Verify the CBTC deposit address locally

CHANGELOG.md

@@ -6,6 +6,22 @@ follows [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
 
+### Security
+
+- `cbtc::mint::get_bitcoin_address` no longer trusts the BitSafe API for the
+  deposit address. It derives the address locally from the attestor group key
+  that the crate pins for each network, and fails when the API returns a
+  different one. `get_deposit_account_status` gets the same check. A
+  compromised API, or a hijacked API domain, can no longer hand out an
+  address that the attestors do not control.
+
+### Changed
+
+- A new attestor key (a new DKG) needs a new release of this crate. Until
+  then, `get_bitcoin_address` fails with a mismatch error instead of
+  returning an address.
+- The crate depends on `bitcoin` 0.32 for the address derivation.
+
 ## [0.3.0] - 2026-10-21
 
 ### Fixed

Cargo.toml

@@ -20,6 +20,7 @@ uninlined_format_args = "allow"
 [dependencies]
 alloy-primitives = { version = "1.7.3" }
 alloy-sol-types = { version = "1.7.3" }
+bitcoin = { version = "0.32.102" }
 common = { git = "https://github.com/DLC-link/canton-lib", tag = "v0.12.0" }
 ledger = { git = "https://github.com/DLC-link/canton-lib", tag = "v0.12.0" }
 registry = { git = "https://github.com/DLC-link/canton-lib", tag = "v0.12.0" }

README.md

@@ -104,6 +104,8 @@ async fn main() -> Result<(), String> {
         credential_cids: credential_cids.clone(),
     })
     .await?;
+    // The lib checks the API's address against a local derivation from the
+    // attestor key it pins, and fails on a mismatch.
     let btc_address = mint::get_bitcoin_address(network, &account).await?;
     println!("Send BTC to {btc_address}");