Consolidate crypto functionality in ethcore-crypto. (#8432)

* Consolidate crypto functionality in `ethcore-crypto`.

- Move `ecdh`/`ecies` modules to `ethkey`.
- Refactor `ethcore-crypto` to use file per module.
- Replace `subtle` with `ethcore_crypto::is_equal`.
- Add `aes_gcm` module to `ethcore-crypto`.

* Rename `aes::{encrypt,decrypt,decrypt_cbc}` ...

... to `aes::{encrypt_128_ctr,decrypt_128_ctr,decrypt_128_cbc}`.

ethcore/crypto/src/hmac.rs

@@ -0,0 +1,89 @@
+// Copyright 2018 Parity Technologies (UK) Ltd.
+// This file is part of Parity.
+
+// Parity is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity.  If not, see <http://www.gnu.org/licenses/>.
+
+use digest;
+use ring::digest::{SHA256, SHA512};
+use ring::hmac::{self, SigningContext};
+use std::marker::PhantomData;
+use std::ops::Deref;
+
+/// HMAC signature.
+pub struct Signature<T>(hmac::Signature, PhantomData<T>);
+
+impl<T> Deref for Signature<T> {
+	type Target = [u8];
+	fn deref(&self) -> &Self::Target {
+		self.0.as_ref()
+	}
+}
+
+/// HMAC signing key.
+pub struct SigKey<T>(hmac::SigningKey, PhantomData<T>);
+
+impl SigKey<digest::Sha256> {
+	pub fn sha256(key: &[u8]) -> SigKey<digest::Sha256> {
+		SigKey(hmac::SigningKey::new(&SHA256, key), PhantomData)
+	}
+}
+
+impl SigKey<digest::Sha512> {
+	pub fn sha512(key: &[u8]) -> SigKey<digest::Sha512> {
+		SigKey(hmac::SigningKey::new(&SHA512, key), PhantomData)
+	}
+}
+
+/// Compute HMAC signature of `data`.
+pub fn sign<T>(k: &SigKey<T>, data: &[u8]) -> Signature<T> {
+	Signature(hmac::sign(&k.0, data), PhantomData)
+}
+
+/// Stateful HMAC computation.
+pub struct Signer<T>(SigningContext, PhantomData<T>);
+
+impl<T> Signer<T> {
+	pub fn with(key: &SigKey<T>) -> Signer<T> {
+		Signer(hmac::SigningContext::with_key(&key.0), PhantomData)
+	}
+
+	pub fn update(&mut self, data: &[u8]) {
+		self.0.update(data)
+	}
+
+	pub fn sign(self) -> Signature<T> {
+		Signature(self.0.sign(), PhantomData)
+	}
+}
+
+/// HMAC signature verification key.
+pub struct VerifyKey<T>(hmac::VerificationKey, PhantomData<T>);
+
+impl VerifyKey<digest::Sha256> {
+	pub fn sha256(key: &[u8]) -> VerifyKey<digest::Sha256> {
+		VerifyKey(hmac::VerificationKey::new(&SHA256, key), PhantomData)
+	}
+}
+
+impl VerifyKey<digest::Sha512> {
+	pub fn sha512(key: &[u8]) -> VerifyKey<digest::Sha512> {
+		VerifyKey(hmac::VerificationKey::new(&SHA512, key), PhantomData)
+	}
+}
+
+/// Verify HMAC signature of `data`.
+pub fn verify<T>(k: &VerifyKey<T>, data: &[u8], sig: &[u8]) -> bool {
+	hmac::verify(&k.0, data, sig).is_ok()
+}
+