[offchain] Support for sign & verify for crypto keys (#3023)

* Implement sign & verify.

* Use phrases and password.

* Sign & verify with authority keys.

* Fix tests.

* WiP

* WiP

* Allow the caller to decide on 'CryptoKind'.

* Remove TODO.

* Make seed private back.

* Fix non-std build and bump version.

* Use Into<u32> instead of asses.

* Add missing typedef.

substrate/core/service/src/config.rs

@@ -16,12 +16,14 @@
 
 //! Service configuration.
 
-use std::{path::PathBuf, net::SocketAddr};
-use transaction_pool;
-use crate::chain_spec::ChainSpec;
 pub use client::ExecutionStrategies;
 pub use client_db::PruningMode;
 pub use network::config::{ExtTransport, NetworkConfiguration, Roles};
+
+use std::{path::PathBuf, net::SocketAddr};
+use transaction_pool;
+use crate::chain_spec::ChainSpec;
+use primitives::crypto::Protected;
 use runtime_primitives::BuildStorage;
 use serde::{Serialize, de::DeserializeOwned};
 use target_info::Target;
@@ -86,7 +88,7 @@ pub struct Configuration<C, G: Serialize + DeserializeOwned + BuildStorage> {
 	/// Disable GRANDPA when running in validator mode
 	pub disable_grandpa: bool,
 	/// Node keystore's password
-	pub password: String,
+	pub password: Protected<String>,
 }
 
 impl<C: Default, G: Serialize + DeserializeOwned + BuildStorage> Configuration<C, G> {
@@ -120,7 +122,7 @@ impl<C: Default, G: Serialize + DeserializeOwned + BuildStorage> Configuration<C
 			offchain_worker: Default::default(),
 			force_authoring: false,
 			disable_grandpa: false,
-			password: "".to_string(),
+			password: "".to_string().into(),
 		};
 		configuration.network.boot_nodes = configuration.chain_spec.boot_nodes().to_vec();