Add example file

Cargo.toml

@@ -40,6 +40,10 @@ serde = { version = "1.0.103", default-features = false, optional = true }
 hashes = { package = "bitcoin_hashes", version = ">= 0.12, <= 0.14", default-features = false, optional = true }
 rand = { version = "0.8", default-features = false, optional = true }
 
+# only used in the example of silent payments
+libc = { version = "0.2", optional = true }
+cc = { version = "1.0", optional = true }
+
 [dev-dependencies]
 rand_core = "0.6"
 serde_cbor = "0.10.0"
@@ -66,6 +70,10 @@ required-features = ["hashes", "std"]
 name = "generate_keys"
 required-features = ["rand", "std"]
 
+[[example]]
+name = "silentpayments"
+required-features = ["rand", "std", "libc", "cc"]
+
 [workspace]
 members = ["secp256k1-sys"]
 exclude = ["no_std_test"]

examples/silentpayments.rs

@@ -0,0 +1,300 @@
+extern crate secp256k1;
+
+use secp256k1::{Keypair, PublicKey, Secp256k1, SecretKey, XOnlyPublicKey};
+use secp256k1::silentpayments::{
+    silentpayments_recipient_create_label_tweak, 
+    silentpayments_sender_create_outputs, 
+    SilentpaymentsRecipient, 
+    silentpayments_recipient_scan_outputs,
+    SilentpaymentsPublicData,
+    silentpayments_recipient_create_output_pubkey,
+    silentpayments_recipient_create_labelled_spend_pubkey
+};
+
+use libc::{c_uchar, c_void, size_t};
+use std::slice;
+
+#[repr(C)]
+#[derive(Debug, Copy, Clone)]
+struct LabelCacheEntry {
+    label: [u8; 33],
+    label_tweak: [u8; 32],
+}
+
+#[repr(C)]
+#[derive(Debug, Copy, Clone)]
+struct LabelsCache {
+    entries_used: size_t,
+    entries: [LabelCacheEntry; 5],
+}
+
+#[no_mangle]
+pub extern "C" fn rust_secp256k1_silentpayments_label_lookup(
+    label33: *const c_uchar,
+    cache_ptr: *const c_void,
+) -> *const c_uchar {
+    // Safety checks
+    if label33.is_null() || cache_ptr.is_null() {
+        return std::ptr::null();
+    }
+
+    unsafe {
+        let cache = &*(cache_ptr as *const LabelsCache);
+        let label33_slice = slice::from_raw_parts(label33, 33);
+
+        for i in 0..cache.entries_used {
+            if cache.entries[i].label == *label33_slice {
+                return cache.entries[i].label_tweak.as_ptr();
+            }
+        }
+
+        std::ptr::null()
+    }
+}
+
+fn main() {
+
+    let secp = Secp256k1::new();
+
+    let sender_secret_keys: [[u8; 32]; 2] = [
+        [
+            0x34, 0x18, 0x5f, 0xd2, 0xc0, 0xc3, 0x71, 0x19,
+            0x73, 0x46, 0x2e, 0xc7, 0x7b, 0x65, 0x69, 0x95,
+            0x43, 0x20, 0x5a, 0xee, 0x4f, 0x30, 0xf4, 0xee,
+            0x32, 0x5b, 0xd8, 0x37, 0x6a, 0x1b, 0x36, 0xf3
+        ],
+        [
+            0xcf, 0x3e, 0x69, 0x66, 0x58, 0xa9, 0x6e, 0x45,
+            0x70, 0x96, 0xcb, 0x2e, 0xc9, 0xa9, 0x7c, 0x27,
+            0x8c, 0x1b, 0xf0, 0xc6, 0x0d, 0x1d, 0xc3, 0x13,
+            0x92, 0x7d, 0xef, 0xac, 0xc2, 0x86, 0xae, 0x88
+        ]
+    ];
+
+    let smallest_outpoint: [u8; 36] = [
+        0x16, 0x9e, 0x1e, 0x83, 0xe9, 0x30, 0x85, 0x33, 0x91,
+        0xbc, 0x6f, 0x35, 0xf6, 0x05, 0xc6, 0x75, 0x4c, 0xfe,
+        0xad, 0x57, 0xcf, 0x83, 0x87, 0x63, 0x9d, 0x3b, 0x40,
+        0x96, 0xc5, 0x4f, 0x18, 0xf4, 0x00, 0x00, 0x00, 0x00
+    ];
+
+    let bob_scan_seckey: [u8; 32] = [
+        0xa8, 0x90, 0x54, 0xc9, 0x5b, 0xe3, 0xc3, 0x01,
+        0x56, 0x65, 0x74, 0xf2, 0xaa, 0x93, 0xad, 0xe0,
+        0x51, 0x85, 0x09, 0x03, 0xa6, 0x9c, 0xbd, 0xd1,
+        0xd4, 0x7e, 0xae, 0x26, 0x3d, 0x7b, 0xc0, 0x31
+    ];
+
