diff --git a/sign/hdr.pb.go b/sign/hdr.pb.go
index eb45149..b1c4cb7 100644
--- a/sign/hdr.pb.go
+++ b/sign/hdr.pb.go
@@ -25,6 +25,11 @@ var _ = math.Inf
 // proto package needs to be updated.
 const _ = proto.GoGoProtoPackageIsVersion3 // please upgrade the proto package
 
+//
+// Every encrypted file starts with a header describing the
+// Block Size, Salt, Recipient keys etc. Header represents a
+// decoded version of this information. It is encoded in
+// protobuf format before writing to disk.
 type Header struct {
 	ChunkSize uint32        `protobuf:"varint,1,opt,name=chunk_size,json=chunkSize,proto3" json:"chunk_size,omitempty"`
 	Salt      []byte        `protobuf:"bytes,2,opt,name=salt,proto3" json:"salt,omitempty"`
@@ -84,6 +89,9 @@ func (m *Header) GetKeys() []*WrappedKey {
 	return nil
 }
 
+//
+// A file encryption key is wrapped by a recipient specific public
+// key. WrappedKey describes such a wrapped key.
 type WrappedKey struct {
 	PkHash []byte `protobuf:"bytes,1,opt,name=pk_hash,json=pkHash,proto3" json:"pk_hash,omitempty"`
 	Pk     []byte `protobuf:"bytes,2,opt,name=pk,proto3" json:"pk,omitempty"`
diff --git a/sign/hdr.proto b/sign/hdr.proto
index 509312a..7b7f80b 100644
--- a/sign/hdr.proto
+++ b/sign/hdr.proto
@@ -9,12 +9,22 @@ package sign;
 //option (gogoproto.unmarshaler_all) = true;
 //option (gogoproto.goproto_getters_all) = false;
 
+/*
+ * Every encrypted file starts with a header describing the
+ * Block Size, Salt, Recipient keys etc. Header represents a
+ * decoded version of this information. It is encoded in
+ * protobuf format before writing to disk.
+ */
 message header {
 	uint32 chunk_size = 1;
 	bytes  salt = 2;
 	repeated wrapped_key keys = 3;
 }
 
+/*
+ * A file encryption key is wrapped by a recipient specific public
+ * key. WrappedKey describes such a wrapped key.
+ */
 message wrapped_key {
 	bytes pk_hash = 1; // hash of Ed25519 PK
 	bytes pk = 2;	    // curve25519 PK
diff --git a/version b/version
index ac39a10..f374f66 100644
--- a/version
+++ b/version
@@ -1 +1 @@
-0.9.0
+0.9.1