Altair consensus changes and refactors (#2279)

## Proposed Changes

Implement the consensus changes necessary for the upcoming Altair hard fork.

## Additional Info

This is quite a heavy refactor, with pivotal types like the `BeaconState` and `BeaconBlock` changing from structs to enums. This ripples through the whole codebase with field accesses changing to methods, e.g. `state.slot` => `state.slot()`.


Co-authored-by: realbigsean <seananderson33@gmail.com>

crypto/bls/src/impls/blst.rs

@@ -153,7 +153,19 @@ impl PartialEq for BlstAggregatePublicKey {
     }
 }
 
-impl TAggregatePublicKey for BlstAggregatePublicKey {}
+impl TAggregatePublicKey<blst_core::PublicKey> for BlstAggregatePublicKey {
+    fn to_public_key(&self) -> GenericPublicKey<blst_core::PublicKey> {
+        GenericPublicKey::from_point(self.0.to_public_key())
+    }
+
+    fn aggregate(pubkeys: &[GenericPublicKey<blst_core::PublicKey>]) -> Result<Self, Error> {
+        let pubkey_refs = pubkeys.iter().map(|pk| pk.point()).collect::<Vec<_>>();
+
+        // Public keys have already been checked for subgroup and infinity
+        let agg_pub = blst_core::AggregatePublicKey::aggregate(&pubkey_refs, false)?;
+        Ok(BlstAggregatePublicKey(agg_pub))
+    }
+}
 
 impl TSignature<blst_core::PublicKey> for blst_core::Signature {
     fn serialize(&self) -> [u8; SIGNATURE_BYTES_LEN] {

crypto/bls/src/impls/fake_crypto.rs

@@ -6,6 +6,7 @@ use crate::{
     generic_signature::{TSignature, SIGNATURE_BYTES_LEN},
     Error, Hash256, ZeroizeHash, INFINITY_PUBLIC_KEY, INFINITY_SIGNATURE,
 };
+
 /// Provides the externally-facing, core BLS types.
 pub mod types {
     pub use super::verify_signature_sets;
@@ -63,7 +64,15 @@ impl PartialEq for PublicKey {
 #[derive(Clone)]
 pub struct AggregatePublicKey([u8; PUBLIC_KEY_BYTES_LEN]);
 
-impl TAggregatePublicKey for AggregatePublicKey {}
+impl TAggregatePublicKey<PublicKey> for AggregatePublicKey {
+    fn to_public_key(&self) -> GenericPublicKey<PublicKey> {
+        GenericPublicKey::from_point(PublicKey(self.0))
+    }
+
+    fn aggregate(_pubkeys: &[GenericPublicKey<PublicKey>]) -> Result<Self, Error> {
+        Ok(Self(INFINITY_PUBLIC_KEY))
+    }
+}
 
 impl Eq for AggregatePublicKey {}
 

crypto/bls/src/impls/milagro.rs

@@ -86,7 +86,18 @@ impl TPublicKey for milagro::PublicKey {
     }
 }
 
-impl TAggregatePublicKey for milagro::AggregatePublicKey {}
+impl TAggregatePublicKey<milagro::PublicKey> for milagro::AggregatePublicKey {
+    fn to_public_key(&self) -> GenericPublicKey<milagro::PublicKey> {
+        GenericPublicKey::from_point(milagro::PublicKey {
+            point: self.point.clone(),
+        })
+    }
+
+    fn aggregate(pubkeys: &[GenericPublicKey<milagro::PublicKey>]) -> Result<Self, Error> {
+        let pubkey_refs = pubkeys.iter().map(|pk| pk.point()).collect::<Vec<_>>();
+        Ok(milagro::AggregatePublicKey::aggregate(&pubkey_refs)?)
+    }
+}
 
 impl TSignature<milagro::PublicKey> for milagro::Signature {
     fn serialize(&self) -> [u8; SIGNATURE_BYTES_LEN] {