Silent Payments: sending

josibake commented at 4:37 pm on August 2, 2023: member

This PR is part of integrating silent payments into Bitcoin Core. Status and tracking for the project is managed in #28536

This PR depends on #28122 and is marked as a draft until it is merged. If interested in those commits, please review on #28122

Pre-work / Refactors

The first three commits are pre-work / refactors needed for this PR. They are broken out into the following PRS:

Sending

Silent Payments logic

The main focus of this PR is:

Applying the Taptweak to a taproot internal private key (this is a copy-paste of the code for applying the taptweak in the signing process)
Getting a private key from a given scriptPubKey
Creating silent payment outputs
Applying the created scriptPubKeys back to the vector of CRecipients

The functions are then used together to create silent payment outputs during CreateTransactionInternal.

Final steps

The last commits ensure that:

Coin selection is silent payments aware and knows to exclude taproot script path spends and inputs with unknown witness when funding a transaction which pays to a silent payment address
The change output type is correctly chosen when paying to a silent payment address
Functional tests

DrahtBot commented at 4:37 pm on August 2, 2023: contributor

The following sections might be updated with supplementary metadata relevant to reviewers and maintainers.

Code Coverage & Benchmarks

For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/28201.

Reviews

See the guideline for information on the review process. A summary of reviews will appear here.

Conflicts

Reviewers, this pull request conflicts with the following ones:

#32523 (wallet: Remove watchonly behavior and isminetypes by achow101)
#32238 (qt, wallet: Convert uint256 to Txid by marcofleon)
#31974 (Drop testnet3 by Sjors)
#31936 (rpc: Support v3 raw transactions creation by Bue-von-hon)
#28333 (wallet: Construct ScriptPubKeyMans with all data rather than loaded progressively by achow101)
#27865 (wallet: Track no-longer-spendable TXOs separately by achow101)
#27286 (wallet: Keep track of the wallet’s own transaction outputs in memory by achow101)
#27260 (Enhanced error messages for invalid network prefix during address parsing. by portlandhodl)

If you consider this pull request important, please also help to review the conflicting pull requests. Ideally, start with the one that should be merged first.

LLM Linter (✨ experimental)

Possible typos and grammar issues:

faily -> fail [typographical error]
mutltiple -> multiple [typographical error]
ouput -> output [typographical error]
+at least one is manually selected. Can -> at least one is manually selected. Can [stray character from diff format]
reedeemScript, we have know way -> redeemScript, we have no way [typographical and grammatical error]

DrahtBot added the label CI failed on Aug 2, 2023

josibake renamed this:
~~Silent Payments: implement sending~~
Silent Payments: sending
on Aug 3, 2023

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josibake commented at 9:50 am on August 3, 2023: member

Maybe add a quick summary in the description with the main implementation differences relative to #24897. It seems a big one is that this doesn’t require an index!

updated! I added the summary in #27827 and added links back to the parent PR in each of the child PRs.

in src/wallet/spend.cpp:942 in 181e329a1d outdated

899+    assert(tx_outpoints.size() > 0);
900+    CKey scalar_ecdh_input = PrepareScalarECDHInput(input_private_keys, tx_outpoints);
901+    std::vector<SilentPaymentRecipient> silent_payment_recipients = GroupSilentPaymentAddresses(silent_payment_destinations);
902+    std::vector<CRecipient> outputs;
903+    for (const auto& recipient : silent_payment_recipients) {
904+        Sender sender{scalar_ecdh_input, recipient};

josibake commented at 10:29 am on August 8, 2023:

This does not need to be a struct, it can just be a function.

in test/functional/wallet_silentpayments_sending.py:110 in e6f7458324 outdated

86+            address=SILENT_PAYMENT_ADDRESS,
87+            amount=21,
88+        )
89+        assert txid
90+
91+    def test_deterministic_send(self):

BrandonOdiwuor commented at 5:32 pm on August 9, 2023:

Incorporating logs within the test is crucial for offering transparent insight into the test’s progression, simplifying the identification of problems, and enhancing comprehension of the test’s overall behavior.

in test/functional/wallet_silentpayments_sending.py:160 in e6f7458324 outdated

122+                assert output["scriptPubKey"]["address"] == "bcrt1p5num3dvry0ffusg3s7v2j5fy025p95jtn6js65jlruwc69r9je2s6qfsj7"
123+                break
124+        else:
125+            assert False
126+
127+    def test_address_reuse(self):

BrandonOdiwuor commented at 5:34 pm on August 9, 2023:

Also consider adding logs to this test as the ones above

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josibake commented at 4:30 pm on September 26, 2023: member

Note: send does not work, but sendall, sendtoaddress does

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DrahtBot commented at 9:36 pm on January 17, 2024: contributor

🚧 At least one of the CI tasks failed. Make sure to run all tests locally, according to the documentation.

