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[73.227.67.43]) by smtp.gmail.com with ESMTPSA id af79cd13be357-7be9af25306sm474650085a.116.2025.01.27.22.42.42 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 27 Jan 2025 22:42:42 -0800 (PST) Content-Type: multipart/alternative; boundary=Apple-Mail-F07DB2B7-3769-479D-BECA-2ECF5634B6C8 Content-Transfer-Encoding: 7bit From: Eric Voskuil Mime-Version: 1.0 (1.0) Subject: Re: [bitcoindev] UTXO checkpoint transactions Date: Tue, 28 Jan 2025 01:42:31 -0500 Message-Id: <96CD2E9E-3EB8-43E2-921E-A8CA99317181@voskuil.org> References: Cc: bitcoindev@googlegroups.com In-Reply-To: To: Erik Aronesty X-Mailer: iPhone Mail (22B91) X-Original-Sender: eric@voskuil.org X-Original-Authentication-Results: gmr-mx.google.com; dkim=pass header.i=@voskuil-org.20230601.gappssmtp.com header.s=20230601 header.b=P40CZPO8; spf=none (google.com: eric@voskuil.org does not designate permitted sender hosts) smtp.mailfrom=eric@voskuil.org; dara=pass header.i=@googlegroups.com Precedence: list Mailing-list: list bitcoindev@googlegroups.com; contact bitcoindev+owners@googlegroups.com List-ID: X-Google-Group-Id: 786775582512 List-Post: , List-Help: , List-Archive: , List-Unsubscribe: , X-Spam-Score: 1.6 (+) --Apple-Mail-F07DB2B7-3769-479D-BECA-2ECF5634B6C8 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Hi Erik,

Miners committin= g to a checkpoint does not make the checkpoint valid. The only way one woul= d know it=E2=80=99s valid is by validating the chain up to that point.

Given that it implies one woul= d be trusting hash power for validity there is no need for a utxo set. SPV = is sufficient. A utxo set is only necessary for validation.

e

On Jan 28, 2025, at 01:32, Erik Aronesty <erik@q32.com>= ; wrote:

=EF=BB=BF
Has it been considered to add a UTXO checkpoi= nt transaction 

Here's ho= w it would work 

So= meone submits a transaction that contains a large fee and a hash of the UTX= O set along with block height as opcode parameter 

Miners refuse to include this transaction u= nless the hash of the UTXO set matches 

Because performing that hash is expensive, it should h= ave an extremely high cost factor, equivalent to say a 100KB transaction or= something 

These c= heckpoints are explicitly for the purpose of fast-synchronizing extremely l= ightweight nodes.  It's reasonable to refuse to use a checkpoint that = isn't at least several months old.   It should be easy for anyone= to find a sufficiently aged checkpoint and synchronize from that point onw= ard.


Or is this just a solution without a problem?






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