From 8b11b6198144e499590d0f70b4f5681b5ded03ee Mon Sep 17 00:00:00 2001 From: Justus Ranvier Date: Tue, 19 Apr 2016 13:01:55 -0500 Subject: explain the usage of versions with regards to payment code behavior --- bip-0047.mediawiki | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) diff --git a/bip-0047.mediawiki b/bip-0047.mediawiki index 0720eb4..248fabc 100644 --- a/bip-0047.mediawiki +++ b/bip-0047.mediawiki @@ -84,7 +84,19 @@ Hardened derivation is used at this level. Except where noted, all keys derived from a payment code use the public derivation method. -==Standard Payment Codes (v1)== +==Versions== + +Payment codes contain a version byte which identifies a specific set of behavior. + +Unless otherwise specified, payment codes of different versions are interoperable. If Alice uses a version x payment code, and Bob uses a version y payment code, they can still send and receive transactions between each other. + +Currently specified versions: + +* Version 1 +** Address type: P2PKH +** Notification type: address + +==Version 1== ===Representation=== @@ -127,6 +139,8 @@ It is assumed that Alice can easily obtain Bob's payment code via a suitable met Prior to the first time Alice initiates a transaction to Bob, Alice MUST inform Bob of her payment code via the following procedure: +Note: this procedure is used if Bob uses a version 1 payment code (regardless of the the version of Alice's payment code). If Bob's payment code is not version 1, see the appropriate section in this specification. + # Alice constructs a transaction which sends a small quantity of bitcoins to Bob's notification address (notification transaction) ## The inputs selected for this transaction MUST NOT be easily associated with Alice's notification address # Alice derives a unique shared secret using ECDH: -- cgit v1.2.3 From 37a35b5565d5e56d46163872d992a8c0e80538bb Mon Sep 17 00:00:00 2001 From: Justus Ranvier Date: Tue, 19 Apr 2016 13:03:13 -0500 Subject: add recommended handling for notification tx change outputs --- bip-0047.mediawiki | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/bip-0047.mediawiki b/bip-0047.mediawiki index 248fabc..3f4f6eb 100644 --- a/bip-0047.mediawiki +++ b/bip-0047.mediawiki @@ -194,6 +194,17 @@ Alice SHOULD use an input script in one of the following standard forms to expos Compatible wallets MAY provide a method for a user to manually specify the public key associated with a notification transaction in order to recover payment codes sent via non-standard notification transactions. +=====Post-Notification Privacy Considerations===== + +Incautious handling of change outputs from notification transactions may cause unintended loss of privacy. + +The recipient of a transaction which spends a change output from a prior notification transaction will learn about the potential connection between the sender and the recipient of the notification transaction. + +The following actions are recommended to reduce this risk: + +* Wallets which support mixing SHOULD mix change outputs from notification transactions prior to spending them +* Wallets which do not support mixing MAY simulate mixing by creating a transaction which spends the change output to the next external BIP44 address + ====Sending==== # Each time Alice wants to initiate a transaction to Bob, Alice derives a unique P2PKH address for the transaction using ECDH follows: -- cgit v1.2.3 From 283aa14f77b633be67c647d294a35999723ce366 Mon Sep 17 00:00:00 2001 From: Justus Ranvier Date: Tue, 19 Apr 2016 13:04:59 -0500 Subject: add version 2 section for bloom filter-based notifications --- bip-0047.mediawiki | 45 ++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 44 insertions(+), 1 deletion(-) diff --git a/bip-0047.mediawiki b/bip-0047.mediawiki index 3f4f6eb..b1145b3 100644 --- a/bip-0047.mediawiki +++ b/bip-0047.mediawiki @@ -1,7 +1,7 @@ RECENT CHANGES: +* (19 Apr 2016) Define version 2 payment codes * (17 Apr 2016) Clarify usage of outpoints in notification transactions * (18 Dec 2015) Update explanations to resolve FAQs -* (12 Oct 2015) Revise blinding method for notification transactions 
   BIP: 47
@@ -95,6 +95,14 @@ Currently specified versions:
 * Version 1
 ** Address type: P2PKH
 ** Notification type: address
+* Version 2
+** Address type: P2PKH
+** Notification type: bloom-multisig
+
+===Recommended Versions===
+
+* Wallets which have bloom filtering capabilities SHOULD create version 2 payment codes instead of version 1 payment codes.
+* Version 1 payment codes are only recommended for wallets which lack access to bloom filtering capability.
 
 ==Version 1==
 
@@ -319,6 +327,41 @@ The sender transmits their payment code in base58 form to the calculated Bitmess
 
 In order to use Bitmessage notification, the recipient must have a Bitmessage client which listens at the address which the senders will derive and is capable of relaying received payment codes to the Bitcoin wallet.
 
+==Version 2==
+
+Version 2 payment codes behave identifically to version 1 payment codes, except as modified below.
+
+===Representation===
+
+====Binary Serialization====
+
+* Byte 0: version. required value: 0x02
+
+===Protocol===
+
+====Definitions====
+
+* Notification change output: the change output from a notification transaction which which resides in the sender's wallet, but can be automatically located by the intended recipient
+* Payment code identifier: a 33 byte representation of a payment code constructed by prepending 0x02 to the SHA256 hash of the binary serialization of the payment code
+
+====Notification Transaction====
+
+Note: this procedure is used if Bob uses a version 2 payment code (regardless of the the version of Alice's payment code). If Bob's payment code is not version 2, see the appropriate section in this specification.
+
+# Construct a notification transaction as per the version 1 instructions, except do not create the output to Bob's notification address
+# Create a notification change address as follows:
+## Obtain the pubkey corresponding to the next change address
+## Construct a multisig output in the form:
+
OP_1   OP_2 OP_CHECKMULTISIG

+
+The relative ordering of the payment code identifier and change address pubkey in the above script MAY be randomized
+
+Bob detects notification transactions by adding his payment code identifier to his bloom filter.
+
+# When the filter returns a notification transaction, the sender's payment code is unblinded using the same procedure as for version 1 notification transactions.
+
+Alice's wallet should spend the notification change output at the next appropriate opportunity.
+
 ==Test Vectors==
 
 * [[https://gist.github.com/SamouraiDev/6aad669604c5930864bd|BIP47 Reusable Payment Codes Test Vectors]]
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