj/bitcoinj/pull/143

We can (and probably should) still need to filter control chars, I'll
have a look at that now again.


On 07/16/2014 11:06 PM, Aaron Voisine wrote:
> 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@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@schildbach.de <mailto:andreas@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@plan99.net
>>>>     <mailto:mike@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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