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From: <jl2012@xbt.hk>
To: "'Tier Nolan'" <tier.nolan@gmail.com>
Cc: bitcoin-dev@lists.linuxfoundation.org
Subject: Re: [bitcoin-dev] BIP CPRKV: Check private key verify
Date: Tue, 19 Apr 2016 03:03:07 +0800	[thread overview]
Message-ID: <00aa01d199a4$f3a41c80$daec5580$@xbt.hk> (raw)
In-Reply-To: <CAE-z3OWjqQ=UgNRXyxJiTzsW6Ze7Ytwz3kK2HYcC7eLy2jKnow@mail.gmail.com>

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I just realize that if we have OP_CAT, OP_CHECKPRIVATEKEYVERIFY (aka OP_CHECKPRIVPUBPAIR) is not needed (and is probably better for privacy)

 

Bob has the prikey-x for pubkey-x. Alice and Bob will agree to a random secret nonce, k. They calculate r, in the same way as signing a transaction.

 

The script is:

 

SIZE <r-length + 1> ADD <0x30> SWAP CAT <0x02|r-length|r> CAT SWAP CAT <pubkey-x> CECHKSIGVERIFY <Bob pubkey hash> CHECKSIG

 

To redeem, Bob has to provide:

 

<Bob sig> <0x02|s-length|s|sighashtype>

 

With k, s and sighash, Alice (and only Alice) can recover the prikey-x with the well-known k-reuse exploit

( https://en.wikipedia.org/wiki/Elliptic_Curve_Digital_Signature_Algorithm )

 

The script will be much cleaner if we remove the DER encoding in the next generation of CHECKSIG

 

The benefit is prikey-x remains a secret among Alice and Bob. If they don’t mind exposing the prikey-x, they could use r = x coordinate of pubkey-x, which means k = prikey-x (https://bitcointalk.org/index.php?topic=291092.0) This would reduce the witness size a little bit as a DUP may be used

 

From: bitcoin-dev-bounces@lists.linuxfoundation.org [mailto:bitcoin-dev-bounces@lists.linuxfoundation.org] On Behalf Of Tier Nolan via bitcoin-dev
Sent: Monday, 29 February, 2016 19:53
Cc: Bitcoin Dev <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] BIP CPRKV: Check private key verify

 

On Mon, Feb 29, 2016 at 10:58 AM, Mats Jerratsch <matsjj@gmail.com <mailto:matsjj@gmail.com> > wrote:

This is actually very useful for LN too, see relevant discussion here

http://lists.linuxfoundation.org/pipermail/bitcoin-dev/2015-November/011827.html

 

Is there much demand for trying to code up a patch to the reference client?  I did a basic one, but it would need tests etc. added.

I think that segregated witness is going to be using up any potential soft-fork slot for the time being anyway.


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      reply	other threads:[~2016-04-18 19:03 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-02-11 20:05 [bitcoin-dev] BIP CPRKV: Check private key verify Tier Nolan
2016-02-11 22:20 ` Thomas Kerin
2016-02-11 23:04   ` Tier Nolan
2016-02-12  5:02 ` jl2012
2016-02-12 10:05   ` Tier Nolan
2016-02-29 10:58     ` Mats Jerratsch
2016-02-29 11:52       ` Tier Nolan
2016-04-18 19:03         ` jl2012 [this message]

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