As discussed in the tendermint-dev call, there are a few places where we use some amino-specifics in the communication with the KMS. It might be worth investigating if we could/should do without them:

in secret connection:

• the interface crypto.PubKey (used in authSigMessage) currently always is a ed25519 key:

  tendermint/p2p/conn/secret_connection.go

  Lines 298 to 301 in c086d0a

  	type authSigMessage struct {
  	Key crypto.PubKey
  	Sig []byte
  	}

• the keys shared via shareEphPubKey are send as raw bytes but they are length prefixed "twice" (once for the total message, once for the length of the byte slice); we probably do not need that (use marshalbinarybare instead):

  tendermint/p2p/conn/secret_connection.go

  Lines 212 to 222 in c086d0a

  	var trs, _ = cmn.Parallel(
  	func(_ int) (val interface{}, err error, abort bool) {
  	var _, err1 = cdc.MarshalBinaryLengthPrefixedWriter(conn, locEphPub)
  	if err1 != nil {
  	return nil, err1, true // abort
  	}
  	return nil, nil, false
  	},
  	func(_ int) (val interface{}, err error, abort bool) {
  	var _remEphPub [32]byte
  	var _, err2 = cdc.UnmarshalBinaryLengthPrefixedReader(conn, &_remEphPub, 1024*1024) // TODO

other usages of interfaces:

• PubKeyMsg contains a crypto.PubKey (again only ed25519 is currently used AFAIK):

  tendermint/privval/remote_signer.go

  Lines 196 to 198 in c086d0a

  	type PubKeyMsg struct {
  	PubKey crypto.PubKey
  	}

• RemoteSignerMsg is an interface; it only has a few implementations though:

  tendermint/privval/remote_signer.go

  Lines 180 to 190 in c086d0a

  	type RemoteSignerMsg interface{}
  	func RegisterRemoteSignerMsg(cdc *amino.Codec) {
  	cdc.RegisterInterface((*RemoteSignerMsg)(nil), nil)
  	cdc.RegisterConcrete(&PubKeyMsg{}, "tendermint/remotesigner/PubKeyMsg", nil)
  	cdc.RegisterConcrete(&SignVoteRequest{}, "tendermint/remotesigner/SignVoteRequest", nil)
  	cdc.RegisterConcrete(&SignedVoteResponse{}, "tendermint/remotesigner/SignedVoteResponse", nil)
  	cdc.RegisterConcrete(&SignProposalRequest{}, "tendermint/remotesigner/SignProposalRequest", nil)
  	cdc.RegisterConcrete(&SignedProposalResponse{}, "tendermint/remotesigner/SignedProposalResponse", nil)
  	cdc.RegisterConcrete(&SignHeartbeatRequest{}, "tendermint/remotesigner/SignHeartbeatRequest", nil)
  	cdc.RegisterConcrete(&SignedHeartbeatResponse{}, "tendermint/remotesigner/SignedHeartbeatResponse", nil)

  (this could be replaced by oneof IMHO; currently not supported by amino though)

cc @ValarDragon @ebuchman

ref tendermint/tmkms#91