diff --git a/enccnf b/enccnf
index 4e5c257..f6337aa 100755
--- a/enccnf
+++ b/enccnf
@@ -236,10 +236,10 @@ def parse_enc_file(enc_file, tftp_certificate_file):
 
     try:
         public_key.verify(signature, tlv_data, padding.PKCS1v15(), hashes.SHA512() if hash_algorithm == HASH_SHA512 else hashes.SHA1())
+
+        print('Valid signature')
     except InvalidSignature:
         print('Invalid signature')
-    else:
-        print('Valid signature')
 
 
 def remove_enc_file(enc_file, private_key_file):
@@ -459,34 +459,17 @@ def build_enc_file(cnf_file, tftp_certificate_file, certificate_file, hash_algor
     header_length_index = len(tlv_data)
     tlv_data += struct.pack('> B H H', HEADER_LENGTH, 2, 0)
 
-    signer_name = ''
-
-    for attribute in certificate.subject:
-        signer_name += (';' if len(signer_name) else '') + attribute.rfc4514_string()
-
-    signer_name = signer_name.encode('utf-8') + b'\x00'
-    issuer_name = ''
-
-    for attribute in certificate.issuer:
-        issuer_name += (';' if len(issuer_name) else '') + attribute.rfc4514_string()
-
-    issuer_name = issuer_name.encode('utf-8') + b'\x00'
+    signer_name = ','.join([attribute.rfc4514_string() for attribute in certificate.subject]).encode('utf-8') + b'\x00'
+    issuer_name = ','.join([attribute.rfc4514_string() for attribute in certificate.issuer]).encode('utf-8') + b'\x00'
 
     serial_number = certificate.serial_number
     serial_number = serial_number.to_bytes((serial_number.bit_length() + 7) // 8, byteorder = 'big')
 
-    signer_info = struct.pack('> B H', HEADER_SIGNER_NAME, len(signer_name))
-    signer_info += signer_name
-
-    signer_info += struct.pack('> B H', HEADER_SERIAL_NUMBER, len(serial_number))
-    signer_info += serial_number
-
-    signer_info += struct.pack('> B H', HEADER_ISSUER_NAME, len(issuer_name))
-    signer_info += issuer_name
-
-    tlv_data += struct.pack('> B H', HEADER_SIGNER_INFO, len(signer_info))
-    tlv_data += signer_info
+    signer_info = (struct.pack('> B H', HEADER_SIGNER_NAME, len(signer_name)) + signer_name +
+                   struct.pack('> B H', HEADER_ISSUER_NAME, len(issuer_name)) + issuer_name +
+                   struct.pack('> B H', HEADER_SERIAL_NUMBER, len(serial_number)) + serial_number)
 
+    tlv_data += struct.pack('> B H', HEADER_SIGNER_INFO, len(signer_info)) + signer_info
     tlv_data += struct.pack('> B H', HEADER_SIGNATURE_INFO, 15)
     tlv_data += struct.pack('> B H B', HEADER_HASH_ALGORITHM, 1, HASH_SHA512 if hash_algorithm == 'sha512' else HASH_SHA1)
 
@@ -499,9 +482,7 @@ def build_enc_file(cnf_file, tftp_certificate_file, certificate_file, hash_algor
 
     filename = os.path.basename(enc_file).encode('utf-8') + b'\x00'
 
-    tlv_data += struct.pack('> B H', HEADER_FILENAME, len(filename))
-    tlv_data += filename
-
+    tlv_data += struct.pack('> B H', HEADER_FILENAME, len(filename)) + filename
     tlv_data += struct.pack('> B H I', HEADER_TIMESTAMP, 4, int(time.time()))
 
     hash = hashes.Hash(hashes.SHA512() if hash_algorithm == 'sha512' else hashes.SHA1(), backends.default_backend())
@@ -522,33 +503,21 @@ def build_enc_file(cnf_file, tftp_certificate_file, certificate_file, hash_algor
     xml = encryptor.update(xml) + encryptor.finalize()
     encryption_key = device_public_key.encrypt(encryption_key, padding.PKCS1v15())
 
