When setting up passwords for login accounts on the router, if you assigned plain-text passwords, the default encryption is SHA1. You want to change this to either DES or MD5.
Use the following command to change the encryption used for plain-text passwords to DES:
 aviva@router1# set system login password format des
For MD5 encryption, use the following command:
 aviva@router1# set system login password format md5
All passwords that you enter in a JUNOS configuration are encrypted. For plain-text passwords, you can use one of three types of encryption: SHA1 (the default and the strongest), MD5, or DES. The encryption type that you configure is used for all plain-text passwords. You cannot specify different encryption types for different users.
Router Configuration and File Management
Basic Router Security and Access Control
Routing Policy and Firewall Filters