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From: Praveen Baratam <praveen.baratam@gmail.com>
Date: Mon, 20 Nov 2017 23:37:40 +0530
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To: Johnson Lau <jl2012@xbt.hk>
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Subject: Re: [bitcoin-dev] Why SegWit Anyway?
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BIP 140 looks like it solves Tx Malleability with least impact on current
practices. It is still a soft fork though.
Finally, if we were to create an alternative cyptocurrency similar to
Bitcoin, a Normalized Tx ID approach would be a better choice if I get it
right!
=E1=90=A7
On Mon, Nov 20, 2017 at 11:15 PM, Johnson Lau <jl2012@xbt.hk> wrote:
> We can=E2=80=99t =E2=80=9Cjust compute the Transaction ID the same way th=
e hash for
> signing the transaction is computed=E2=80=9D because with different SIGHA=
SH flags,
> there are 6 (actually 256) ways to hash a transaction.
>
> Also, changing the definition of TxID is a hardfork change, i.e. everyone
> are required to upgrade or a chain split will happen.
>
> It is possible to use =E2=80=9Cnormalised TxID=E2=80=9D (BIP140) to fix m=
alleability
> issue. As a softfork, BIP140 doesn=E2=80=99t change the definition of TxI=
D.
> Instead, the normalised txid (i.e. txid with scriptSig removed) is used
> when making signature. Comparing with segwit (BIP141), BIP140 does not ha=
ve
> the side-effect of block size increase, and doesn=E2=80=99t provide any i=
ncentive
> to control the size of UTXO set. Also, BIP140 makes the UTXO set
> permanently bigger, as the database needs to store both txid and normalis=
ed
> txid
>
> On 21 Nov 2017, at 1:24 AM, Praveen Baratam via bitcoin-dev <
> bitcoin-dev@lists.linuxfoundation.org> wrote:
>
> Bitcoin Noob here. Please forgive my ignorance.
>
> From what I understand, in SegWit, the transaction needs to be serialized
> into a data structure that is different from the current one where
> signatures are separated from the rest of the transaction data.
>
> Why change the format at all? Why cant we just compute the Transaction ID
> the same way the hash for signing the transaction is computed?
>
> --
> Dr. Praveen Baratam
>
> about.me <http://about.me/praveen.baratam>
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev@lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>
>
>
--=20
Dr. Praveen Baratam
about.me <http://about.me/praveen.baratam>
--001a11469a608cb48a055e6df75f
Content-Type: text/html; charset="UTF-8"
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<div dir=3D"ltr">BIP 140 looks like it solves Tx Malleability with least im=
pact on current practices. It is still a soft fork though.<div><br></div><d=
iv>Finally, if we were to create an alternative cyptocurrency similar to Bi=
tcoin, a Normalized Tx ID approach would be a better choice if I get it rig=
ht!</div></div><div hspace=3D"streak-pt-mark" style=3D"max-height:1px"><img=
alt=3D"" style=3D"width:0px;max-height:0px;overflow:hidden" src=3D"https:/=
/mailfoogae.appspot.com/t?sender=3DacHJhdmVlbi5iYXJhdGFtQGdtYWlsLmNvbQ%3D%3=
D&type=3Dzerocontent&guid=3D1dc0cb1a-dc60-4b69-828a-6db933a55c26"><=
font color=3D"#ffffff" size=3D"1">=E1=90=A7</font></div><div class=3D"gmail=
_extra"><br><div class=3D"gmail_quote">On Mon, Nov 20, 2017 at 11:15 PM, Jo=
hnson Lau <span dir=3D"ltr"><<a href=3D"mailto:jl2012@xbt.hk" target=3D"=
_blank">jl2012@xbt.hk</a>></span> wrote:<br><blockquote class=3D"gmail_q=
uote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1e=
x"><div style=3D"word-wrap:break-word;line-break:after-white-space"><div>We=
can=E2=80=99t =E2=80=9Cjust compute the Transaction ID the same way the ha=
sh for signing the transaction is computed=E2=80=9D because with different =
