Add experimental silent payment transaction creation support

Cargo.toml

@@ -31,6 +31,7 @@ bdk_redb = { version = "0.1.0", optional = true }
 shlex = {  version = "1.3.0", optional = true }
 tracing = "0.1.41"
 tracing-subscriber = "0.3.20"
+bdk_sp = { version = "0.1.0", optional = true, git = "https://github.com/bitcoindevkit/bdk-sp", tag = "v0.1.0" }
 
 [features]
 default = ["repl", "sqlite"]
@@ -54,3 +55,6 @@ verify = []
 # Extra utility tools
 # Compile policies
 compiler = []
+
+# Experimental silent payment sending capabilities
+sp = ["dep:bdk_sp"]

README.md

@@ -112,6 +112,27 @@ To generate a new extended master key, suitable for use in a descriptor:
 cargo run -- key generate
 ```
 
+#### Silent payments
+
+> [!WARNING]
+> This tool does not support silent payment scanning, nor the `silent_payment_code`
+> command has any control on the public keys provided. If you don't have access
+> to a silent payment scanner with the keys you provided, you are not going to
+> be able to discover any funds, and if you do not control the private keys,
+> you are not going to be able to spend the funds. We do not recommend the use
+> of any of the silent payment features with real funds.
+
+To experiment with silent payments, you can get two public keys in compressed format, `A1` and `A2`, and produce a silent payment code by calling:
+```shell
+cargo run --features sp -- --network signet silent_payment_code --scan_public_key '<A1>' --spend_public_key '<A2>'
+```
+
+Once you have a silent payment code, `SP_CODE_1` and an amount `AMOUNT_1` to send, you can create a valid transaction locking funds to a silent payment code derived address with the following command:
+
+```shell
+cargo run --features electrum,sp -- --network testnet4 wallet --wallet sample_wallet --ext-descriptor "wpkh(tpubEBr4i6yk5nf5DAaJpsi9N2pPYBeJ7fZ5Z9rmN4977iYLCGco1VyjB9tvvuvYtfZzjD5A8igzgw3HeWeeKFmanHYqksqZXYXGsw5zjnj7KM9/*)" --database-type sqlite --client-type electrum --url "ssl://mempool.space:40002" create_sp_tx --to-sp <SP_CODE_1>:<AMOUNT_1>
+```
+
 ## Justfile
 
 We have added the `just` command runner to help you with common commands (during development) and running regtest `bitcoind` if you are using the `rpc` feature. 

src/commands.rs

@@ -14,6 +14,9 @@
 
 #![allow(clippy::large_enum_variant)]
 
+#[cfg(feature = "sp")]
+use {crate::utils::parse_sp_code_value_pairs, bdk_sp::encoding::SilentPaymentCode};
+
 use bdk_wallet::bitcoin::{
     Address, Network, OutPoint, ScriptBuf,
     bip32::{DerivationPath, Xpriv},
@@ -107,6 +110,19 @@ pub enum CliSubCommand {
         #[command(flatten)]
         wallet_opts: WalletOpts,
     },
+    /// Silent payment code generation tool.
+    ///
+    /// Allows the encoding of two public keys into a silent payment code.
+    /// Useful to create silent payment transactions using fake silent payment codes.
+    #[cfg(feature = "sp")]
+    SilentPaymentCode {
+        /// The scan public key to use on the silent payment code.
+        #[arg(long = "scan_public_key")]
+        scan: bdk_sp::bitcoin::secp256k1::PublicKey,
+        /// The spend public key to use on the silent payment code.
+        #[arg(long = "spend_public_key")]
+        spend: bdk_sp::bitcoin::secp256k1::PublicKey,
+    }
 }
 
 /// Wallet operation subcommands.
@@ -311,6 +327,62 @@ pub enum OfflineWalletSubCommand {
         )]
         add_data: Option<String>, //base 64 econding
     },
+    /// Creates a silent payment transaction
+    ///
+    /// This sub-command is **EXPERIMENTAL** and should only be used for testing. Do not use this
+    /// feature to create transactions that spend actual funds on the Bitcoin mainnet.
+
+    // This command DOES NOT return a PSBT. Instead, it directly returns a signed transaction
+    // ready for broadcast, as it is not yet possible to perform a shared derivation of a silent
+    // payment script pubkey in a secure and trustless manner.
+    #[cfg(feature = "sp")]
+    CreateSpTx {
+        /// Adds a recipient to the transaction.
+        // Clap Doesn't support complex vector parsing https://github.com/clap-rs/clap/issues/1704.
+        // Address and amount parsing is done at run time in handler function.
+        #[arg(env = "ADDRESS:SAT", long = "to", required = false, value_parser = parse_recipient)]
+        recipients: Option<Vec<(ScriptBuf, u64)>>,
+        /// Parse silent payment recipients
+        #[arg(long = "to-sp", required = true, value_parser = parse_sp_code_value_pairs)]
+        silent_payment_recipients: Vec<(SilentPaymentCode, u64)>,
+        /// Sends all the funds (or all the selected utxos). Requires only one recipient with value 0.
+        #[arg(long = "send_all", short = 'a')]
+        send_all: bool,
+        /// Make a PSBT that can be signed by offline signers and hardware wallets. Forces the addition of `non_witness_utxo` and more details to let the signer identify the change output.
+        #[arg(long = "offline_signer")]
+        offline_signer: bool,
+        /// Selects which utxos *must* be spent.
+        #[arg(env = "MUST_SPEND_TXID:VOUT", long = "utxos", value_parser = parse_outpoint)]
+        utxos: Option<Vec<OutPoint>>,
+        /// Marks a utxo as unspendable.
+        #[arg(env = "CANT_SPEND_TXID:VOUT", long = "unspendable", value_parser = parse_outpoint)]
+        unspendable: Option<Vec<OutPoint>>,
+        /// Fee rate to use in sat/vbyte.
+        #[arg(env = "SATS_VBYTE", short = 'f', long = "fee_rate")]
+        fee_rate: Option<f32>,
+        /// Selects which policy should be used to satisfy the external descriptor.
+        #[arg(env = "EXT_POLICY", long = "external_policy")]
+        external_policy: Option<String>,
+        /// Selects which policy should be used to satisfy the internal descriptor.
+        #[arg(env = "INT_POLICY", long = "internal_policy")]
+        internal_policy: Option<String>,
+        /// Optionally create an OP_RETURN output containing given String in utf8 encoding (max 80 bytes)
+        #[arg(
+            env = "ADD_STRING",
+            long = "add_string",
+            short = 's',
+            conflicts_with = "add_data"
+        )]
+        add_string: Option<String>,
+        /// Optionally create an OP_RETURN output containing given base64 encoded String. (max 80 bytes)
+        #[arg(
+            env = "ADD_DATA",
+            long = "add_data",
+            short = 'o',
+            conflicts_with = "add_string"
+        )]
+        add_data: Option<String>, //base 64 econding
+    },
     /// Bumps the fees of an RBF transaction.
     BumpFee {
         /// TXID of the transaction to update.

src/error.rs

@@ -21,6 +21,9 @@ pub enum BDKCliError {
     #[error("Create transaction error: {0}")]
     CreateTx(#[from] bdk_wallet::error::CreateTxError),
 
+    #[error("Silent payment address decoding error: {0}")]
+    SilentPaymentParseError(#[from] bdk_sp::encoding::ParseError),
+
     #[error("Descriptor error: {0}")]
     DescriptorError(#[from] bdk_wallet::descriptor::error::Error),