-    encryption_iv_info = struct.pack('> B H B', HEADER_ENCRYPTION_UNKNOWN1, 1, 0)
-
-    encryption_iv_info += struct.pack('> B H', HEADER_ENCRYPTION_IV, len(encryption_iv))
-    encryption_iv_info += encryption_iv
-
-    encryption_iv_info += struct.pack('> B H H', HEADER_ENCRYPTION_PADDING, 2, encryption_padding)
+    encryption_iv_info = (struct.pack('> B H B', HEADER_ENCRYPTION_UNKNOWN1, 1, 0) +
+                          struct.pack('> B H', HEADER_ENCRYPTION_IV, len(encryption_iv)) + encryption_iv +
+                          struct.pack('> B H H', HEADER_ENCRYPTION_PADDING, 2, encryption_padding))
 
-    encryption_key_info = struct.pack('> B H B', HEADER_ENCRYPTION_UNKNOWN2, 1, 0)
-    encryption_key_info += struct.pack('> B H H', HEADER_ENCRYPTION_KEY_SIZE, 2, len(encryption_key) * 8)
-    encryption_key_info += struct.pack('> B H B', HEADER_ENCRYPTION_KEY_ALGORITHM, 1, 1) # AES?
+    encryption_key_info = (struct.pack('> B H B', HEADER_ENCRYPTION_UNKNOWN2, 1, 0) +
+                           struct.pack('> B H H', HEADER_ENCRYPTION_KEY_SIZE, 2, len(encryption_key) * 8) +
+                           struct.pack('> B H B', HEADER_ENCRYPTION_KEY_ALGORITHM, 1, 1) + # AES?
+                           struct.pack('> B H', HEADER_ENCRYPTION_KEY, len(encryption_key)) + encryption_key)
 
-    encryption_key_info += struct.pack('> B H', HEADER_ENCRYPTION_KEY, len(encryption_key))
-    encryption_key_info += encryption_key
-
-    encryption_info = struct.pack('> B H', HEADER_ENCRYPTION_IV_INFO, len(encryption_iv_info))
-    encryption_info += encryption_iv_info
-
-    encryption_info += struct.pack('> B H', HEADER_ENCRYPTION_KEY_INFO, len(encryption_key_info))
-    encryption_info += encryption_key_info
-
-    tlv_data += struct.pack('> B H', HEADER_ENCRYPTION_INFO, len(encryption_info))
-    tlv_data += encryption_info
+    encryption_info = (struct.pack('> B H', HEADER_ENCRYPTION_IV_INFO, len(encryption_iv_info)) + encryption_iv_info +
+                       struct.pack('> B H', HEADER_ENCRYPTION_KEY_INFO, len(encryption_key_info)) + encryption_key_info)
 
+    tlv_data += struct.pack('> B H', HEADER_ENCRYPTION_INFO, len(encryption_info)) + encryption_info
     tlv_data += struct.pack('> B H B', HEADER_ENCRYPTION_HASH_ALGORITHM, 1, HASH_SHA512 if hash_algorithm == 'sha512' else HASH_SHA1)
-
-    tlv_data += struct.pack('> B H', HEADER_ENCRYPTION_HASH, len(encryption_hash))
-    tlv_data += encryption_hash
+    tlv_data += struct.pack('> B H', HEADER_ENCRYPTION_HASH, len(encryption_hash)) + encryption_hash
 
     # Pad to 4 byte boundary
     while (len(tlv_data) + 3 + signature_length) % 4:
@@ -565,8 +534,7 @@ def build_enc_file(cnf_file, tftp_certificate_file, certificate_file, hash_algor
     try:
         with open(enc_file, 'wb') as file:
             file.write(tlv_data[:signature_index])
-            file.write(struct.pack('> B H', HEADER_SIGNATURE, len(signature)))
-            file.write(signature)
+            file.write(struct.pack('> B H', HEADER_SIGNATURE, len(signature)) + signature)
             file.write(tlv_data[signature_index:])
 
     except (PermissionError, IsADirectoryError) as error:
@@ -601,34 +569,17 @@ def build_enc_file(cnf_file, tftp_certificate_file, certificate_file, hash_algor
     header_length_index = len(tlv_data)
     tlv_data += struct.pack('> B H H', HEADER_LENGTH, 2, 0)
 
