From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from sog-mx-3.v43.ch3.sourceforge.com ([172.29.43.193] helo=mx.sourceforge.net) by sfs-ml-4.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1UomuP-0007LW-EO for bitcoin-development@lists.sourceforge.net; Tue, 18 Jun 2013 03:48:41 +0000 Received-SPF: pass (sog-mx-3.v43.ch3.sourceforge.com: domain of gmail.com designates 209.85.223.170 as permitted sender) client-ip=209.85.223.170; envelope-from=etotheipi@gmail.com; helo=mail-ie0-f170.google.com; Received: from mail-ie0-f170.google.com ([209.85.223.170]) by sog-mx-3.v43.ch3.sourceforge.com with esmtps (TLSv1:RC4-SHA:128) (Exim 4.76) id 1UomuK-0007xU-U6 for bitcoin-development@lists.sourceforge.net; Tue, 18 Jun 2013 03:48:41 +0000 Received: by mail-ie0-f170.google.com with SMTP id e11so8922077iej.15 for ; Mon, 17 Jun 2013 20:48:31 -0700 (PDT) X-Received: by 10.50.57.48 with SMTP id f16mr6438357igq.72.1371527311637; Mon, 17 Jun 2013 20:48:31 -0700 (PDT) Received: from [192.168.1.85] (c-76-111-96-126.hsd1.md.comcast.net. [76.111.96.126]) by mx.google.com with ESMTPSA id ie16sm20453162igb.4.2013.06.17.20.48.28 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Mon, 17 Jun 2013 20:48:29 -0700 (PDT) Message-ID: <51BFD886.8000701@gmail.com> Date: Mon, 17 Jun 2013 23:48:22 -0400 From: Alan Reiner User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130510 Thunderbird/17.0.6 MIME-Version: 1.0 To: Bitcoin Dev X-Enigmail-Version: 1.5.1 Content-Type: multipart/alternative; boundary="------------060600080401050209080308" 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 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (etotheipi[at]gmail.com) -0.0 SPF_PASS SPF: sender matches SPF record 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: 1UomuK-0007xU-U6 Subject: [Bitcoin-development] Optional "wallet-linkable" address format - Payment Protocol 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: Tue, 18 Jun 2013 03:48:41 -0000 This is a multi-part message in MIME format. --------------060600080401050209080308 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit _*Goal*_: An alternative address format made possible by BIP 32, which allows one to specify a "Wallet ID" and "One-time payment" code, instead of the standard one-use Base58-Hash160 addresses. This allows parties with a persistent relationship to be able to prove that payment addresses they provide each other are linked to a particular wallet, reducing exposure to MitM attacks without the need for SSL or a web of trust, and without compromising the privacy of either party. For instance, this could be used between businesses that frequently do business, by exchanging and verifying public keys beforehand, or could be used by an exchange to identify if a customer withdrawal address is related to their last deposit address, and if not enforce extra authentication measures. _*Background*__:_ I haven't been following the payment protocol discussions/development much, so I apologize if this has already been addressed. I'm calling it "wallet-linkable" addresses, which would be an optional second form for sending someone your address. With BIP 32, the address is computed by the payee (the person sending the address to receive money): Standard Address ~ Base58(0x00 || hash160(PubKeyParent * Multiplier[i]) || checksum) What I'd like to do is have the option, when specifying an address through the payment protocol, to send *just* the {PublicKeyParent, Multiplier[i]} and let the receiver of that address compute the address on their own. This is no significant burden on the receiver, but it does provide the useful property that they can recognize when addresses specified in this way come from the same wallet -- because the PubKeyParent will be the same. Remember, this is _optional_ for the person providing the address. One nice, accidental feature of BIP 32 is that the Multiplier[i] used above does not actually reveal the "chaincode" (I think Pieter started calling it the "tweak"). It is derived from the chaincode but doesn't reveal it. Therefore, the payer sees the parent public key, but that's not useful to derive any of the other addresses unless they also have the chaincode. But they can verify that the PublicKeyParent is identical between transactions, and thus is accessible only to that wallet. It allows them validate a specific address provided by the payee, but not generate or identify any other addresses. *_Use Cases:_* (1) So, just like with PGP/GPG, when two parties decide they will start a relationship, they can start by exchanging the public keys of their wallet and verify them in a reliable manner. After that, when one party requests a payment address from the other, they can optionally send {PubKey, Multiplier}, and the payer's software will identify the owner of that address, or let you select who you think the address belongs to and it will verify it. If the payee's system is compromised and address is replaced, the address received by the payer won't validate. This doesn't help if the side sending the money is compromised. (2) When a customer first provides a deposit to an exchange, it will send money from an address in their wallet and the software will provide the exchange the {PubKey,Mult}. When the customer later provides a withdrawal address, the site can automatically trust the address as long it is provided in the alternate form and the public keys match. If they don't, it might be the same customer just requesting a withdrawal to a different wallet, which is fine, but they'll have to go through an extra verification step to do so. _*Downsides:*_ Multi-sig/P2SH - The only way this works with P2SH, violates one of the goals of P2SH slightly, but may not matter much if it's all done under the hood by the software. Instead of providing a 20-byte hash of a script, you provide all the public keys and multipliers for the individual addresses. The payer's software automatically verifies all addresses and creates the P2SH script itself (after a divine decree that public keys will always be sorted lexicographically in the multi-sig script). The blockchain still benefits from the "compression" of moving the bulky scripts to the TxIn, but it does require revealing more information than is necessary for the payer to pay the payee. But it may not /really/ be a problem, given the benefits. It might just be slightly longer strings to exchange during initialization and for each transaction. I have various reasons I'd like to use this, and it'd be nice to have some community backing, so I don't have to twist anyone's arm to trust me that it's legit. -Alan --------------060600080401050209080308 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Goal:  An alternative address format made possible by BIP 32, which allows one to specify a "Wallet ID" and "One-time payment" code, instead of the standard one-use Base58-Hash160 addresses.   This allows parties with a persistent relationship to be able to prove that payment addresses they provide each other are linked to a particular wallet, reducing exposure to MitM attacks without the need for SSL or a web of trust, and without compromising the privacy of either party.    For instance, this could be used between businesses that frequently do business, by exchanging and verifying public keys beforehand, or could be used by an exchange to identify if a customer withdrawal address is related to their last deposit address, and if not enforce extra authentication measures.

