diff --git a/protobuf/bitkey.proto b/protobuf/bitkey.proto
index 8364a4f..9e18b6b 100644
--- a/protobuf/bitkey.proto
+++ b/protobuf/bitkey.proto
@@ -31,16 +31,16 @@ message Initialize {
 
 // Response object for Initialize. Contains list of available features on the device.
 message Features {
-    required bytes session_id = 1;	// Echoed back from Initialize message
+    optional bytes session_id = 1;	// Echoed back from Initialize message
     optional string vendor = 2;	// Name of the manufacturer, e.g. "bitkey" 
     optional uint32 major_version = 3; // Major version of the device, e.g. 1
     optional uint32 minor_version = 4;  // Minor version of the device, e.g. 0
-    optional bool otp = 5;	// True when device will send OtpRequest on important action
-    optional bool pin = 6;	// True when device will send PinRequest on important action
-    optional bool spv = 7;	// True when device requires SPV verification of transaction inputs
-    optional uint64 maxfee_kb = 8;	// Maximum accepted fee per kilobyte of signed transaction 
-    repeated Algorithm algo = 9;	// List of key generation algorithms supported by the device
-    optional bool debug_link = 10;	// Indicates support for DebugLink connection  
+    optional bool has_otp = 5;	// True when device will send OtpRequest on important action
+    optional bool has_spv = 6;	// True when device requires SPV verification of transaction inputs
+    optional bool pin = 7;	// True when device will send PinRequest on important action
+    optional Algorithm algo = 8; // Choosen generation algorithm
+    repeated Algorithm algo_available = 9;	// List of key generation algorithms supported by the device
+    optional uint64 maxfee_kb = 10;	// Maximum accepted fee per kilobyte of signed transaction
 }
 
 // Test if device is live, device will send back the message on success
@@ -180,7 +180,6 @@ message SetMaxFeeKb {
 //
 // Response: MasterPublicKey, Failure
 message GetMasterPublicKey {
-    required Algorithm algo = 1 [default=BIP32]; // Used algorithm for generating the master public key
 }
 
 // Contains master public key derived from device's seed.
@@ -189,12 +188,11 @@ message MasterPublicKey {
 }
 
 message GetAddress {
-    required Algorithm algo = 1 [default=BIP32]; // Used algorithm for generating the address
-    repeated uint32 address_n = 2;	// Parameter for address generation algorithm to derive the address from the master public key 
+    repeated uint32 address_n = 1;	// Parameter for address generation algorithm to derive the address from the master public key 
 }
 
 message Address {
-    required string address = 1; // Bitcoin address in base58 encoding corresponding to GetAddress(algo, n) call
+    required string address = 1; // Bitcoin address in base58 encoding corresponding to GetAddress(n) call
 }
 
 // Load seed and related internal settings from computer to the device. Existing seed is overwritten.
@@ -220,7 +218,6 @@ message ResetDevice {
 //
 // Response: TxRequest, OtpRequest, PinRequest, Failure
 message SignTx {
-    required Algorithm algo = 1 [default=BIP32];	// Algorithm using for key generation algorithm
     required uint32 outputs_count = 3;		// Count of outputs of the transaction 
     required uint32 inputs_count = 5; // Count of inputs of the transaction
     optional bytes random = 6; 	// Provide additional entropy for signing function.
@@ -234,7 +231,7 @@ message SignTx {
 message TxRequest {
 	optional int32 request_index = 1;	// If >=0, device expects TxInput/TxOutput message from the computer
 	optional RequestType request_type = 2; // Ask for TxInput or TxOutput?
-	optional int32 signed_index = 3 [default=-1]; // If >=0, 'signature' contains signed input of this input
+	optional int32 signed_index = 3;	// If >=0, 'signature' contains signed input of this input
 	optional bytes signature = 4;		// If signed_index>=0, represent signature of the signed_index input
 	optional bytes serialized_tx = 5;   // Part of serialized and signed transaction
 }