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-rw-r--r-- | bip-0322.mediawiki | 115 |
1 files changed, 85 insertions, 30 deletions
diff --git a/bip-0322.mediawiki b/bip-0322.mediawiki index 5191143..6d0fb78 100644 --- a/bip-0322.mediawiki +++ b/bip-0322.mediawiki @@ -23,7 +23,7 @@ The current message signing standard only works for P2PKH (1...) addresses. By e A new structure <code>SignatureProof</code> is added, which is a simple serializable scriptSig & witness container. -Two actions "Sign" and "Verify" are defined along with two *purposes* "SignMessage" and "ProveFunds". +Two actions "Sign" and "Verify" are defined along with one ''purpose'', "SignMessage", with the ability to expand in the future to add a potential "ProveFunds" purpose. === SignatureProof container === @@ -36,11 +36,7 @@ Two actions "Sign" and "Verify" are defined along with two *purposes* "SignMessa |- |Uint32||4||flags||standard flags (1-to-1 with standard flags in Bitcoin Core) |- -|VarInt||1-8||msglen||Number of bytes in message string, excluding NUL termination -|- -|Char*||[msglen]||msg||The message being signed for all subjects, excluding NUL termination -|- -|Uint8||1||entries||Number of proof entries<ref><strong>Why support multiple proofs?</strong> In particular with proof of funds, it is non-trivial to check a large number of individual proofs (one per UTXO) for duplicates. Software could be written to do so, but it seems more efficient to build this check into the specification itself.</ref> +|Uint8||1||entries||number of proof entries<ref><strong>Why support multiple proofs?</strong> It is non-trivial to check a large number of individual proofs for duplicates. Software could be written to do so, but it seems more efficient to build this check into the specification itself.</ref> |} The above is followed by [entries] number of signature entries: @@ -56,9 +52,9 @@ The above is followed by [entries] number of signature entries: |- |Uint8*||[scriptsiglen]||scriptsig||ScriptSig data |- -|VarInt||1-8||witlen||Number of bytes in witness data +|VarInt||1-8||witlen||Number of entries in witness stack |- -|Uint8*||[witlen]||wit||Witness +|Uint8[]*||[witlen]||wit||Witness stack, as [witlen] uint8* vectors, each one prepended with a varint of its size |} In some cases, the scriptsig or wit may be empty. If both are empty, the proof is incomplete. @@ -80,36 +76,24 @@ A verification call will return a result code according to the table below. |- |INVALID||One or more of the given proofs were invalid |- -|SPENT||One or more of the claimed UTXO:s has been spent -|- |ERROR||An error was encountered |} == Signing and Verifying == -Let there be an empty set `inputs` which is populated and tested at each call to one of the actions below. +If the challenge consists of a single address and the address is in the P2PK(H) (legacy) format, sign using the legacy format (further information below). Otherwise continue as stated below. + +Let there be an empty set <code>inputs</code> which is populated and tested at each call to one of the actions below. === Purpose: SignMessage === The "SignMessage" purpose generates a sighash based on a scriptPubKey and a message. It emits a VALID verification result code unless otherwise stated. -# Return INVALID if scriptPubKey already exists in `inputs` set, otherwise insert it<ref><strong>Why track duplicates?</strong> Because a 3-entry proof is not proving 3 inputs unless they are all distinct</ref> +# Return INVALID if scriptPubKey already exists in <code>inputs</code> set, otherwise insert it<ref><strong>Why track duplicates?</strong> Because a 3-entry proof is not proving 3 entries unless they are all distinct</ref> # Define the message pre-image as the sequence "Bitcoin Message:" concatenated with the message, encoded in UTF-8 using Normalization Form Compatibility Decomposition (NFKD) # Let sighash = sha256(sha256(scriptPubKey || pre-image)) -=== Purpose: ProveFunds === - -The "ProveFunds" purpose generates a sighash and a scriptPubKey from a transaction, an output index, and a message. For multiple simultaneous proofs, it also requires access to the ordered list of proofs. It emits a VALID verification result code unless otherwise stated. - -# Let txid be the transaction ID of the transaction, and vout be the output index corresponding to the index of the output being spent -# Return INVALID if the txid:vout pair already exists in `inputs` set, otherwise insert it -# Return SPENT if the txid/vout is not a valid UTXO according to a Bitcoin node<ref><strong>Synced up or not?</strong> A normal verifier would use a synced up node. An auditor checking records from a client that were submitted in the past want to use a node that is synced up to the block corresponding to the proof, or the proof will fail, even if it may have been valid at the time of creation.</ref> -# Extract scriptPubKey from transaction output -# Define the message pre-image as the concatenation of the following components:<ref><strong>Why not just the UTXO data?