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To: Clark Moody <clark@clarkmoody.com>,
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Subject: Re: [bitcoin-dev] Bech32 weakness and impact on bip-taproot
addresses
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Good morning all,
It seems to me that adding the length for checksumming purposes need not re=
quire the length to be *actually* added in the address format.
So, currently, below is my understanding of bech32 validation:
* Run BCH checksum on witness program.
* Compare checksum to checksum in address.
* If the checksum matches:
* If version is 0, validate that the witness program is length 20 or 32=
.
* Else accept.
* If the checksum does not match:
* Reject
Let me propose then:
* Run BCH checksum on witness program.
* Compare checksum to checksum in address.
* If the checksum matches:
* If version is 0, validate that the witness program is length 20 or 32=
.
* Else validate that the witness program is length 32.
* If the checksum does not match:
* Get the length of the witness program.
* Prepend the length to the witness program.
* Run BCH checksum on concatenated length | witness program.
* Compare checksum to checksum in address.
* If the checksum matches:
* Accept.
* Else reject.
A writer of bech32 addresses would then:
* If the witness program is length 32, or witness version is 0 and witness =
program length is 20, use a non-length-prefixed checksum.
* Otherwise, use a length-prefixed checksum (but not include the length in =
the address, just change the BCH checksum).
This has the following properties:
* The bech32 address format is retained, and no explicit length is added.
* There are now two checksum formats: one with just the witness program, th=
e other which validates with the witness program length.
* Readers that do not understand the new checksum format will simply reje=
ct them without mis-sending to the wrong witness program.
Is the above acceptable?
Regards,
ZmnSCPxj
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