S-57 vector charts may be encrypted following the S-63 standard. Decryption is done by means of a "user permit".
The user permit, containing a Manufacturer identifier (client id), is submitted to the chart vendor who will provide the encrypted charts.
On this page:
S-63 Encrypted Charts
Charts that were uploaded to the Apple device are encrypted and require a user permit which can be entered in the Qastor 3 Settings.
Multiple permits may be entered, provided they are separated by a comma or semicolon.
Select: Settings - Chart Preferences - User permit (scroll down on the Chart Preferences page)
A user permit contains 28 (hexadecimal) characters.
It can be found in the "User Permit.txt" file as generated by ENC Administrator.