A BIP proposal for segwit addresses

A BIP proposal for segwit addresses
2017-03-21 16:16 ` Andreas Schildbach
  2017-05-07 21:39 ` Pieter Wuille
  
From: Pieter Wuille @ 2017-03-20 21:35 UTC (permalink / raw)
  To: Bitcoin Dev

Hello everyone,

I'd like to propose a new BIP for native segwit addresses to replace
BIP 142. These addresses are not required for segwit, but are more
efficient, flexible, and nicer to use.

The format is base 32 and uses a simple checksum algorithm with strong
error detection properties. Reference code in several languages as
well as a website demonstrating it are included.

You can find the text here:
https://github.com/sipa/bech32/blob/master/bip-witaddr.mediawiki

Cheers,

-- 
Pieter


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2017-03-20 21:35 [bitcoin-dev] A BIP proposal for segwit addresses Pieter Wuille

  2017-03-21 19:14   ` Peter Todd
  2017-05-07 21:39 ` Pieter Wuille
  
From: Andreas Schildbach @ 2017-03-21 16:16 UTC (permalink / raw)
  To: bitcoin-dev

Why use Base 32 when the QR code alphanumeric mode allows 44 characters?
In Bitcoin Wallet, I use Base 43 (alphabet:
"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ$*+-./:") for most efficient QR
code encoding. I only leave out the space character because it gets
replaced by "+" in URLs.


On 03/20/2017 10:35 PM, Pieter Wuille via bitcoin-dev wrote:
> Hello everyone,
> 
> I'd like to propose a new BIP for native segwit addresses to replace
> BIP 142. These addresses are not required for segwit, but are more
> efficient, flexible, and nicer to use.
> 
> The format is base 32 and uses a simple checksum algorithm with strong
> error detection properties. Reference code in several languages as
> well as a website demonstrating it are included.
> 
> You can find the text here:
> https://github.com/sipa/bech32/blob/master/bip-witaddr.mediawiki
> 
> Cheers,
> 




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2017-03-21 16:16 ` Andreas Schildbach

  2017-03-29 10:07     ` Andreas Schildbach
  
From: Peter Todd @ 2017-03-21 19:14 UTC (permalink / raw)
  To: Andreas Schildbach, Bitcoin Protocol Discussion

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On Tue, Mar 21, 2017 at 05:16:30PM +0100, Andreas Schildbach via bitcoin-dev wrote:
> Why use Base 32 when the QR code alphanumeric mode allows 44 characters?
> In Bitcoin Wallet, I use Base 43 (alphabet:
> "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ$*+-./:") for most efficient QR
> code encoding. I only leave out the space character because it gets
> replaced by "+" in URLs.

Doing that only makes addresses a few % shorter, at the cost of significant
downsides.  For example, not everyone knows what those additional characters
are called, particularly for non-English-speaking users. Non-alphanumeric
characters also complicate using the addresses in a variety of contexts ('/'
in particularly isn't valid in filenames).

I'd suggest you review the "Rational" section of the BIP for more details:

https://github.com/sipa/bech32/blob/master/bip-witaddr.mediawiki#rationale

-- 
https://petertodd.org 'peter'[:-1]@petertodd.org

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2017-03-21 19:14   ` Peter Todd

  2017-03-30  4:50       ` Lucas Ontivero
  
From: Andreas Schildbach @ 2017-03-29 10:07 UTC (permalink / raw)
  To: bitcoin-dev

On 03/21/2017 08:14 PM, Peter Todd via bitcoin-dev wrote:
> On Tue, Mar 21, 2017 at 05:16:30PM +0100, Andreas Schildbach via bitcoin-dev wrote:
>> Why use Base 32 when the QR code alphanumeric mode allows 44 characters?
>> In Bitcoin Wallet, I use Base 43 (alphabet:
>> "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ$*+-./:") for most efficient QR
>> code encoding. I only leave out the space character because it gets
>> replaced by "+" in URLs.
> 
> Doing that only makes addresses a few % shorter, at the cost of significant
> downsides.  For example, not everyone knows what those additional characters
> are called, particularly for non-English-speaking users. Non-alphanumeric
> characters also complicate using the addresses in a variety of contexts ('/'
> in particularly isn't valid in filenames).

I'm not convinced that transmitting addresses via voice should be a
usecase to target at. I don't understand your comment about non-english
speaking users. Obviously they cannot voice-communicate at all with
only-english-speaking users, so there is no need to communicate
voice-communicate addresses between them.

Addresses in QR codes, addresses in URLs and addresses in NFC NDEF
messages are the three most used forms.

Speaking of URLs, actually Base 32 (as well as Base 43) makes QR codes
*bigger* because due to the characters used for URL parameters (?&=)
those QR codes are locked to binary mode. To make them shorter, we'd
need to use something like "Base 64url" (or ideally Base 94 -- all
printable ASCII characters).




