diff --git a/substrate/core/primitives/src/crypto.rs b/substrate/core/primitives/src/crypto.rs
index b7c70e6224..6e46793432 100644
--- a/substrate/core/primitives/src/crypto.rs
+++ b/substrate/core/primitives/src/crypto.rs
@@ -790,6 +790,9 @@ pub trait Pair: CryptoType + Sized + Clone + Send + Sync + 'static {
 		root.derive(path, Some(seed)).map_err(|_| SecretStringError::InvalidPath)
 	}
 
+	/// Interprets the string `s` in order to generate a key pair.
+	///
+	/// See [`from_string_with_seed`](Self::from_string_with_seed) for more extensive documentation.
 	fn from_string(s: &str, password_override: Option<&str>) -> Result<Self, SecretStringError> {
 		Self::from_string_with_seed(s, password_override).map(|x| x.0)
 	}
diff --git a/substrate/core/sr-primitives/src/lib.rs b/substrate/core/sr-primitives/src/lib.rs
index 624e224ef1..4341e3543a 100644
--- a/substrate/core/sr-primitives/src/lib.rs
+++ b/substrate/core/sr-primitives/src/lib.rs
@@ -255,18 +255,39 @@ impl From<ed25519::Public> for MultiSigner {
 	}
 }
 
+impl TryFrom<MultiSigner> for ed25519::Public {
+	type Error = ();
+	fn try_from(m: MultiSigner) -> Result<Self, Self::Error> {
+		if let MultiSigner::Ed25519(x) = m { Ok(x) } else { Err(()) }
+	}
+}
+
 impl From<sr25519::Public> for MultiSigner {
 	fn from(x: sr25519::Public) -> Self {
 		MultiSigner::Sr25519(x)
 	}
 }
 
+impl TryFrom<MultiSigner> for sr25519::Public {
+	type Error = ();
+	fn try_from(m: MultiSigner) -> Result<Self, Self::Error> {
+		if let MultiSigner::Sr25519(x) = m { Ok(x) } else { Err(()) }
+	}
+}
+
 impl From<ecdsa::Public> for MultiSigner {
 	fn from(x: ecdsa::Public) -> Self {
 		MultiSigner::Ecdsa(x)
 	}
 }
 
+impl TryFrom<MultiSigner> for ecdsa::Public {
+	type Error = ();
+	fn try_from(m: MultiSigner) -> Result<Self, Self::Error> {
+		if let MultiSigner::Ecdsa(x) = m { Ok(x) } else { Err(()) }
+	}
+}
+
 #[cfg(feature = "std")]
 impl std::fmt::Display for MultiSigner {
 	fn fmt(&self, fmt: &mut std::fmt::Formatter) -> std::fmt::Result {
diff --git a/substrate/node/runtime/src/lib.rs b/substrate/node/runtime/src/lib.rs
index fefc1144ac..3b72ff40fa 100644
--- a/substrate/node/runtime/src/lib.rs
+++ b/substrate/node/runtime/src/lib.rs
@@ -42,7 +42,7 @@ use sr_primitives::curve::PiecewiseLinear;
 use sr_primitives::transaction_validity::TransactionValidity;
 use sr_primitives::weights::Weight;
 use sr_primitives::traits::{
-	BlakeTwo256, Block as BlockT, NumberFor, StaticLookup,
+	self, BlakeTwo256, Block as BlockT, NumberFor, StaticLookup, SaturatedConversion,
 };
 use version::RuntimeVersion;
 #[cfg(any(feature = "std", test))]
@@ -459,6 +459,36 @@ impl finality_tracker::Trait for Runtime {
 	type ReportLatency = ReportLatency;
 }
 
