diff --git a/doc/usage.md b/doc/usage.md
index 80c7d1e..6dd2eb9 100644
--- a/doc/usage.md
+++ b/doc/usage.md
@@ -30,7 +30,7 @@ PIN=648219
 ## Initialization
 The first step is to initialize the HSM. To do so, use the `pico-hsm-tool.py` in `tools` folder:
 ```
-$ python3 pico-hsm-tool initialize --so-pin 3537363231383830 --pin 648219
+$ python3 pico-hsm-tool.py initialize --so-pin 3537363231383830 --pin 648219
 ```
 The PIN number is used to manage all private keys in the device. It supports three attemps. After the third PIN failure, it gets blocked.
 The PIN accepts from 6 to 16 characters.
diff --git a/tools/pico-hsm-tool.py b/tools/pico-hsm-tool.py
old mode 100755
new mode 100644
index 41df2b7..00b399c
--- a/tools/pico-hsm-tool.py
+++ b/tools/pico-hsm-tool.py
@@ -24,17 +24,16 @@ try:
     from smartcard.CardType import AnyCardType
     from smartcard.CardRequest import CardRequest
     from smartcard.Exceptions import CardRequestTimeoutException
-except:
+except ModuleNotFoundError:
     print('ERROR: smarctard module not found! Install pyscard package.\nTry with `pip install pyscard`')
     sys.exit(-1)
 
 try:
+    from cvc.certificates import CVC
     from cvc.asn1 import ASN1
     from cvc.oid import oid2scheme
     from cvc.utils import scheme_rsa
-    from cvc.certificates import CVC
-
-except:
+except ModuleNotFoundError:
     print('ERROR: cvc module not found! Install pycvc package.\nTry with `pip install pycvc`')
     sys.exit(-1)
 
@@ -44,7 +43,7 @@ try:
     from cryptography.hazmat.primitives.serialization import Encoding, PublicFormat
     from cryptography.hazmat.primitives.ciphers.aead import ChaCha20Poly1305
     from cryptography.hazmat.primitives import hashes
-except:
+except ModuleNotFoundError:
     print('ERROR: cryptography module not found! Install cryptography package.\nTry with `pip install cryptography`')
     sys.exit(-1)