-    signer_name = ''
-
-    for attribute in certificate.subject:
-        signer_name += (';' if len(signer_name) else '') + attribute.rfc4514_string()
-
-    signer_name = signer_name.encode('utf-8') + b'\x00'
-    issuer_name = ''
-
-    for attribute in certificate.issuer:
-        issuer_name += (';' if len(issuer_name) else '') + attribute.rfc4514_string()
-
-    issuer_name = issuer_name.encode('utf-8') + b'\x00'
+    signer_name = ','.join([attribute.rfc4514_string() for attribute in certificate.subject]).encode('utf-8') + b'\x00'
+    issuer_name = ','.join([attribute.rfc4514_string() for attribute in certificate.issuer]).encode('utf-8') + b'\x00'
 
     serial_number = certificate.serial_number
     serial_number = serial_number.to_bytes((serial_number.bit_length() + 7) // 8, byteorder = 'big')
 
-    signer_info = struct.pack('> B H', HEADER_SIGNER_NAME, len(signer_name))
-    signer_info += signer_name
-
-    signer_info += struct.pack('> B H', HEADER_SERIAL_NUMBER, len(serial_number))
-    signer_info += serial_number
-
-    signer_info += struct.pack('> B H', HEADER_ISSUER_NAME, len(issuer_name))
-    signer_info += issuer_name
-
-    tlv_data += struct.pack('> B H', HEADER_SIGNER_INFO, len(signer_info))
-    tlv_data += signer_info
+    signer_info = (struct.pack('> B H', HEADER_SIGNER_NAME, len(signer_name)) + signer_name +
+                   struct.pack('> B H', HEADER_ISSUER_NAME, len(issuer_name)) + issuer_name +
+                   struct.pack('> B H', HEADER_SERIAL_NUMBER, len(serial_number)) + serial_number)
 
+    tlv_data += struct.pack('> B H', HEADER_SIGNER_INFO, len(signer_info)) + signer_info
     tlv_data += struct.pack('> B H', HEADER_SIGNATURE_INFO, 15)
     tlv_data += struct.pack('> B H B', HEADER_HASH_ALGORITHM, 1, HASH_SHA512 if hash_algorithm == 'sha512' else HASH_SHA1)
 
@@ -641,9 +592,7 @@ def build_enc_file(cnf_file, tftp_certificate_file, certificate_file, hash_algor
 
     filename = os.path.basename(sgn_file).encode('utf-8') + b'\x00'
 
-    tlv_data += struct.pack('> B H', HEADER_FILENAME, len(filename))
-    tlv_data += filename
-
+    tlv_data += struct.pack('> B H', HEADER_FILENAME, len(filename)) + filename
     tlv_data += struct.pack('> B H I', HEADER_TIMESTAMP, 4, int(time.time()))
 
     # Pad to 4 byte boundary
@@ -661,8 +610,7 @@ def build_enc_file(cnf_file, tftp_certificate_file, certificate_file, hash_algor
     try:
         with open(sgn_file, 'wb') as file:
             file.write(tlv_data[:signature_index])
-            file.write(struct.pack('> B H', HEADER_SIGNATURE, len(signature)))
-            file.write(signature)
+            file.write(struct.pack('> B H', HEADER_SIGNATURE, len(signature)) + signature)
             file.write(tlv_data[signature_index:])
 
     except (PermissionError, IsADirectoryError) as error:
diff --git a/mkcert b/mkcert
index be928ed..c40c54a 100755
--- a/mkcert
+++ b/mkcert
@@ -106,7 +106,7 @@ while [[ -n $1 ]]; do
         shift 1
         ;;
     -H|--help)
-        echo "Usage: ${0##*/} [OPTIONS] [PEM-FILE]"
+        echo "Usage: ${0##*/} [OPTIONS] [FILE]"
         echo "Create a self-signed X509 certificate."
         echo ""
         echo "  -c, --common COMMON-NAME           common name, required"
@@ -117,9 +117,9 @@ while [[ -n $1 ]]; do
         echo "  -C, --country COUNTRY              country code"
         echo "  -y, --years NUMBER                 number of years to sign the certificate (default 10)"
         echo "  -b, --bits, --key-size BITS        RSA key-size (default 2048)"
-        echo "  -E, --curve CURVE                  EC algorithm"
+        echo "  -E, --curve CURVE                  EC name (secp256r1, secpr384r1 or secp512r1)"
         echo "  -d, --digest DIGEST                message digest to use: sha1, sha256 or sha512 (default sha256)"
-        echo "  -f, --file PEM-FILE                output file (default COMMON-NAME.pem)"
+        echo "  -f, --file FILE                    output file (default COMMON-NAME.pem)"
         echo "  -h, --help                         print this help and exit"
         echo ""
 
