Polynomial identity check failed in multiRangeProofVerifier

[darioAnongba]

Hi,

I've been testing some values in the multiRangeProofVerifier and I get a Polynomial identity check failed when I tested it with number = 321 and change = 29 (I got rid of extra and zero).

This error appears randomly depending on the inputted values. Any idea why ?

Cheers,
Dario

[shamatar]

Hello Dario. If you use a MultiRangeProof, then the total proof capacity of N bytes is divided evenly between M values, and if any of the values exceeds the 2^(N/M) - 1 value, the proof becomes invalid. Sincerely, Alex

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________________________________ From: Dario Anongba Varela <notifications@github.com> Sent: Monday, July 2, 2018 1:22:58 PM To: BANKEX/BulletproofJS Cc: Subscribed Subject: [BANKEX/BulletproofJS] Polynomial identity check failed in multiRangeProofVerifier (#2) Hi, I've been testing some values in the multiRangeProofVerifier and I get a Polynomial identity check failed when I tested it with number = 321 and change = 29 (I got rid of extra and zero). This error appears randomly depending on the inputted values. Any idea why ? Cheers, Dario — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub<#2>, or mute the thread<https://github.com/notifications/unsubscribe-auth/AGKv94Y18TyliSIXiWhqmG3cDf2pKRPOks5uCfSCgaJpZM4U_DxP>.

[darioAnongba]

Hi Alex,

Thanks for the quick answer!

Indeed it's true that trying the same values with 32 bits does work with 321 and 29.

If I understand correctly and assuming that M is always 2 in my case, with 32 bits, the upper bound is 2^16 = 65'536 and was 2^8 before = 256, so that's why it failed? Because 321 is bigger than 256?

Thanks!

[shamatar]

Yes, MultiRange is not magical, it saves on scalar values, but number of field elements is still log2(fullConcatenatedBitLength). Nevertheless it’s handy in practice, especially if you enforce same length proofs for each of the commitments

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________________________________ From: Dario Anongba Varela <notifications@github.com> Sent: Monday, July 2, 2018 2:43:46 PM To: BANKEX/BulletproofJS Cc: Alexander; Comment Subject: Re: [BANKEX/BulletproofJS] Polynomial identity check failed in multiRangeProofVerifier (#2) Closed #2<#2>. — You are receiving this because you commented. Reply to this email directly, view it on GitHub<#2 (comment)>, or mute the thread<https://github.com/notifications/unsubscribe-auth/AGKv9w_rXCHvoE2bgOD-FtW1wvt1NV6Fks5uCgdygaJpZM4U_DxP>.