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2017-03-29 10:07     ` Andreas Schildbach

  
From: Lucas Ontivero @ 2017-03-30  4:50 UTC (permalink / raw)
  To: Andreas Schildbach, Bitcoin Protocol Discussion

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I don't know if i should response to this mail list or make a comment in
commit file (
https://github.com/sipa/bech32/commit/52b5a0fa6d3174c4150393fb7d6b58d34b4f5e0b#diff-d23a42e5c904045098e8f8b1189f481e
)

* Motivation:

Here I think it could worth to mention that 58 requires mathematical
operations over big numbers. This is not very fast and most of the
programming languages don't provide support for big numbers OOB.

* Why not make an address format that is generic for all scriptPubKeys?:

I understand that if a new generic encoding format is introduced that could
lead to some confusions but what if in the future there is a new type of
address that can also be encoded with bech32? Don't we need a address type
anyway?

thx


2017-03-29 7:07 GMT-03:00 Andreas Schildbach via bitcoin-dev <
bitcoin-dev@lists•linuxfoundation.org>:

> On 03/21/2017 08:14 PM, Peter Todd via bitcoin-dev wrote:
> > On Tue, Mar 21, 2017 at 05:16:30PM +0100, Andreas Schildbach via
> bitcoin-dev wrote:
> >> Why use Base 32 when the QR code alphanumeric mode allows 44 characters?
> >> In Bitcoin Wallet, I use Base 43 (alphabet:
> >> "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ$*+-./:") for most efficient QR
> >> code encoding. I only leave out the space character because it gets
> >> replaced by "+" in URLs.
> >
> > Doing that only makes addresses a few % shorter, at the cost of
> significant
> > downsides.  For example, not everyone knows what those additional
> characters
> > are called, particularly for non-English-speaking users. Non-alphanumeric
> > characters also complicate using the addresses in a variety of contexts
> ('/'
> > in particularly isn't valid in filenames).
>
> I'm not convinced that transmitting addresses via voice should be a
> usecase to target at. I don't understand your comment about non-english
> speaking users. Obviously they cannot voice-communicate at all with
> only-english-speaking users, so there is no need to communicate
> voice-communicate addresses between them.
>
> Addresses in QR codes, addresses in URLs and addresses in NFC NDEF
> messages are the three most used forms.
>
> Speaking of URLs, actually Base 32 (as well as Base 43) makes QR codes
> *bigger* because due to the characters used for URL parameters (?&=)
> those QR codes are locked to binary mode. To make them shorter, we'd
> need to use something like "Base 64url" (or ideally Base 94 -- all
> printable ASCII characters).
>
>
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev@lists•linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>

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2017-03-20 21:35 [bitcoin-dev] A BIP proposal for segwit addresses Pieter Wuille
  2017-03-21 16:16 ` Andreas Schildbach

  2017-05-07 22:34   ` Peter Todd
  2017-05-20 20:13   ` Pieter Wuille
  
From: Pieter Wuille @ 2017-05-07 21:39 UTC (permalink / raw)
  To: Bitcoin Dev

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On Mon, Mar 20, 2017 at 2:35 PM, Pieter Wuille <pieter.wuille@gmail•com>
wrote:

> Hello everyone,
>
> You can find the text here:
> https://github.com/sipa/bech32/blob/master/bip-witaddr.mediawiki
>

Responding to a few comments:

By Andreas Schildbach:

> I'm not convinced that transmitting addresses via voice should be a
usecase to target at

I think it should be. It's certainly not the most important way through
which addresses are communicated or verified, but I am trying to address
all places where humans interact with addresses. I have certainly tried to
verify addresses a few times through voice, when dealing with significant
amounts.

Regarding your QR code comments: it is certainly possible to find a more
compact QR code representation. That is not the goal of the BIP though -
it's trying to introduce one commonly recognizable format that has good
properties for all use cases, even if that means being suboptimal in
certain aspects for some.

> I don't understand your comment about non-english speaking users.
Obviously they cannot voice-communicate at all with only-english-speaking
users, so there is no need to communicate voice-communicate addresses
between them.

I assume that Peter Todd is talking about cases where English speakers are
interacting with non-native English speakers, who may know how to pronounce
numbers or alphabetical characters, but not all special characters.

> Speaking of URLs, actually Base 32 (as well as Base 43) makes QR codes
*bigger* because due to the characters used for URL parameters (?&=) those
QR codes are locked to binary mode.

I believe that is incorrect. Data in QR codes can switch from one mode to
another on a per-character basis (with an overhead of a few bits). I don't
know to what extent common QR encoders make intelligent decisions about
this, but it does not seem very hard.

By Lucas Ontivero:

> Here I think it could worth to mention that 58 requires mathematical
operations over big numbers. This is not very fast and most of the
programming languages don't provide support for big numbers OOB.

It's not that hard to emulate the bignum logic in languages that don't
support it. See for example this code in Bitcoin Core:
https://github.com/bitcoin/bitcoin/blob/v0.14.1/src/base58.cpp#L37L53. So I
think it's not necessary to go into all the possible ways Base58 can be
implemented in the document, and the existing language ("Base58 decoding is
complicated and relatively slow.") is sufficient.

> I understand that if a new generic encoding format is introduced that
could lead to some confusions but what if in the future there is a new type
of address that can also be encoded with bech32? Don't we need a address
type anyway?