diff --git a/sgnfile b/sgnfile
index b37d8ce..6d0d8b9 100755
--- a/sgnfile
+++ b/sgnfile
@@ -188,10 +188,10 @@ def parse_sgn_file(sgn_file, tftp_certificate_file):
 
     try:
         public_key.verify(signature, tlv_data, padding.PKCS1v15(), hashes.SHA512() if hash_algorithm == HASH_SHA512 else hashes.SHA1())
+
+        print('Valid signature')
     except InvalidSignature:
         print('Invalid signature')
-    else:
-        print('Valid signature')
 
 
 def remove_sgn_file(sgn_file):
@@ -210,7 +210,6 @@ def remove_sgn_file(sgn_file):
     if tlv_tag != HEADER_VERSION:
         raise ProgramError(f'Tag is not header version: {tlv_tag}')
 
-    # Skip version
     tlv_index += tlv_length
 
     (tlv_tag, tlv_length) = struct.unpack_from('> B H', tlv_data, tlv_index)
@@ -278,34 +277,17 @@ def build_sgn_file(input_file, tftp_certificate_file, hash_algorithm, filename):
     header_length_index = len(tlv_data)
     tlv_data += struct.pack('> B H H', HEADER_LENGTH, 2, 0)
 
-    signer_name = ''
-
-    for attribute in certificate.subject:
-        signer_name += (';' if len(signer_name) else '') + attribute.rfc4514_string()
-
-    signer_name = signer_name.encode('utf-8') + b'\x00'
-    issuer_name = ''
-
-    for attribute in certificate.issuer:
-        issuer_name += (';' if len(issuer_name) else '') + attribute.rfc4514_string()
-
-    issuer_name = issuer_name.encode('utf-8') + b'\x00'
+    signer_name = ','.join([attribute.rfc4514_string() for attribute in certificate.subject]).encode('utf-8') + b'\x00'
+    issuer_name = ','.join([attribute.rfc4514_string() for attribute in certificate.issuer]).encode('utf-8') + b'\x00'
 
     serial_number = certificate.serial_number
     serial_number = serial_number.to_bytes((serial_number.bit_length() + 7) // 8, byteorder = 'big')
 
-    signer_info = struct.pack('> B H', HEADER_SIGNER_NAME, len(signer_name))
-    signer_info += signer_name
-
-    signer_info += struct.pack('> B H', HEADER_SERIAL_NUMBER, len(serial_number))
-    signer_info += serial_number
-
-    signer_info += struct.pack('> B H', HEADER_ISSUER_NAME, len(issuer_name))
-    signer_info += issuer_name
-
-    tlv_data += struct.pack('> B H', HEADER_SIGNER_INFO, len(signer_info))
-    tlv_data += signer_info
+    signer_info = (struct.pack('> B H', HEADER_SIGNER_NAME, len(signer_name)) + signer_name +
+                   struct.pack('> B H', HEADER_ISSUER_NAME, len(issuer_name)) + issuer_name +
+                   struct.pack('> B H', HEADER_SERIAL_NUMBER, len(serial_number)) + serial_number)
 
+    tlv_data += struct.pack('> B H', HEADER_SIGNER_INFO, len(signer_info)) + signer_info
     tlv_data += struct.pack('> B H', HEADER_SIGNATURE_INFO, 15)
     tlv_data += struct.pack('> B H B', HEADER_HASH_ALGORITHM, 1, HASH_SHA512 if hash_algorithm == 'sha512' else HASH_SHA1)
 
@@ -315,12 +297,9 @@ def build_sgn_file(input_file, tftp_certificate_file, hash_algorithm, filename):
 
     # Index where the signature will be inserted
     signature_index = len(tlv_data)
-
     filename = filename.encode('utf-8') + b'\x00'
 
-    tlv_data += struct.pack('> B H', HEADER_FILENAME, len(filename))
-    tlv_data += filename
-
+    tlv_data += struct.pack('> B H', HEADER_FILENAME, len(filename)) + filename
     tlv_data += struct.pack('> B H I', HEADER_TIMESTAMP, 4, int(time.time()))
 