SIGHASH flags, there are 6 (actually 256) ways to hash a transaction.</div>=
<div><br></div><div>Also, changing the definition of TxID is a hardfork cha=
nge, i.e. everyone are required to upgrade or a chain split will happen.</d=
iv><div><br></div>It is possible to use =E2=80=9Cnormalised TxID=E2=80=9D (=
BIP140) to fix malleability issue. As a softfork, BIP140 doesn=E2=80=99t ch=
ange the definition of TxID. Instead, the normalised txid (i.e. txid with s=
criptSig removed) is used when making signature. Comparing with segwit (BIP=
141), BIP140 does not have the side-effect of block size increase, and does=
n=E2=80=99t provide any incentive to control the size of UTXO set. Also, BI=
P140 makes the UTXO set permanently bigger, as the database needs to store =
both txid and normalised txid<br><div><div><br><blockquote type=3D"cite"><d=
iv><div class=3D"h5"><div>On 21 Nov 2017, at 1:24 AM, Praveen Baratam via b=
itcoin-dev <<a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org" tar=
get=3D"_blank">bitcoin-dev@lists.<wbr>linuxfoundation.org</a>> wrote:</d=
iv><br class=3D"m_-4649666739189099192Apple-interchange-newline"></div></di=
v><div><div><div class=3D"h5"><div dir=3D"ltr"><div><span style=3D"font-fam=
ily:Verdana,arial,sans-serif;font-size:14px">Bitcoin Noob here. Please forg=
ive my ignorance.</span></div><span style=3D"font-family:Verdana,arial,sans=
-serif;font-size:14px"><div><span style=3D"font-family:Verdana,arial,sans-s=
erif;font-size:14px"><br></span></div>From what I understand, in SegWit, th=
e transaction needs to be serialized into a data structure that is differen=
t from the current one where signatures are separated from the rest of the =
transaction data.</span><div><span style=3D"font-family:Verdana,arial,sans-=
serif;font-size:14px"><br></span></div><div><span style=3D"font-family:Verd=
ana,arial,sans-serif;font-size:14px">Why change the format at all? Why cant=
we just compute the Transaction ID the same way the hash for signing the t=
ransaction is computed?</span><br clear=3D"all"><div><br></div>-- <br><div =
class=3D"m_-4649666739189099192gmail_signature"><div style=3D"color:rgb(34,=
34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255=
,255,255)">Dr. Praveen Baratam</div><div style=3D"color:rgb(34,34,34);font-=
family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)"><=
br></div><div style=3D"color:rgb(34,34,34);font-family:arial,sans-serif;fon=
t-size:13px;background-color:rgb(255,255,255)"><a href=3D"http://about.me/p=
raveen.baratam" style=3D"color:rgb(17,85,204)" target=3D"_blank">about.me</=
a></div></div>
</div></div></div></div>
______________________________<wbr>_________________<span class=3D""><br>bi=
tcoin-dev mailing list<br><a href=3D"mailto:bitcoin-dev@lists.linuxfoundati=
on.org" target=3D"_blank">bitcoin-dev@lists.<wbr>linuxfoundation.org</a><br=
><a href=3D"https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev"=
target=3D"_blank">https://lists.linuxfoundation.<wbr>org/mailman/listinfo/=
bitcoin-<wbr>dev</a><br></span></div></blockquote></div><br></div></div></b=
lockquote></div><br><br clear=3D"all"><div><br></div>-- <br><div class=3D"g=
mail_signature" data-smartmail=3D"gmail_signature"><div style=3D"color:rgb(=
34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(=
255,255,255)">Dr. Praveen Baratam</div><div style=3D"color:rgb(34,34,34);fo=
nt-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)=
"><br></div><div style=3D"color:rgb(34,34,34);font-family:arial,sans-serif;=
font-size:13px;background-color:rgb(255,255,255)"><a href=3D"http://about.m=
e/praveen.baratam" style=3D"color:rgb(17,85,204)" target=3D"_blank">about.m=
e</a></div></div>
</div>
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