The bold values are the witness program lengths and address lengths of the segwit v0 programs (BIP-141), which clearly need to be covered in my proposed amendment. 32 bytes is also the proposed witness program length for segwit v1 that would correspond to a taproot (BIP-341) program.
On Wed, Jul 15, 2020 at 5:05 PM Greg Sanders <gsander...@gmail.com> wrote: > Can you make it clear what the bold vs not-bold numbers mean? > > On Wed, Jul 15, 2020 at 4:56 PM Russell O'Connor via bitcoin-dev < > bitcoin-dev@lists.linuxfoundation.org> wrote: > >> On Wed, Nov 13, 2019 at 1:31 AM Pieter Wuille via bitcoin-dev < >> bitcoin-dev@lists.linuxfoundation.org> wrote: >> >>> >>> That brings me to Matt's point: there is no need to do this right now. >>> We can simply amend BIP173 to only permit length 20 and length 32 (and only >>> length 20 for v0, if you like; but they're so far apart that permitting >>> both shouldn't hurt), for now. Introducing the "new" address format (the >>> one using an improved checksum algorithm) only needs to be there in time >>> for when a non-32-byte-witness-program would come in sight. >>> >> >> As a prerequisite to taproot activation, I was looking into amending >> BIP173 as stated above. However after reviewing >> https://gist.github.com/sipa/a9845b37c1b298a7301c33a04090b2eb#detection-of-insertion-errors >> it seems that insertions of 5 characters or more is "safe" in the sense >> that there is low probability of creating a valid checksum by doing so >> randomly. >> >> This means we could safely allow witness programs of lengths *20*, 23, >> 26, 29, *32*, 36, and 40 (or 39). These correspond to Bech32 addresses >> of length *42*, 47, 52, 57, *62*, 68, and 74 (or 73). We could also >> support a set of shorter addresses, but given the lack of entropy in such >> short addresses, it is hard to believe that such witness programs could be >> used to secure anything. I'm not sure what the motivation for allowing >> such short witness programs was, but I'm somewhat inclined to exclude them >> from the segwit address format. >> >> Given that we would only be able to support one of 39 or 40 byte witness >> programs, it is sensible to choose to allow 40 byte witness programs to be >> addressable. This is the maximum witness program size allowed by BIP 141. >> >> So my proposal would be to amend BIP173 in such a way to restrict "bc" >> and "tb" segwit address formats to require witness programs be of size >> *20*, 23, 26, 29, *32*, 36, or 40. Witness programs of other sizes >> (between 2 and 40) would, of course, still be legal in accordance with BIP >> 141; however they would be unaddressable by using this "bc" and "tb" >> prefix. Another address format would be needed to support other witness >> sizes, should the need ever arise. >> >> -- >> Russell O'Connor >> _______________________________________________ >> bitcoin-dev mailing list >> bitcoin-dev@lists.linuxfoundation.org >> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev >> >
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