</strong> We want the verifier to be able to challenge the prover with a custom message to sign, or anyone can reuse the POF proof for a set of UTXO:s once they have seen it, and the funds have not yet been spent</ref> -#* the string "POF:" -#* the message, encoded in UTF-8 using Normalization Form Compatibility Decomposition (NFKD), including the null terminating character (i.e. write strlen(message) + 1 bytes, for a C string) -#* all transactions being proven for, as binary txid (little endian uint256) followed by index (little endian uint32), each separated by a single `0x00` byte -# Let sighash = sha256(sha256(scriptPubKey || pre-image)) +A private key may be used directly to sign a message. In this case, its P2WPKH bech32 address shall be derived, and used as the input. === Action: Sign === @@ -119,6 +103,8 @@ The "Sign" action takes as input a purpose. It returns a signature or fails. # Derive the private key privkey for the scriptPubKey; FAIL if not VALID # Generate and return a signature sig with privkey=privkey, sighash=sighash +The resulting signature proof should be encoded using base64 encoding. + === Action: Verify === The "Verify" action takes as input a standard flags value, a script sig, an optional witness, and a purpose. @@ -139,13 +125,39 @@ Note that the order of the entries in the proof must match the order of the entr * If a verification call returns ERROR or INVALID, return ERROR or INVALID immediately, ignoring as yet unverified entries * After all verifications complete, ** return INCONCLUSIVE if any verification call returned INCONCLUSIVE -** return SPENT if any verification call returned SPENT ** return INCOMPLETE if the INCOMPLETE flag is set ** return VALID +== Legacy format == + +The legacy format is restricted to the legacy P2PK(H) address format, and restricted to one single challenge (address). + +Any other input (e.g. multiple addresses, or non-P2PK(H) address format(s)) must be signed using the new format described above. + +=== Signing === + +Given the P2PK(H) address <code>a</code> and the message <code>m</code>: +# let <code>p</code> be the pubkey-hash contained in <code>a</code> +# let <code>x</code> be the private key associated with <code>p</code> +# let <code>digest</code> be <code>SHA56d("Bitcoin Signed Message:\n"||m)</code> +# create a compact signature <code>sig</code> (aka "recoverable ECDSA signature") using <code>x</code> on <code>digest</code> + +The resulting proof is <code>sig</code>, serialized using the base64 encoding. + +=== Verifying === + +Given the P2PK(H) address <code>a</code>, the message <code>m</code>, and the compact signature <code>sig</code>: + +# let <code>p</code> be the pubkey-hash contained in <code>a</code> +# let <code>digest</code> be <code>SHA56d("Bitcoin Signed Message:\n"||m)</code> +# attempt pubkey recovery for <code>digest</code> using the signature <code>sig</code> and store the resulting pubkey into <code>Q</code> +## fail verification if pubkey recovery above fails +# let <code>q</code> be the pubkey-hash of <code>Q</code> +# if <code>p == q</code>, the proof is valid, otherwise it is invalid + == Compatibility == -This specification is not backwards compatible with the legacy signmessage/verifymessage specification. However, legacy addresses (1...) may be used in this implementation without any problems. +This specification is backwards compatible with the legacy signmessage/verifymessage specification through the special case as described above. == Rationale == @@ -153,17 +165,60 @@ This specification is not backwards compatible with the legacy signmessage/verif == Reference implementation == -To do. +# Pull request to Bitcoin Core: https://github.com/bitcoin/bitcoin/pull/16440 == Acknowledgements == -TODO +Thanks to David Harding, Jim Posen, Kalle Rosenbaum, Pieter Wuille, and many others for their feedback on the specification. == References == # Original mailing list thread: https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2018-March/015818.html -# Pull request, with comments: https://github.com/bitcoin/bips/pull/725 == Copyright == This document is licensed under the Creative Commons CC0 1.0 Universal license. + +== Test vectors == + +* <code>STANDARD_SCRIPT_VERIFY_FLAGS = 01ffdf (131039)</code> +* <code>address = 2MsnqGxX7Abtn4b379MEpkDaD3VbNKQosd8</code> +* <code>message = "hello world"</code> +* <code>sighash = 7b66a1861b4e179e1dbab4702e26bcefeabf1cada7cccc97b6ebaec89a035d84</code> (<code>sha256d("Bitcoin Message:hello world")</code>) + +A possible proof is: + +* HEX: <code>dfff01000117160014689bbb5d76774321c652832ea209958fa1770b330247304402204368b119399d33b9bc9beef06d713becefd3ac508dc95ff62d1859d4912960c7022063d88ddc648faed710b3f870b7a839fdc1b3bfc3c3bd065df51bbbd8c386c81c012102b4e4c6d5021576a5c0bc4535890c3f17e1ff23a94eac87beb0a5e8747c42d920</code> +* Base64: <code>3/8BAAEXFgAUaJu7XXZ3QyHGUoMuogmVj6F3CzMCRzBEAiBDaLEZOZ0zubyb7vBtcTvs79OsUI3JX/YtGFnUkSlgxwIgY9iN3GSPrtcQs/hwt6g5/cGzv8PDvQZd9Ru72MOGyBwBIQK05MbVAhV2pcC8RTWJDD8X4f8jqU6sh76wpeh0fELZIA==</code> + +Split into components: + +{|class="wikitable" style="text-align: center;" +|- +!Type +!Length +!Name +!Value +!Comment +|- +|Uint32||4||flags||<code>dfff0100</code>||standard flags used in signing +|- +|Uint8||1||entries||<code>01</code>||1 entry +|- +|VarInt||1-8||scriptsiglen||<code>17</code>||23 byte scriptsig +|- +|Uint8[32]||32||scriptsig||<code>160014689bbb5d76774321c652832ea209958fa1770b33</code>||ScriptSig data +|- +|VarInt||1-8||witlen||<code>02</code>||2 entries in witness stack +|- +|VarInt||1-8||entry1len||<code>47</code>||71 byte entry +|- +|Uint8[71]||71||entry1||<code>304402204368b119399d33b9bc9beef06d713becefd3ac50 +8dc95ff62d1859d4912960c7022063d88ddc648faed710b3 +f870b7a839fdc1b3bfc3c3bd065df51bbbd8c386c81c01</code>||Witness stack item 1 +|- +|VarInt||1-8||entry2len||<code>21</code>||33 byte entry +|- +|Uint8[33]||33||entry2||<code>02b4e4c6d5021576a5c0bc4535890c3f17e1ff23a94eac87 +beb0a5e8747c42d920</code>||Witness stack item 2 +|} |