+    let bob_spend_pubkey: [u8; 33] = [
+        0x02, 0xee, 0x97, 0xdf, 0x83, 0xb2, 0x54, 0x6a,
+        0xf5, 0xa7, 0xd0, 0x62, 0x15, 0xd9, 0x8b, 0xcb,
+        0x63, 0x7f, 0xe0, 0x5d, 0xd0, 0xfa, 0x37, 0x3b,
+        0xd8, 0x20, 0xe6, 0x64, 0xd3, 0x72, 0xde, 0x9a, 0x01
+    ];
+
+    let bob_address: [[u8; 33]; 2] = [
+        [
+            0x02, 0x15, 0x40, 0xae, 0xa8, 0x97, 0x54, 0x7a,
+            0xd4, 0x39, 0xb4, 0xe0, 0xf6, 0x09, 0xe5, 0xf0,
+            0xfa, 0x63, 0xde, 0x89, 0xab, 0x11, 0xed, 0xe3,
+            0x1e, 0x8c, 0xde, 0x4b, 0xe2, 0x19, 0x42, 0x5f, 0x23
+        ],
+        [
+            0x02, 0x3e, 0xff, 0xf8, 0x18, 0x51, 0x65, 0xea,
+            0x63, 0xa9, 0x92, 0xb3, 0x9f, 0x31, 0xd8, 0xfd,
+            0x8e, 0x0e, 0x64, 0xae, 0xf9, 0xd3, 0x88, 0x07,
+            0x34, 0x97, 0x37, 0x14, 0xa5, 0x3d, 0x83, 0x11, 0x8d
+        ]
+    ];
+
+    let carol_scan_key: [u8; 32] = [
+        0x04, 0xb2, 0xa4, 0x11, 0x63, 0x5c, 0x09, 0x77,
+        0x59, 0xaa, 0xcd, 0x0f, 0x00, 0x5a, 0x4c, 0x82,
+        0xc8, 0xc9, 0x28, 0x62, 0xc6, 0xfc, 0x28, 0x4b,
+        0x80, 0xb8, 0xef, 0xeb, 0xc2, 0x0c, 0x3d, 0x17
+    ];
+
+    let carol_address: [[u8; 33]; 2] = [
+        [
+            0x03, 0xbb, 0xc6, 0x3f, 0x12, 0x74, 0x5d, 0x3b,
+            0x9e, 0x9d, 0x24, 0xc6, 0xcd, 0x7a, 0x1e, 0xfe,
+            0xba, 0xd0, 0xa7, 0xf4, 0x69, 0x23, 0x2f, 0xbe,
+            0xcf, 0x31, 0xfb, 0xa7, 0xb4, 0xf7, 0xdd, 0xed, 0xa8
+        ],
+        [
+            0x03, 0x81, 0xeb, 0x9a, 0x9a, 0x9e, 0xc7, 0x39,
+            0xd5, 0x27, 0xc1, 0x63, 0x1b, 0x31, 0xb4, 0x21,
+            0x56, 0x6f, 0x5c, 0x2a, 0x47, 0xb4, 0xab, 0x5b,
+            0x1f, 0x6a, 0x68, 0x6d, 0xfb, 0x68, 0xea, 0xb7, 0x16
+        ]
+    ];
+
+    let address_amounts = ["1.0 BTC", "2.0 BTC", "3.0 BTC"];
+
+    let n_tx_outputs = 3;
+
+    let mut sp_addresses: [&[[u8; 33]; 2]; 3] = [&[[0; 33]; 2]; 3];
+
+    // Assign references to the addresses
+    sp_addresses[0] = &carol_address; // : 1.0 BTC
+    sp_addresses[1] = &bob_address;   // : 2.0 BTC
+    sp_addresses[2] = &carol_address;
+
+    let mut recipients = Vec::<SilentpaymentsRecipient>::new();
+
+    let mut tx_inputs = Vec::<XOnlyPublicKey>::new();
+
+    for i in 0..n_tx_outputs {
+        let recipient_index = i;
+
+        let recipient_scan_pubkey = PublicKey::from_slice(&sp_addresses[i][0]).unwrap();
+        let recipient_spend_pubkey = PublicKey::from_slice(&sp_addresses[i][1]).unwrap();
+
+        let silentpayment_recipient = SilentpaymentsRecipient::new(
+            &recipient_scan_pubkey, 
+            &recipient_spend_pubkey, 
+            recipient_index
+        );
+
+        recipients.push(silentpayment_recipient);
+    }
+
+    let recipients = recipients.as_slice();
+
+    let mut taproot_seckeys = Vec::<Keypair>::new();
+
+    for &key in sender_secret_keys.iter() {
+        let seckey: [u8; 32] = key;
+
+        let keypair = Keypair::from_seckey_slice(&secp, &seckey).unwrap();
+
+        taproot_seckeys.push(keypair);
+
+        tx_inputs.push(keypair.x_only_public_key().0);
+    }
+
+    let taproot_seckeys = taproot_seckeys.as_slice();
+
+    let mut tx_outputs: Vec<XOnlyPublicKey> = Vec::new();
+
+    let out_pubkeys = silentpayments_sender_create_outputs(
+        &secp, 
+        recipients,
+        &smallest_outpoint,
+        Some(taproot_seckeys),
+        None
+    ).unwrap();
+
+    println!("{}:", "Alice created the following outputs for Bob and Carol:");