Possibly this is due to a silent merge conflict (the changes in this pull request being incompatible with the current code in the target branch). If so, make sure to rebase on the latest commit of the target branch.

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Debug: https://github.com/bitcoin/bitcoin/runs/20505330863

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josibake commented at 2:30 pm on January 19, 2024: member

Rebased https://github.com/bitcoin/bitcoin/commit/3f4b0f77c7f2ff52b9c84bf1c5a70281a066cfe2 -> https://github.com/bitcoin/bitcoin/commit/3b0dd79cacaf4e97489746ace5c1c8d6fe8db38d (implement-bip352-sending-01 -> implement-bip352-01-rebase, compare)

Fixed silent merge conflict with CKey now returning std::byte*

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Debug: https://github.com/bitcoin/bitcoin/runs/24114299414

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🚧 At least one of the CI tasks failed. Debug: https://github.com/bitcoin/bitcoin/runs/27794809832

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Squashed 'src/secp256k1/' changes from 4187a46649..c0db6509bd

c0db6509bd docs: update README
8339232b7e ci: enable silentpayments module
635745fc3a tests: add constant time tests
b1de2ee2f7 tests: add BIP-352 test vectors
aea372837f silentpayments: add benchmarks for scanning
1ec7857aed silentpayments: add examples/silentpayments.c
c9bec084eb silentpayments: receiving
28fd17d7c4 silentpayments: recipient label support
065e8b7793 silentpayments: sending
a6d8b11754 build: add skeleton for new silentpayments (BIP352) module
6274359346 bench: add ellswift to bench help output
0258186573 configure: Show exhaustive tests in summary
53b578d10b include: remove WARN_UNUSED_RESULT for functions always returning 1
f75c985604 ci: Fix exiting from ci.sh on error
947761b842 tests: remove unused uncounting_illegal_callback_fn
5d01f375c6 build: Drop no longer needed  `-fvisibility=hidden` compiler option
dbf1e95d2a ci: Run `tools/symbol-check.py`
8174c88f47 test: Add `tools/symbol-check.py`
8a287f9a32 Introduce `SECP256K1_LOCAL_VAR` macro
7106544a16 Remove deprecated _ec_privkey_{negate,tweak_add,tweak_mul} aliases
1e2da62eff gha: Print all *.log files, in a separate action
REVERT: 4187a46649 Merge bitcoin-core/secp256k1#1492: tests: Add Wycheproof ECDH vectors
REVERT: e266ba11ae tests: Add Wycheproof ECDH vectors
REVERT: 13906b7154 Merge bitcoin-core/secp256k1#1669: gitignore: Add Python cache files
REVERT: c1bcb03276 gitignore: Add Python cache files
REVERT: 70f149b9a1 Merge bitcoin-core/secp256k1#1662: bench: add ellswift to bench help output
REVERT: 6b3fe51fb6 bench: add ellswift to bench help output
REVERT: d84bb83e26 Merge bitcoin-core/secp256k1#1661: configure: Show exhaustive tests in summary
REVERT: 3f54ed8c1b Merge bitcoin-core/secp256k1#1659: include: remove WARN_UNUSED_RESULT for functions always returning 1
REVERT: 20b05c9d3f configure: Show exhaustive tests in summary
REVERT: e56716a3bc Merge bitcoin-core/secp256k1#1660: ci: Fix exiting from ci.sh on error
REVERT: d87c3bc58f ci: Fix exiting from ci.sh on error
REVERT: 1b6e081538 include: remove WARN_UNUSED_RESULT for functions always returning 1
REVERT: 2abb35b034 Merge bitcoin-core/secp256k1#1657: tests: remove unused uncounting_illegal_callback_fn
REVERT: 51907fa918 tests: remove unused uncounting_illegal_callback_fn
REVERT: a7a5117144 Merge bitcoin-core/secp256k1#1359: Fix symbol visibility issues, add test for it
REVERT: 13ed6f65dc Merge bitcoin-core/secp256k1#1593: Remove deprecated `_ec_privkey_{negate,tweak_add,tweak_mul}` aliases from API
REVERT: d1478763a5 build: Drop no longer needed  `-fvisibility=hidden` compiler option
REVERT: 8ed1d83d92 ci: Run `tools/symbol-check.py`
REVERT: 41d32ab2de test: Add `tools/symbol-check.py`
REVERT: 88548058b3 Introduce `SECP256K1_LOCAL_VAR` macro
REVERT: 03bbe8c615 Merge bitcoin-core/secp256k1#1655: gha: Print all *.log files, in a separate action
REVERT: 59860bcc24 gha: Print all *.log files, in a separate action
REVERT: 37d2c60bec Remove deprecated _ec_privkey_{negate,tweak_add,tweak_mul} aliases

git-subtree-dir: src/secp256k1
git-subtree-split: c0db6509bd2cb0777ce0d335e2582f74364fb8ec

