Merge #55: Export slip77 module

cd4217f Export slip77 module (Leonardo Comandini)
cfaa1c5 slip77: port test from rust-elements (Leonardo Comandini)

Pull request description:

  Following #54

  Also ports a test from rust-elements

ACKs for top commit:
  apoelstra:
    ACK cd4217f

Tree-SHA512: c348615aaa6a4f5ae1465f8f9f642f0006a6b829b15f4e9406e3023190e2aeffbe10cb2b134452e546f38bf6ca88e4572dee56428224876305ec1870a8f8f249

Author: apoelstra

src/confidential/slip77.rs

@@ -139,6 +139,22 @@ mod tests {
         );
     }
 
+    #[test]
+    fn slip77_from_rust_elements() {
+        // taken from rust-elements
+        let mbk = MasterBlindingKey::from_seed(&unhex("731e9b42eb9774f8a6b51af35a06f6ef1cdb6cf04402163ceacf0c8bace2831a"));
+        assert_eq!(
+            mbk.as_bytes(),
+            &unhex("c2f338e32ad1a2bd9cac569e67728163bf4c326a1770ec2293ba65548a581e97")[..]
+        );
+
+        let spk = elements::Script::from_str("a914afa92d77cd3541b443771649572db096cf49bf8c87").unwrap();
+        let expected = secp256k1_zkp::SecretKey::from_slice(&unhex(
+            "02b067c374bb56c54c016fae29218c000ada60f81ef45b4aeebbeb24931bb8bc"
+        )).unwrap();
+        assert_eq!(mbk.blinding_private_key(&spk), expected);
+    }
+
     #[test]
     fn local_test_elements_22_0() {
         // Local test on elements 22.0

src/lib.rs

@@ -148,6 +148,7 @@ use elements::secp256k1_zkp::Secp256k1;
 use elements::{locktime, opcodes, script, secp256k1_zkp};
 
 pub use crate::confidential::Descriptor as ConfidentialDescriptor;
+pub use crate::confidential::slip77;
 pub use crate::descriptor::{DefiniteDescriptorKey, Descriptor, DescriptorPublicKey};
 pub use crate::extensions::{CovenantExt, Extension, NoExt, TxEnv};
 pub use crate::interpreter::Interpreter;