You can easily encrypt the ISO into a zip or RAR file, but obviously you loose the immediate "Open and burn" functionality". Please tell us what you would like to do with this ISO and the reason for encryption.
Archival Encryption should be done by software like truecrypt. If you want ease of transfer, i would go with zip or rar with password protection.
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I don't hand out food, but I'll teach you how to fish.
CAGG: "So what you do is freeze the anti-freeze, wait... that wont work will it?"