     # Pad to 4 byte boundary
@@ -338,8 +317,7 @@ def build_sgn_file(input_file, tftp_certificate_file, hash_algorithm, filename):
     try:
         with open(sgn_file, 'wb') as file:
             file.write(tlv_data[:signature_index])
-            file.write(struct.pack('> B H', HEADER_SIGNATURE, len(signature)))
-            file.write(signature)
+            file.write(struct.pack('> B H', HEADER_SIGNATURE, len(signature)) + signature)
             file.write(tlv_data[signature_index:])
 
     except (PermissionError, IsADirectoryError) as error:
diff --git a/tlvfile b/tlvfile
index 32c41db..a290c5d 100755
--- a/tlvfile
+++ b/tlvfile
@@ -330,10 +330,10 @@ def parse_tlv_file(tlv_file):
 
     try:
         public_key.verify(signature, tlv_data, padding.PKCS1v15(), hashes.SHA512() if hash_algorithm == HASH_SHA512 else hashes.SHA1())
+
+        print('Valid signature')
     except InvalidSignature:
         print('Invalid signature')
-    else:
-        print('Valid signature')
 
 
 def build_tlv_file(tlv_file, sast_certificate_file, version, hash_algorithm, filename, certificate_records):
@@ -373,34 +373,17 @@ def build_tlv_file(tlv_file, sast_certificate_file, version, hash_algorithm, fil
     (major, minor) = version.split('.')
     tlv_data += struct.pack('> B H B B', HEADER_SIGNER_VERSION, 2, int(major), int(minor))
 
-    signer_name = ''
-
-    for attribute in certificate.subject:
-        signer_name += (';' if len(signer_name) else '') + attribute.rfc4514_string()
-
-    signer_name = signer_name.encode('utf-8') + b'\x00'
-    issuer_name = ''
-
-    for attribute in certificate.issuer:
-        issuer_name += (';' if len(issuer_name) else '') + attribute.rfc4514_string()
-
-    issuer_name = issuer_name.encode('utf-8') + b'\x00'
+    signer_name = ','.join([attribute.rfc4514_string() for attribute in certificate.subject]).encode('utf-8') + b'\x00'
+    issuer_name = ','.join([attribute.rfc4514_string() for attribute in certificate.issuer]).encode('utf-8') + b'\x00'
 
     serial_number = certificate.serial_number
     serial_number = serial_number.to_bytes((serial_number.bit_length() + 7) // 8, byteorder = 'big')
 
-    signer_info = struct.pack('> B H', HEADER_SIGNER_NAME, len(signer_name))
-    signer_info += signer_name
-
-    signer_info += struct.pack('> B H', HEADER_SERIAL_NUMBER, len(serial_number))
-    signer_info += serial_number
-
-    signer_info += struct.pack('> B H', HEADER_ISSUER_NAME, len(issuer_name))
-    signer_info += issuer_name
-
-    tlv_data += struct.pack('> B H', HEADER_SIGNER_INFO, len(signer_info))
-    tlv_data += signer_info
+    signer_info = (struct.pack('> B H', HEADER_SIGNER_NAME, len(signer_name)) + signer_name +
+                   struct.pack('> B H', HEADER_ISSUER_NAME, len(issuer_name)) + issuer_name +
+                   struct.pack('> B H', HEADER_SERIAL_NUMBER, len(serial_number)) + serial_number)
 
+    tlv_data += struct.pack('> B H', HEADER_SIGNER_INFO, len(signer_info)) + signer_info
     tlv_data += struct.pack('> B H', HEADER_SIGNATURE_INFO, 15)
     tlv_data += struct.pack('> B H B', HEADER_HASH_ALGORITHM, 1, HASH_SHA512 if hash_algorithm == 'sha512' else HASH_SHA1)
 
@@ -410,12 +393,9 @@ def build_tlv_file(tlv_file, sast_certificate_file, version, hash_algorithm, fil
 
     # Index where the signature will be inserted
     signature_index = len(tlv_data)
-
     filename = filename.encode('utf-8') + b'\x00'
 
-    tlv_data += struct.pack('> B H', HEADER_FILENAME, len(filename))
-    tlv_data += filename
-
+    tlv_data += struct.pack('> B H', HEADER_FILENAME, len(filename)) + filename
     tlv_data += struct.pack('> B H I', HEADER_TIMESTAMP, 4, int(time.time()))
 
