I think ST's comment above sums it up: any obvious protection or encryption will in itself attract the attention of customs, and in some places Customs can detain you indefinitely until they're satisfied you've handed over all the goods.

The problem is not hiding the goods, the problem is getting through customs. That means being a sufficiently good smuggler that Customs don't know and are extremely unlikely to discover that there are hidden things. It's not enough to simply hide them and say "ha ha I win". So work-arounds like hidden partitions and the internet remain the most effective way for data that you really do want to get through.

AFAIK Customs always have the option of simply saying "no, you can't bring that in". At which point you can turn round or sometimes they let you dispose of the objectionable item. It's extremely unlikely that they will let you through after failing to obtain decrypted data that they've asked for.

My solution is simply not to travel to states with poor politics, like China and the US. That's cost me one possible job so far but I'd rather lose a job than my life. Unfortunately both the US and UK have demonstrated that China and Burma etc really have nothing to worry about when freeing up their media, torture and disappearance still work just fine in a "free" country. This is just another example...