I believe that it's likely that new types of outputs that may be introduced
in the future will most likely not be a simple constant byte sequence that
can be computed directly from addresses, but need some processing by the
sender. This is the case for example for Reusable/Stealth addresses and
Confidential Transactions addresses. Such outputs, if ever introduced on a
wide scale, should ideally not be representable as existing address types,
as that could not only lead to confusion, but also to lost privacy and
funds.

And, If there ever is a need for introducing a "constant scriptPubKey" type
address again, the encoding proposed in this document can be reused.
Currently, the header value can be at most 17. In the future new proposals
could give a meaning to values 18 through 31.


In general:

In the past weeks people have contributed two new reference implementations
(Haskell and Rust), and a C++ and Go one are underway (see
https://github.com/sipa/bech32).

I'd like to move forward and request a BIP number assignment for this
proposal.


Cheers,

-- 
Pieter

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2017-05-07 21:39 ` Pieter Wuille

  2017-05-20 20:13   ` Pieter Wuille
  
From: Peter Todd @ 2017-05-07 22:34 UTC (permalink / raw)
  To: Pieter Wuille;  Bitcoin Dev

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On Sun, May 07, 2017 at 02:39:14PM -0700, Pieter Wuille via bitcoin-dev wrote:
> > I don't understand your comment about non-english speaking users.
> Obviously they cannot voice-communicate at all with only-english-speaking
> users, so there is no need to communicate voice-communicate addresses
> between them.
> 
> I assume that Peter Todd is talking about cases where English speakers are
> interacting with non-native English speakers, who may know how to pronounce
> numbers or alphabetical characters, but not all special characters.

Exactly - knowledge of the English language isn't a binary. Equally, I don't
remember ever learning names of special characters in French class back in
elementary school, but I do recall us drilling the alphabet and especially
numbers repeatedly.

If I were trying to tell a French speaker a BTC address, I'd probably be able
to succesfully do it with bech32, but not with any encoding using special
characters.

> In general:
> 
> In the past weeks people have contributed two new reference implementations
> (Haskell and Rust), and a C++ and Go one are underway (see
> https://github.com/sipa/bech32).

FWIW, I also did a partial rust implementation of just the Bech32 encoding for
a prototype non-BTC use-case. Other than the version number being it's own
"chunk" I found it very straight-forward to implement and I think it'll make
for a nice replacement for what otherwise would have been hex digests.

-- 
https://petertodd.org 'peter'[:-1]@petertodd.org

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2017-05-07 21:39 ` Pieter Wuille
  2017-05-07 22:34   ` Peter Todd

  2018-07-26 13:43     ` Russell O'Connor
  
From: Pieter Wuille @ 2017-05-20 20:13 UTC (permalink / raw)
  To: Bitcoin Dev

On Sun, May 7, 2017 at 2:39 PM, Pieter Wuille <pieter.wuille@gmail•com> wrote:
> I'd like to move forward and request a BIP number assignment for this
> proposal.

The proposal has been submitted as BIP173:
https://github.com/bitcoin/bips/blob/master/bip-0173.mediawiki

Cheers,

-- 
Pieter


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2017-05-20 20:13   ` Pieter Wuille

  2018-07-26 14:31       ` Russell O'Connor
  
From: Russell O'Connor @ 2018-07-26 13:43 UTC (permalink / raw)
  To: Pieter Wuille;  Bitcoin Dev

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Hi Pieter,

> The *human-readable part*, which is intended to convey the type of data,
or anything else that is relevant to the reader. This part MUST contain 1
to 83 US-ASCII characters, with each character having a value in the range
[33-126]. HRP validity may be further restricted by specific applications.

You should also add to this section that the HRP should be lowercase.

Since Bech32 forbids mixed-case and otherwise converts everything to
lowercase, it is good to warn upfront against using uppercase in the HRP.

I know the BIP is marked as final, but this wouldn't be a normative change.

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2018-07-26 13:43     ` Russell O'Connor

  
From: Russell O'Connor @ 2018-07-26 14:31 UTC (permalink / raw)
  To: Pieter Wuille;  Bitcoin Dev

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I think I phrased this badly.

What I mean is that there should be a note that HRP should be specified in
lowercase, or at least mention that uppercase and lowercase HRPs are
considered equivalent and will be canonicalized to lowercase during
validation.

On Thu, Jul 26, 2018 at 9:43 AM, Russell O'Connor <roconnor@blockstream•io>
wrote:

> Hi Pieter,
>
> > The *human-readable part*, which is intended to convey the type of
> data, or anything else that is relevant to the reader. This part MUST
> contain 1 to 83 US-ASCII characters, with each character having a value in
> the range [33-126]. HRP validity may be further restricted by specific
> applications.
>
> You should also add to this section that the HRP should be lowercase.
>
> Since Bech32 forbids mixed-case and otherwise converts everything to
> lowercase, it is good to warn upfront against using uppercase in the HRP.
>
> I know the BIP is marked as final, but this wouldn't be a normative change.
>

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