Unable to start migration in Plesk: q must be exactly 160, 224, or 256 bits long

Vincent Lauton

Updated January 13, 2026 19:12

kb: technical ext: migrator

Symptoms

Migration using SSH key cannot be initialized with the error in Plesk > Tools & Settings > Migration and Transfer Manager:

CONFIG_TEXT: Failed to check SSH connection to the source server 'source' (203.0.113.2): q must be exactly 160, 224, or 256 bits long

SSH keys required for the migration are not installed properly.

Apply one of two possible solutions:

To re-generate SSH keys:

Connect to the target server via SSH.
Re-configure SSH keys as per the guide: Migration Guide: Authentication by SSH (Linux) .
Re-start the migration using the SSH keys authorization.

If the issue still persists, check that the files below have the same permissions on the target and on the source server:

# stat ~/ | grep Access | head -n1

# stat ~/.ssh | grep Access | head -n1 \

# stat ~/.ssh/authorized_keys | grep Access | head -n1

Change the authorization method from SSH keys to User / password for migration.

To change the authorization method from 'SSH keys' to 'User / password':

Log into Plesk.
Go to Tools & Settings > Migration and Transfer manager.
Finish the current migration session by clicking on the Finish Migration.
Confirm clearing all settings.
Press the Start a New Migration button to start a new migration session.
Set Authorization as User / password and specify root user's password.
Adjust other settings.
Press the Prepare migration button to start a new migration session.

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