+impl system::offchain::CreateTransaction<Runtime, UncheckedExtrinsic> for Runtime {
+	type Public = <Signature as traits::Verify>::Signer;
+	type Signature = Signature;
+
+	fn create_transaction<F: system::offchain::Signer<Self::Public, Self::Signature>>(
+		call: Call,
+		public: Self::Public,
+		account: AccountId,
+		index: Index,
+	) -> Option<(Call, <UncheckedExtrinsic as traits::Extrinsic>::SignaturePayload)> {
+		let period = 1 << 8;
+		let current_block = System::block_number().saturated_into::<u64>();
+		let tip = 0;
+		let extra: SignedExtra = (
+			system::CheckVersion::<Runtime>::new(),
+			system::CheckGenesis::<Runtime>::new(),
+			system::CheckEra::<Runtime>::from(generic::Era::mortal(period, current_block)),
+			system::CheckNonce::<Runtime>::from(index),
+			system::CheckWeight::<Runtime>::new(),
+			transaction_payment::ChargeTransactionPayment::<Runtime>::from(tip),
+			Default::default(),
+		);
+		let raw_payload = SignedPayload::new(call, extra).ok()?;
+		let signature = F::sign(public, &raw_payload)?;
+		let address = Indices::unlookup(account);
+		let (call, extra, _) = raw_payload.deconstruct();
+		Some((call, (address, signature, extra)))
+	}
+}
+
 construct_runtime!(
 	pub enum Runtime where
 		Block = Block,
@@ -669,3 +699,24 @@ impl_runtime_apis! {
 		}
 	}
 }
+#[cfg(test)]
+mod tests {
+	use super::*;
+	use system::offchain::SubmitSignedTransaction;
+
+	fn is_submit_signed_transaction<T>(_arg: T) where
+		T: SubmitSignedTransaction<
+			Runtime,
+			Call,
+			Extrinsic=UncheckedExtrinsic,
+			CreateTransaction=Runtime,
+			Signer=ImOnlineId,
+		>,
+	{}
+
+	#[test]
+	fn validate_bounds() {
+		let x = SubmitTransaction::default();
+		is_submit_signed_transaction(x);
+	}
+}
diff --git a/substrate/srml/im-online/src/lib.rs b/substrate/srml/im-online/src/lib.rs
index 202507bef9..82b866d32b 100644
--- a/substrate/srml/im-online/src/lib.rs
+++ b/substrate/srml/im-online/src/lib.rs
@@ -96,12 +96,6 @@ pub mod sr25519 {
 	mod app_sr25519 {
 		use app_crypto::{app_crypto, key_types::IM_ONLINE, sr25519};
 		app_crypto!(sr25519, IM_ONLINE);
-
-		impl From<Signature> for sr_primitives::AnySignature {
-			fn from(sig: Signature) -> Self {
-				sr25519::Signature::from(sig).into()
-			}
-		}
 	}
 
 	/// An i'm online keypair using sr25519 as its crypto.
@@ -119,12 +113,6 @@ pub mod ed25519 {
 	mod app_ed25519 {
 		use app_crypto::{app_crypto, key_types::IM_ONLINE, ed25519};
 		app_crypto!(ed25519, IM_ONLINE);
-
-		impl From<Signature> for sr_primitives::AnySignature {
-			fn from(sig: Signature) -> Self {
-				ed25519::Signature::from(sig).into()
-			}
-		}
 	}
 
 	/// An i'm online keypair using ed25519 as its crypto.
diff --git a/substrate/srml/system/src/offchain.rs b/substrate/srml/system/src/offchain.rs
index 468c88af39..11f7e234f7 100644
--- a/substrate/srml/system/src/offchain.rs
+++ b/substrate/srml/system/src/offchain.rs
@@ -17,8 +17,8 @@
 //! Module helpers for offchain calls.
 
 use codec::Encode;
-use sr_primitives::app_crypto::RuntimeAppPublic;
-use sr_primitives::traits::Extrinsic as ExtrinsicT;
+use sr_primitives::app_crypto::{self, RuntimeAppPublic};
+use sr_primitives::traits::{Extrinsic as ExtrinsicT, IdentifyAccount};
 
 /// A trait responsible for signing a payload using given account.
 pub trait Signer<Public, Signature> {
@@ -28,17 +28,96 @@ pub trait Signer<Public, Signature> {
 	fn sign<Payload: Encode>(public: Public, payload: &Payload) -> Option<Signature>;
 }
 
+/// A `Signer` implementation for any `AppPublic` type.
+///
+/// This implementation additionaly supports conversion to/from multi-signature/multi-signer
+/// wrappers.
+/// If the wrapped crypto doesn't match `AppPublic`s crypto `None` is returned.
 impl<Public, Signature, AppPublic> Signer<Public, Signature> for AppPublic where
-	AppPublic: RuntimeAppPublic + From<Public>,
-	AppPublic::Signature: Into<Signature>,
+	AppPublic: RuntimeAppPublic
+		+ app_crypto::AppPublic
+		+ From<<AppPublic as app_crypto::AppPublic>::Generic>,
+	<AppPublic as RuntimeAppPublic>::Signature: app_crypto::AppSignature,
+	Signature: From<
+		<<AppPublic as RuntimeAppPublic>::Signature as app_crypto::AppSignature>::Generic
+	>,
+	Public: rstd::convert::TryInto<<AppPublic as app_crypto::AppPublic>::Generic>
 {
 	fn sign<Payload: Encode>(public: Public, raw_payload: &Payload) -> Option<Signature> {
 		raw_payload.using_encoded(|payload| {
-			AppPublic::from(public).sign(&payload).map(Into::into)
+			let public = public.try_into().ok()?;
+			AppPublic::from(public).sign(&payload)
+				.map(
+					<<AppPublic as RuntimeAppPublic>::Signature as app_crypto::AppSignature>
+					 ::Generic::from
+				)
+				.map(Signature::from)
 		})
 	}
 }
 
