adds distributed public key check

packages/binary/drng/subtypes/collectiveBeacon/collective_beacon.go

 package collectiveBeacon
 
 import (
+	"bytes"
 	"crypto/sha512"
 	"errors"
 
@@ -47,6 +48,10 @@ func VerifyCollectiveBeacon(state *state.State, data *events.CollectiveBeaconEve
 		return err
 	}
 
+	if !bytes.Equal(data.Dpk, state.Committee().DistributedPK) {
+		return errors.New("Distributed Public Key does not match")
+	}
+
 	if err := verifySignature(data); err != nil {
 		return err
 	}