diff --git a/legacy/firmware/ethereum_definitions.c b/legacy/firmware/ethereum_definitions.c
index ac96515cc..372bb561e 100644
--- a/legacy/firmware/ethereum_definitions.c
+++ b/legacy/firmware/ethereum_definitions.c
@@ -37,6 +37,29 @@
 
 typedef pb_byte_t proof_entry[SHA256_DIGEST_LENGTH];
 
+#define SIGNATURE_THRESHOLD 2
+#define DEFS_PUBLIC_KEYS_COUNT 3
+
+const ed25519_public_key DEFS_PUBLIC_KEYS[DEFS_PUBLIC_KEYS_COUNT] = {
+    "\x43\x34\x99\x63\x43\x62\x3e\x46\x2f\x0f\xc9\x33\x11\xfe\xf1\x48\x4c\xa2"
+    "\x3d\x2f\xf1\xee\xc6\xdf\x1f\xa8\xeb\x7e\x35\x73\xb3\xdb",
+    "\xa9\xa2\x2c\xc2\x65\xa0\xcb\x1d\x6c\xb3\x29\xbc\x0e\x60\xbc\x45\xdf\x76"
+    "\xb9\xab\x28\xfb\x87\xb6\x11\x36\xfe\xaf\x8d\x8f\xdc\x96",
+    "\xb8\xd2\xb2\x1d\xe2\x71\x24\xf0\x51\x1f\x90\x3a\xe7\xe6\x0e\x07\x96\x18"
+    "\x10\xa0\xb8\xf2\x8e\xa7\x55\xfa\x50\x36\x7a\x8a\x2b\x8b",
+};
+
+#if DEBUG_LINK
+const ed25519_public_key DEFS_PUBLIC_KEYS_DEV[DEFS_PUBLIC_KEYS_COUNT] = {
+    "\x68\x46\x0e\xbe\xf3\xb1\x38\x16\x4e\xc7\xfd\x86\x10\xe9\x58\x00\xdf"
+    "\x75\x98\xf7\x0f\x2f\x2e\xa7\xdb\x51\x72\xac\x74\xeb\xc1\x44",
+    "\x8d\x4a\xbe\x07\x4f\xef\x92\x29\xd3\xb4\x41\xdf\xea\x4f\x98\xf8\x05"
+    "\xb1\xa2\xb3\xa0\x6a\xe6\x45\x81\x0e\xfe\xce\x77\xfd\x50\x44",
+    "\x97\xf7\x13\x5a\x9a\x26\x90\xe7\x3b\xeb\x26\x55\x6f\x1c\xb1\x63\xbe"
+    "\xa2\x53\x2a\xff\xa1\xe7\x78\x24\x30\xbe\x98\xc0\xe5\x68\x12",
+};
+#endif
+
 struct EncodedDefinition {
   // prefix
   pb_byte_t format_version[FORMAT_VERSION_LENGTH];
@@ -51,16 +74,17 @@ struct EncodedDefinition {
   uint8_t proof_length;
   const proof_entry *proof;
 
-  const ed25519_signature *signed_root_hash;
+  uint8_t sigmask;
+  const uint8_t *signature;
 };
 
 static bool parse_encoded_definition(struct EncodedDefinition *const result,
                                      const pb_size_t size,
                                      const pb_byte_t *bytes) {
   // format version + definition type + data version + payload length + payload
-  // (at least 1B) + proof length + signed Merkle tree root hash
-  if (size < (FORMAT_VERSION_LENGTH + 1 + 4 + 2 + 1 + 1 +
-              MERKLE_TREE_SIGNED_ROOT_SIZE)) {
+  // (at least 1B) + proof length + sigmask + signature
+  if (size < (FORMAT_VERSION_LENGTH + 1 + 4 + 2 + 1 + 1 + 1 +
+              sizeof(ed25519_signature))) {
     return false;
   }
 
@@ -88,13 +112,15 @@ static bool parse_encoded_definition(struct EncodedDefinition *const result,
 
   // check the whole size of incoming bytes array
   if (size != (cursor - bytes) + result->proof_length * sizeof(proof_entry) +
-                  MERKLE_TREE_SIGNED_ROOT_SIZE) {
+                  1 + sizeof(ed25519_signature)) {
     return false;
   }
   result->proof = (proof_entry *)cursor;
   cursor += result->proof_length * sizeof(proof_entry);
 
-  result->signed_root_hash = (ed25519_signature *)cursor;
+  result->sigmask = *cursor;
+  cursor += 1;
+  result->signature = cursor;
 
   return true;
 }
@@ -160,12 +186,13 @@ static bool decode_definition(const pb_size_t size, const pb_byte_t *bytes,
   }
 
   // and verify its signature
-  if (ed25519_sign_open(hash, SHA256_DIGEST_LENGTH, DEFINITIONS_PUBLIC_KEY,
-                        *(parsed_def.signed_root_hash)) != 0
+  if (!cryptoCosiVerify(parsed_def.signature, hash, sizeof(hash),
+                        SIGNATURE_THRESHOLD, DEFS_PUBLIC_KEYS,
+                        DEFS_PUBLIC_KEYS_COUNT, parsed_def.sigmask)
 #if DEBUG_LINK
-      &&
-      ed25519_sign_open(hash, SHA256_DIGEST_LENGTH, DEFINITIONS_DEV_PUBLIC_KEY,
-                        *(parsed_def.signed_root_hash)) != 0
+      && !cryptoCosiVerify(parsed_def.signature, hash, sizeof(hash),
+                           SIGNATURE_THRESHOLD, DEFS_PUBLIC_KEYS_DEV,
+                           DEFS_PUBLIC_KEYS_COUNT, parsed_def.sigmask)
 #endif
   ) {
     // invalid signature
diff --git a/legacy/firmware/ethereum_definitions_constants.h.mako b/legacy/firmware/ethereum_definitions_constants.h.mako
index 1a2a28c65..ea4dd8251 100644
--- a/legacy/firmware/ethereum_definitions_constants.h.mako
+++ b/legacy/firmware/ethereum_definitions_constants.h.mako
@@ -10,17 +10,8 @@
 #include "messages-ethereum-definitions.pb.h"
 #include "pb.h"
 
-static const uint8_t DEFINITIONS_PUBLIC_KEY[] =
-    "                                "; // TODO: update
-#if DEBUG_LINK
-static const uint8_t DEFINITIONS_DEV_PUBLIC_KEY[] =
-    "\xdb\x99\x5f\xe2\x51\x69\xd1\x41\xca\xb9\xbb\xba\x92\xba\xa0\x1f\x9f\x2e"
-    "\x1e\xce\x7d\xf4\xcb\x2a\xc0\x51\x90\xf3\x7f\xcc\x1f\x9d";
-#endif
-
 #define MIN_DATA_VERSION ${ethereum_defs_timestamp}
 #define FORMAT_VERSION_LENGTH 5
 #define FORMAT_VERSION (const pb_byte_t *)"trzd1"
-#define MERKLE_TREE_SIGNED_ROOT_SIZE sizeof(ed25519_signature)
 
 #endif