+/// Creates runtime-specific signed transaction.
+pub trait CreateTransaction<T: crate::Trait, Extrinsic: ExtrinsicT> {
+	/// A `Public` key representing a particular `AccountId`.
+	type Public;
+	/// A `Signature` generated by the `Signer`.
+	type Signature;
+
+	/// Attempt to create signed extrinsic data that encodes call from given account.
+	///
+	/// Runtime implementation is free to construct the payload to sign and the signature
+	/// in any way it wants.
+	/// Returns `None` if signed extrinsic could not be created (either because signing failed
+	/// or because of any other runtime-specific reason).
+	fn create_transaction<F: Signer<Self::Public, Self::Signature>>(
+		call: Extrinsic::Call,
+		public: Self::Public,
+		account: T::AccountId,
+		nonce: T::Index,
+	) -> Option<(Extrinsic::Call, Extrinsic::SignaturePayload)>;
+}
+
+type PublicOf<T, Call, X> = <
+	<X as SubmitSignedTransaction<T, Call>>::CreateTransaction as CreateTransaction<
+		T,
+		<X as SubmitSignedTransaction<T, Call>>::Extrinsic,
+	>
+>::Public;
+
+/// A trait to sign and submit transactions in offchain calls.
+pub trait SubmitSignedTransaction<T: crate::Trait, Call>
+where
+	PublicOf<T, Call, Self>: IdentifyAccount<AccountId=T::AccountId> + Clone,
+{
+	/// Unchecked extrinsic type.
+	type Extrinsic: ExtrinsicT<Call=Call> + codec::Encode;
+
+	/// A runtime-specific type to produce signed data for the extrinsic.
+	type CreateTransaction: CreateTransaction<T, Self::Extrinsic>;
+
+	/// A type used to sign transactions created using `CreateTransaction`.
+	type Signer: Signer<
+		PublicOf<T, Call, Self>,
+		<Self::CreateTransaction as CreateTransaction<T, Self::Extrinsic>>::Signature,
+	>;
+
+	/// Sign given call and submit it to the transaction pool.
+	///
+	/// Returns `Ok` if the transaction was submitted correctly
+	/// and `Err` if the key for given `id` was not found or the
+	/// transaction was rejected from the pool.
+	fn sign_and_submit(call: impl Into<Call>, public: PublicOf<T, Call, Self>) -> Result<(), ()> {
+		let call = call.into();
+		let id = public.clone().into_account();
+		let expected = <crate::Module<T>>::account_nonce(&id);
+		let (call, signature_data) = Self::CreateTransaction
+			::create_transaction::<Self::Signer>(call, public, id, expected)
+			.ok_or(())?;
+		let xt = Self::Extrinsic::new(call, Some(signature_data)).ok_or(())?;
+		runtime_io::submit_transaction(xt.encode())
+	}
+}
+
 /// A trait to submit unsigned transactions in offchain calls.
 pub trait SubmitUnsignedTransaction<T: crate::Trait, Call> {
 	/// Unchecked extrinsic type.
@@ -67,6 +146,19 @@ impl<S, C, E> Default for TransactionSubmitter<S, C, E> {
 	}
 }
 
+/// A blanket implementation to simplify creation of transaction signer & submitter in the runtime.
+impl<T, E, S, C, Call> SubmitSignedTransaction<T, Call> for TransactionSubmitter<S, C, E> where
+	T: crate::Trait,
+	C: CreateTransaction<T, E>,
+	S: Signer<<C as CreateTransaction<T, E>>::Public, <C as CreateTransaction<T, E>>::Signature>,
+	E: ExtrinsicT<Call=Call> + codec::Encode,
+	<C as CreateTransaction<T, E>>::Public: IdentifyAccount<AccountId=T::AccountId> + Clone,
+{
+	type Extrinsic = E;
+	type CreateTransaction = C;
+	type Signer = S;
+}
+
 /// A blanket impl to use the same submitter for usigned transactions as well.
 impl<T, E, S, C, Call> SubmitUnsignedTransaction<T, Call> for TransactionSubmitter<S, C, E> where
 	T: crate::Trait,