Received: from sog-mx-2.v43.ch3.sourceforge.com ([172.29.43.192] helo=mx.sourceforge.net) by sfs-ml-3.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1Wt2KB-0005f9-Jl for bitcoin-development@lists.sourceforge.net; Fri, 06 Jun 2014 22:09:23 +0000 Received-SPF: pass (sog-mx-2.v43.ch3.sourceforge.com: domain of i-rme.es designates 209.85.215.54 as permitted sender) client-ip=209.85.215.54; envelope-from=rme@i-rme.es; helo=mail-la0-f54.google.com; Received: from mail-la0-f54.google.com ([209.85.215.54]) by sog-mx-2.v43.ch3.sourceforge.com with esmtps (TLSv1:RC4-SHA:128) (Exim 4.76) id 1Wt2KA-0003pN-LB for bitcoin-development@lists.sourceforge.net; Fri, 06 Jun 2014 22:09:23 +0000 Received: by mail-la0-f54.google.com with SMTP id pv20so1931603lab.27 for ; Fri, 06 Jun 2014 15:09:15 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:from:date:message-id:subject:cc :content-type; bh=mPzytAXAzVKGZtfSLaTBI+Q+5iO3fOzgO8KrDa/E7n4=; b=cDisiGdmxPu/a6CLgsEnMIoxJBVuwSE8f4MCxNJA4GeuHatWZfSJ+RYWiZZ8neTZKP EIvRI8FQg8sd3ACeiA40ArhpJBxE6KDV1XH/J7lHN97db05eVApsIyzVZK6kstmYCH0q pBUNUdqF/9ZdGHOKHI+y7r0PzwlvIoHgCc3Rhpi6xlHFv2CtK2aL2xHDkK6p5w5hn1Wk H6AhGr9r22kP/12HIeKX1KkATOc1gPZN0BHTUE3y2mKen8ttg3ooeOr4DHTnIx9nZUCg rTZUSFQDBDfxqZgaAIGNqE3Dse2ECFraJToOwtYZnEhrJvQIWtBezhAT+mw95jvBscyf DepA== X-Gm-Message-State: ALoCoQmSzkCpOf59dt2hy1ieaaD2Xs3RiLD9CCQW6fUt9rXbYCEWlmahKN3iQULpngIUdZ9MHR8f X-Received: by 10.112.143.132 with SMTP id se4mr5161677lbb.53.1402092238189; Fri, 06 Jun 2014 15:03:58 -0700 (PDT) MIME-Version: 1.0 Received: by 10.152.199.8 with HTTP; Fri, 6 Jun 2014 15:03:28 -0700 (PDT) X-Originating-IP: [85.251.84.81] From: =?UTF-8?B?UmHDumwgTWFydMOtbmV6?= Date: Sat, 7 Jun 2014 00:03:28 +0200 Message-ID: Cc: Bitcoin Dev Content-Type: multipart/alternative; boundary=089e01227df4cccdcf04fb320948 X-Spam-Score: 0.6 (/) X-Spam-Report: Spam Filtering performed by mx.sourceforge.net. See http://spamassassin.org/tag/ for more details. -1.5 SPF_CHECK_PASS SPF reports sender host as permitted sender for sender-domain -0.0 SPF_PASS SPF: sender matches SPF record 1.2 MISSING_HEADERS Missing To: header 1.0 HTML_MESSAGE BODY: HTML included in message -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature X-Headers-End: 1Wt2KA-0003pN-LB Subject: [Bitcoin-development] Possible attack: Keeping unconfirmed transactions X-BeenThere: bitcoin-development@lists.sourceforge.net X-Mailman-Version: 2.1.9 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 06 Jun 2014 22:09:23 -0000 --089e01227df4cccdcf04fb320948 Content-Type: text/plain; charset=UTF-8 I dont know if this attack is even possible, it came to my mind and I will try to explain it as good as possible. Some transacions keep unconfirmed forever and finally they are purged by Bitcoin nodes, mostly due to the lack of fees. Example: --------- Alice is selling a pizza to Bob, Bob is now making the payment with Bitcoin. The main goal of this attack is to store a unconfirmed transaction send by Bob for a few days (it will not be included in the blockchain because it has no fee or due to other reason), Bob might resend the payment or might just cancel the deal with Alice. Bob forgets about that failed trade but a couple of days later, Alice, who has stored the signed transacion, relays the transaction to the network (or mines it directly with his own hashpower). Bob does not know what is happening, he believed that that transaction was "canceled forever", he even does not remember the failed pizza deal. Alice has now the bitcoins and Bob does not know what happened with his money. --------- This might also work with the Payment Protocol because when using it Bob does not relay the transaction to the network, its Alices job to do it, Alice stores it and tells Bob to resend the payment, Bob creates another transaction (If has the same inputs as the first TX this does not work) (this one is relayed by Alice to the network). Alice comes back a couple of days later and mines with his hashrate the first transaction (the one she didnt relayed to the network). Alice now has two payments, Bob does not know what happened. ----------- I hope that I explained well this possible attack, I dont know if there is already a fix for this problem or if it is simply impossible to execute this kind of attack. Thanks for your time. --089e01227df4cccdcf04fb320948 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
I dont know if= this attack is even possible, it came to my mind and I will try to explain= it as good as possible.

Some transacions keep unconfirm= ed forever and finally they are purged by Bitcoin nodes, mostly due to the = lack of fees.


Example:
---------
<= br>
Alice is selling a pizza to Bob, Bob is now making the paymen= t with Bitcoin.
The main goal of this attack is to store a unconf= irmed transaction send by Bob for a few days (it will not be included in th= e blockchain because it has no fee or due to other reason), Bob might resen= d the payment or might just cancel the deal with Alice.

Bob forgets about that failed trade but a couple of day= s later, Alice, who has stored the signed transacion, relays the transactio= n to the network (or mines it directly with his own hashpower).
Bob does not know what is happening, he believed that that transaction was = "canceled forever", he even does not remember the failed pizza de= al.

Alice has now the bitcoins and Bob does not kn= ow what happened with his money.

---------

This might also work= with the Payment Protocol because when using it Bob does not relay the tra= nsaction to the network, its Alices job to do it, Alice stores it and tells= Bob to resend the payment, Bob creates another transaction (If has the sam= e inputs as the first TX this does not work) (this one is relayed by Alice = to the network).

Alice comes back a couple of days later and mines with = his hashrate the first transaction (the one she didnt relayed to the networ= k).

Alice now has two payments, Bob does not know = what happened.


-----------

I h= ope that I explained well this possible attack, I dont know if there is alr= eady a fix for this problem or if it is simply impossible to execute this k= ind of attack.

Thanks for your time.
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