497f1536ef

Merge commit '497f1536ef9774ce0dd7d2225a5d79cc3811c0f8' into refresh-secp256k1 7cf15ce8fd

crypto: add read-only method to KeyPair

Add a method for passing a KeyPair object to secp256k1 functions expecting a secp256k1_keypair.
This allows for passing a KeyPair directly to a secp256k1 function without needing to create a
temporary secp256k1_keypair object.

f19fd5581b

Add "sp" HRP 8c820eeb5b

Add V0SilentPaymentDestination address type cd2ec52462

common: add bip352.{h,cpp} secp256k1 module

Wrap the silentpayments module from libsecp256k1. This is placed in
common as it is intended to be used by:

  * RPCs: for parsing addresses
  * Wallet: for sending, receiving, spending silent payment outputs
  * Node: for creating silent payment indexes for light clients

84cc673356

wallet: disable sending to silent payment address

Have `IsValidDestination` return false for silent payment destinations
and set an error string when decoding a silent payment address.

This prevents anyone from sending to a silent payment address before
sending is implemented in the wallet, but also allows the functions to
be used in the unit testing famework.

d766390f8d

tests: add BIP352 test vectors as unit tests

Use the test vectors to test sending and receiving. A few cases are not
covered here, namely anything that requires testing specific to the
wallet. For example:

* Taproot script path spending is not tested, as that is better tested in
  a wallets coin selection / signing logic
* Re-computing outputs during RBF is not tested, as that is better
  tested in a wallets RBF logic

The unit tests are written in such a way that adding new test cases is
as easy as updating the JSON file

51b6e003d2

wallet: get serialized size for `V0SilentPayments`

BIP352 v0 specifies that a silent payment output is a taproot output.
Taproot scriptPubKeys are a fixed size, so when calculating the
serialized size for a CRecipient with a V0SilentPayments destination,
use WitnessV1Taproot for the serialized txout size.

ab274e40d0

wallet: add method for retreiving a private key

Add a method for retreiving a private key for a given scriptPubKey.
If the scriptPubKey is a taproot output, tweak the private key with the
merkle root or hash of the public key, if applicable.

976a536e8d

wallet: make coin selection silent payment aware

Add a flag to the `CoinControl` object if silent payment destinations
are provided. Before adding the flag, call a function which checks if:

* The wallet has private keys
* The wallet is unlocked

Without both of the above being true, we cannot send to a silent payment
address.

During coin selection, if this flag is set, skip taproot inputs when
script spend data is available. This is based on the assumption that if
a user provides script spend data, they don't have access to the key
path spend. As future improvement, we could instead check to see if we
have access to the key path spend, and only exclude the output when we
don't regardless of whether or not the user provides script spend data.

Also skip UTXOs of type `WITNESS_UNKNOWN`, although it is very unlikely
our wallet would ever try to spend a witness unknown output.

7dfe383e9b

wallet: add `IsInputForSharedSecretDerivation` function 793a4182df

wallet: add `CreateSilentPaymentOutputs` function

`CreateSilentPaymentsOutputs` gets the correct private keys, adds them
together, groups the silent payment destinations and then generates the
taproot script pubkeys. These are then passed back to
CreateTransactionInternal, which uses these scriptPubKeys to update
vecSend before adding them to the transaction outputs.

66f5ece385

wallet: update TransactionChangeType

If sending to a silent payment destination, the change type should be taproot

f59c88d580

wallet: enable sending to silent payment address 180b982848

tests: add sending functional tests fce7788d0d

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DrahtBot commented at 9:39 am on May 16, 2025: contributor

🐙 This pull request conflicts with the target branch and needs rebase.

DrahtBot added the label Needs rebase on May 16, 2025

Silent Payments: sending #28201

Pre-work / Refactors

Sending

Silent Payments logic

Final steps

Code Coverage & Benchmarks

Reviews

Conflicts

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