[Bitcoin-development] BIP 38 NFC normalisation issue

Eric Winer enwiner at gmail.com
Tue Jul 15 13:07:47 UTC 2014

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

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> 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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