+    for (i, out_pubkey)  in out_pubkeys.iter().enumerate() {
+        print!("\t{} : 0x", address_amounts[i]);
+        for byte in out_pubkey.serialize().iter().cloned() {
+            print!("{:02x}", byte);
+        }
+        println!();
+
+        tx_outputs.push(out_pubkey.clone());
+    }
+
+    let bob_scan_secretkey = SecretKey::from_slice(&bob_scan_seckey).unwrap();
+    let m: u32 = 1;
+
+    let label_tweak_result = silentpayments_recipient_create_label_tweak(&secp, &bob_scan_secretkey, m).unwrap();
+
+    let bob_spend_publickey = PublicKey::from_slice(&bob_spend_pubkey).unwrap();
+
+    let _labelled_spend_pubkey = silentpayments_recipient_create_labelled_spend_pubkey(
+        &secp,
+        &bob_spend_publickey,
+        &label_tweak_result.pubkey
+    ).unwrap();
+
+    let public_data: SilentpaymentsPublicData = SilentpaymentsPublicData::create(
+        &secp,
+        &smallest_outpoint,
+        Some(&tx_inputs),
+        None
+    ).unwrap();
+
+    let mut cache = LabelsCache {
+        entries_used: 0,
+        entries: [LabelCacheEntry {
+            label: [0; 33],
+            label_tweak: [0; 32]
+        }; 5]
+    };
+
+    cache.entries[0].label = label_tweak_result.pubkey.serialize();
+    cache.entries[0].label_tweak = label_tweak_result.label_tweak;
+    cache.entries_used += 1;
+
+    let _label_tweak = rust_secp256k1_silentpayments_label_lookup(
+        label_tweak_result.pubkey.serialize().as_ptr(),
+        &cache as *const LabelsCache as *const c_void
+    );
+
+    let tx_outputs_slice = tx_outputs.as_slice();
+
+    let bob_spend_publickey = PublicKey::from_slice(&bob_spend_pubkey).unwrap();
+
+    let found_output = silentpayments_recipient_scan_outputs(
+        &secp,
+        tx_outputs_slice,
+        &bob_scan_secretkey,
+        &public_data,
+        &bob_spend_publickey,
+        rust_secp256k1_silentpayments_label_lookup,
+        cache
+    ).unwrap();
+
+    println!();
+    println!("{} :", "Bob found the following outputs:");
+    for output in found_output.iter() {
+        println!("\t{}", output);
+    }
+
+    let light_client_data33 = public_data.serialize(&secp).unwrap();
+
+    let carol_public_data = SilentpaymentsPublicData::parse(&secp, &light_client_data33).unwrap();
+
+    let carol_scan_seckey = SecretKey::from_slice(&carol_scan_key).unwrap();
+
+    let shared_secret = carol_public_data.recipient_create_shared_secret(&secp, &carol_scan_seckey).unwrap();
+
+    let mut found: bool;
+    let mut k: u32 = 0;
+    let mut ser_found_outputs: Vec<XOnlyPublicKey> = Vec::new();
+
+    let carol_spend_pubkey = PublicKey::from_slice(&carol_address[1]).unwrap();
+
+    println!();
+
+    loop {
+
+        let potential_output = 
+            silentpayments_recipient_create_output_pubkey(&secp, &shared_secret, &carol_spend_pubkey, k).unwrap();
+
+        found = false;
+        for i in 0..n_tx_outputs {
+            if tx_outputs[i] == potential_output {
+                ser_found_outputs.push(potential_output);
+                found = true;
+                k += 1;
+                break;
+            }
+        }
+
+        if !found {
+            break;
+        }
+    }
+
+    println!("{}:", "Carol found the following outputs");
+    for output in ser_found_outputs.iter() {
+        print!("\t{}", "0x");
+        for byte in output.serialize().iter().cloned() {
+            print!("{:02x}", byte);
+        }
+        println!();
+    }
+}