Encryption support for the statement store (#14440)

* Added ECIES encryption

* tweaks

* fmt

* Make clippy happy

* Use local keystore

* qed

substrate/primitives/statement-store/src/lib.rs

@@ -49,6 +49,8 @@ pub use store_api::{
 	Error, NetworkPriority, Result, StatementSource, StatementStore, SubmitResult,
 };
 
+#[cfg(feature = "std")]
+mod ecies;
 pub mod runtime_api;
 #[cfg(feature = "std")]
 mod store_api;
@@ -61,12 +63,17 @@ mod sr25519 {
 	pub type Public = app_sr25519::Public;
 }
 
-mod ed25519 {
+/// Statement-store specific ed25519 crypto primitives.
+pub mod ed25519 {
 	mod app_ed25519 {
 		use sp_application_crypto::{app_crypto, ed25519, key_types::STATEMENT};
 		app_crypto!(ed25519, STATEMENT);
 	}
+	/// Statement-store specific ed25519 public key.
 	pub type Public = app_ed25519::Public;
+	/// Statement-store specific ed25519 key pair.
+	#[cfg(feature = "std")]
+	pub type Pair = app_ed25519::Pair;
 }
 
 mod ecdsa {
@@ -507,6 +514,28 @@ impl Statement {
 		}
 		output
 	}
+
+	/// Encrypt give data with given key and store both in the statements.
+	#[cfg(feature = "std")]
+	pub fn encrypt(
+		&mut self,
+		data: &[u8],
+		key: &sp_core::ed25519::Public,
+	) -> core::result::Result<(), ecies::Error> {
+		let encrypted = ecies::encrypt_ed25519(key, data)?;
+		self.data = Some(encrypted);
+		self.decryption_key = Some((*key).into());
+		Ok(())
+	}
+
+	/// Decrypt data (if any) with the given private key.
+	#[cfg(feature = "std")]
+	pub fn decrypt_private(
+		&self,
+		key: &sp_core::ed25519::Pair,
+	) -> core::result::Result<Option<Vec<u8>>, ecies::Error> {
+		self.data.as_ref().map(|d| ecies::decrypt_ed25519(key, d)).transpose()
+	}
 }
 
 #[cfg(test)]
@@ -615,4 +644,18 @@ mod test {
 		statement.remove_proof();
 		assert_eq!(statement.verify_signature(), SignatureVerificationResult::NoSignature);
 	}
+
+	#[test]
+	fn encrypt_decrypt() {
+		let mut statement = Statement::new();
+		let (pair, _) = sp_core::ed25519::Pair::generate();
+		let plain = b"test data".to_vec();
+
+		//let sr25519_kp = sp_core::sr25519::Pair::from_string("//Alice", None).unwrap();
+		statement.encrypt(&plain, &pair.public()).unwrap();
+		assert_ne!(plain.as_slice(), statement.data().unwrap().as_slice());
+
+		let decrypted = statement.decrypt_private(&pair).unwrap();
+		assert_eq!(decrypted, Some(plain));
+	}
 }