diff --git a/proto/mf.proto b/proto/mf.proto
index 1e261a3..23a8e19 100644
--- a/proto/mf.proto
+++ b/proto/mf.proto
@@ -11,45 +11,45 @@ message MFFile {
     }
 
     // required mffile root attributes 1xx
-    Version version = 101;
-    bytes innerMessage = 102;
+    required Version version = 101;
+    required bytes innerMessage = 102;
     // these are used solely to detect corruption/truncation
     // and not for cryptographic integrity.
-    uint64 size = 103;
-    bytes sha256 = 104;
+    required uint64 size = 103;
+    required bytes sha256 = 104;
 
     // 2xx for optional manifest root attributes
     // think we might use gosignify instead of gpg:
     // github.com/frankbraun/gosignify
 
     //detached signature, ascii or binary
-    optional bytes signature = 201;
+    bytes signature = 201;
     //full GPG key id
-    optional bytes signer = 202;
+    bytes signer = 202;
     //full GPG signing public key, ascii or binary
-    optional bytes signingPubKey = 203;
+    bytes signingPubKey = 203;
 }
 
 message MFFilePath {
     // required attributes:
-    string path = 101;
-    uint64 size = 102;
+    required string path = 101;
+    required uint64 size = 102;
 
     // gotta have at least one:
-    repeated MFFileChecksum hashes = 201;
+    required repeated MFFileChecksum hashes = 201;
 
     // optional per-file metadata
-    optional string mimeType = 301;
-    optional google.protobuf.Timestamp mtime = 302;
-    optional google.protobuf.Timestamp ctime = 303;
-    optional google.protobuf.Timestamp atime = 304;
+    string mimeType = 301;
+    google.protobuf.Timestamp mtime = 302;
+    google.protobuf.Timestamp ctime = 303;
+    google.protobuf.Timestamp atime = 304;
 
 }
 
 message MFFileChecksum {
     // 1.0 golang implementation must write a multihash here
     // it's ok to only ever use/verify sha256 multihash
-    bytes multiHash = 1;
+    required bytes multiHash = 1;
 }
 
 message MFFileInner {
@@ -57,13 +57,13 @@ message MFFileInner {
         NONE = 0;
         ONE = 1; // only one for now
     }
-    Version version = 101;
+    required Version version = 101;
 
     // required manifest attributes:
-    uint64 fileCount = 102; //FIXME is this necessary?
-    repeated MFFilePath files = 103;
+    required uint64 fileCount = 102; //FIXME is this necessary?
+    required repeated MFFilePath files = 103;
 
     // optional manifest attributes 2xx:
-    optional google.protobuf.Timestamp createdAt = 201;
+    google.protobuf.Timestamp createdAt = 201;
 }