     # Pad to 4 byte boundary
@@ -446,15 +426,15 @@ def build_tlv_file(tlv_file, sast_certificate_file, version, hash_algorithm, fil
         record_length_index = len(tlv_data)
         tlv_data += struct.pack('> B H H', RECORD_LENGTH, 2, 0)
 
-        subject_name = ''
-
-        for attribute in certificate.subject:
-            subject_name += (';' if len(subject_name) else '') + attribute.rfc4514_string()
+        subject_name = ','.join([attribute.rfc4514_string() for attribute in certificate.subject]).encode('utf-8') + b'\x00'
+        issuer_name = ','.join([attribute.rfc4514_string() for attribute in certificate.issuer]).encode('utf-8') + b'\x00'
 
-        subject_name = subject_name.encode('utf-8') + b'\x00'
+        serial_number = certificate.serial_number
+        serial_number = serial_number.to_bytes((serial_number.bit_length() + 7) // 8, byteorder = 'big')
 
-        tlv_data += struct.pack('> B H', RECORD_SUBJECT_NAME, len(subject_name))
-        tlv_data += subject_name
+        tlv_data += struct.pack('> B H', RECORD_SUBJECT_NAME, len(subject_name)) + subject_name
+        tlv_data += struct.pack('> B H', RECORD_ISSUER_NAME, len(issuer_name)) + issuer_name
+        tlv_data += struct.pack('> B H', RECORD_SERIAL_NUMBER, len(serial_number)) + serial_number
 
         tlv_data += struct.pack('> B H', RECORD_ROLE, 2)
 
@@ -475,20 +455,6 @@ def build_tlv_file(tlv_file, sast_certificate_file, version, hash_algorithm, fil
         else:
             raise ProgramError(f'Unsupported record role: {role}')
 
-        issuer_name = ''
-
-        for attribute in certificate.issuer:
-            issuer_name += (';' if len(issuer_name) else '') + attribute.rfc4514_string()
-
-        issuer_name = issuer_name.encode('utf-8') + b'\x00'
-        tlv_data += struct.pack('> B H', RECORD_ISSUER_NAME, len(issuer_name)) + issuer_name
-
-        serial_number = certificate.serial_number
-        serial_number = serial_number.to_bytes((serial_number.bit_length() + 7) // 8, byteorder = 'big')
-
-        tlv_data += struct.pack('> B H', RECORD_SERIAL_NUMBER, len(serial_number))
-        tlv_data += serial_number
-
         if isinstance(public_key, rsa.RSAPublicKey):
             public_key = public_key.public_bytes(serialization.Encoding.DER, serialization.PublicFormat.PKCS1)
         elif isinstance(public_key, ec.EllipticCurvePublicKey):
@@ -496,18 +462,13 @@ def build_tlv_file(tlv_file, sast_certificate_file, version, hash_algorithm, fil
         else:
             raise ProgramError('Unsupported certificate public-key type')
 
-        tlv_data += struct.pack('> B H', RECORD_PUBLIC_KEY, len(public_key))
-        tlv_data += public_key
+        tlv_data += struct.pack('> B H', RECORD_PUBLIC_KEY, len(public_key)) + public_key
 
         signature = certificate.signature
-
-        tlv_data += struct.pack('> B H', RECORD_SIGNATURE, len(signature))
-        tlv_data += signature
-
         certificate = certificate.public_bytes(serialization.Encoding.DER)
 
-        tlv_data += struct.pack('> B H', RECORD_CERTIFICATE, len(certificate))
-        tlv_data += certificate
+        tlv_data += struct.pack('> B H', RECORD_SIGNATURE, len(signature)) + signature
+        tlv_data += struct.pack('> B H', RECORD_CERTIFICATE, len(certificate)) + certificate
 
         record_length = len(tlv_data) - record_length_index
         struct.pack_into('> H', tlv_data, record_length_index + 3, record_length)
@@ -518,8 +479,7 @@ def build_tlv_file(tlv_file, sast_certificate_file, version, hash_algorithm, fil
     try:
         with open(tlv_file, 'wb') as file:
             file.write(tlv_data[:signature_index])
-            file.write(struct.pack('> B H', HEADER_SIGNATURE, len(signature)))
-            file.write(signature)
+            file.write(struct.pack('> B H', HEADER_SIGNATURE, len(signature)) + signature)
             file.write(tlv_data[signature_index:])
 
     except (PermissionError, IsADirectoryError) as error: