1. Problem phenomenon

The workbench that is normally used on weekdays finds that it cannot connect to the corresponding database after restarting the computer, and the workbench log displays

SSH tunnel]: Authentication error opening SSH tunnel: Authentication error, unhandled exception caught in tunnel manager, please refer to logs for details

Check the complete log and find the following:

$ tail -f ~/.mysql/workbench/log/wb.log 
  File "/usr/share/mysql-workbench/sshtunnel.py", line 303, in _connect_ssh
    look_for_keys=has_key, allow_agent=has_key, timeout=SSH_CONNECTION_TIMEOUT)
  File "/usr/lib/python2.7/dist-packages/paramiko/client.py", line 325, in connect
    t.start_client()
  File "/usr/lib/python2.7/dist-packages/paramiko/transport.py", line 492, in start_client
    raise e
NotImplementedError: Use module Crypto.Signature.pkcs1_15 instead

14:17:14 [INF][     SSH tunnel]: TunnelManager.wait_connection authentication error: Authentication error, unhandled exception caught in tunnel manager, please refer to logs for details
14:17:14 [ERR][     SSH tunnel]: Authentication error opening SSH tunnel: Authentication error, unhandled exception caught in tunnel manager, please refer to logs for details
14:18:24 [INF][      WBContext]: Connection to XinJangCityWolMart cancelled by user: Tunnel connection cancelled

The point is

NotImplementedError: Use module Crypto.Signature.pkcs1_15 instead

Found after querying with PIP list

$ pip2 list | grep crypto
asn1crypto (1.4.0)
cryptography (2.7)
pycrypto (2.6.1)
pycryptodome (3.11.0)

There is a pycryptodome , which may be installed when installing other tools later
​

2. Solutions

Uninstall pycryptodome

sudo pip2 uninstall pycryptodome

Then reopen the workbench to connect to the database and return to normal.