Create a dedicated crate for the DKG (#141)

* Add dkg crate

* Remove F_len and G_len

They're generally no longer used.

* Replace hash_to_vec with a provided method around associated type H: Digest

Part of trying to minimize this trait so it can be moved elsewhere. Vec, 
which isn't std, may have been a blocker.

* Encrypt secret shares within the FROST library

Reduces requirements on callers in order to be correct.

* Update usage of Zeroize within FROST

* Inline functions in key_gen

There was no reason to have them separated as they were. sign probably 
has the same statement available, yet that isn't the focus right now.

* Add a ciphersuite package which provides hash_to_F

* Set the Ciphersuite version to something valid

* Have ed448 export Scalar/FieldElement/Point at the top level

* Move FROST over to Ciphersuite

* Correct usage of ff in ciphersuite

* Correct documentation handling

* Move Schnorr signatures to their own crate

* Remove unused feature from schnorr

* Fix Schnorr tests

* Split DKG into a separate crate

* Add serialize to Commitments and SecretShare

Helper for buf = vec![]; .write(buf).unwrap(); buf

* Move FROST over to the new dkg crate

* Update Monero lib to latest FROST

* Correct ethereum's usage of features

* Add serialize to GeneratorProof

* Add serialize helper function to FROST

* Rename AddendumSerialize to WriteAddendum

* Update processor

* Slight fix to processor

crypto/ciphersuite/src/ed448.rs

@@ -0,0 +1,67 @@
+use zeroize::Zeroize;
+
+use digest::{
+  typenum::U114, core_api::BlockSizeUser, Update, Output, OutputSizeUser, FixedOutput,
+  ExtendableOutput, XofReader, HashMarker, Digest,
+};
+use sha3::Shake256;
+
+use group::Group;
+use minimal_ed448::{scalar::Scalar, point::Point};
+
+use crate::Ciphersuite;
+
+// Re-define Shake256 as a traditional Digest to meet API expectations
+#[derive(Clone, Default)]
+pub struct Shake256_114(Shake256);
+impl BlockSizeUser for Shake256_114 {
+  type BlockSize = <Shake256 as BlockSizeUser>::BlockSize;
+  fn block_size() -> usize {
+    Shake256::block_size()
+  }
+}
+impl OutputSizeUser for Shake256_114 {
+  type OutputSize = U114;
+  fn output_size() -> usize {
+    114
+  }
+}
+impl Update for Shake256_114 {
+  fn update(&mut self, data: &[u8]) {
+    self.0.update(data);
+  }
+  fn chain(mut self, data: impl AsRef<[u8]>) -> Self {
+    Update::update(&mut self, data.as_ref());
+    self
+  }
+}
+impl FixedOutput for Shake256_114 {
+  fn finalize_fixed(self) -> Output<Self> {
+    let mut res = Default::default();
+    FixedOutput::finalize_into(self, &mut res);
+    res
+  }
+  fn finalize_into(self, out: &mut Output<Self>) {
+    let mut reader = self.0.finalize_xof();
+    reader.read(out);
+  }
+}
+impl HashMarker for Shake256_114 {}
+
+#[derive(Clone, Copy, PartialEq, Eq, Debug, Zeroize)]
+pub struct Ed448;
+impl Ciphersuite for Ed448 {
+  type F = Scalar;
+  type G = Point;
+  type H = Shake256_114;
+
+  const ID: &'static [u8] = b"ed448";
+
+  fn generator() -> Self::G {
+    Point::generator()
+  }
+
+  fn hash_to_F(dst: &[u8], data: &[u8]) -> Self::F {
+    Scalar::wide_reduce(Self::H::digest(&[dst, data].concat()).as_ref().try_into().unwrap())
+  }
+}