Background:
I haven't been following the payment protocol discussions/development much, so I apologize if this has already been addressed.   I'm calling it "wallet-linkable" addresses, which would be an optional second form for sending someone your address.   With BIP 32, the address is computed by the payee (the person sending the address to receive money):

   Standard Address ~ Base58(0x00 || hash160(PubKeyParent * Multiplier[i]) || checksum)

What I'd like to do is have the option, when specifying an address through the payment protocol, to send *just* the {PublicKeyParent, Multiplier[i]} and let the receiver of that address compute the address on their own.  This is no significant burden on the receiver, but it does provide the useful property that they can recognize when addresses specified in this way come from the same wallet -- because the PubKeyParent will be the same.  Remember, this is optional for the person providing the address.

One nice, accidental feature of BIP 32 is that the Multiplier[i] used above does not actually reveal the "chaincode" (I think Pieter started calling it the "tweak").   It is derived from the chaincode but doesn't reveal it.  Therefore, the payer sees the parent public key, but that's not useful to derive any of the other addresses unless they also have the chaincode.  But they can verify that the PublicKeyParent is identical between transactions, and thus is accessible only to that wallet.  It allows them validate a specific address provided by the payee, but not generate or identify any other addresses.

Use Cases:
(1)  So, just like with PGP/GPG, when two parties decide they will start a relationship, they can start by exchanging the public keys of their wallet and verify them in a reliable manner.  After that, when one party requests a payment address from the other, they can optionally send {PubKey, Multiplier}, and the payer's software will identify the owner of that address, or let you select who you think the address belongs to and it will verify it.  If the payee's system is compromised and address is replaced, the address received by the payer won't validate.  This doesn't help if the side sending the money is compromised.

(2)  When a customer first provides a deposit to an exchange, it will send money from an address in their wallet and the software will provide the exchange the {PubKey,Mult}.  When the customer later provides a withdrawal address, the site can automatically trust the address as long it is provided in the alternate form and the public keys match.  If they don't, it might be the same customer just requesting a withdrawal to a different wallet, which is fine, but they'll have to go through an extra verification step to do so. 


Downsides: 
Multi-sig/P2SH  - The only way this works with P2SH, violates one of the goals of P2SH slightly, but may not matter much if it's all done under the hood by the software.  Instead of providing a 20-byte hash of a script, you provide all the public keys and multipliers for the individual addresses.  The payer's software automatically verifies all addresses and creates the P2SH script itself (after a divine decree that public keys will always be sorted lexicographically in the multi-sig script).  The blockchain still benefits from the "compression" of moving the bulky scripts to the TxIn, but it does require revealing more information than is necessary for the payer to pay the payee.  But it may not really be a problem, given the benefits.  It might just be slightly longer strings to exchange during initialization and for each transaction.

I have various reasons I'd like to use this, and it'd be nice to have some community backing, so I don't have to twist anyone's arm to trust me that it's legit.

-Alan




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