free memory encryption, multiple rewrites, and used memory encryption

[jaredm]

I am trying to get around with encryption. What programs would anyone 
recommend for linux that produces good encryption. (the kind that is 
hard to crack?) Also, I realize these days that when data is "erased" on 
your hard drive the links pointing to area in memory where your data is 
stored is erased, not the actual data. Is there someway to encrypt swap 
memory and free disk memory? There are also ways data can be restored on 
your computer by doing some sort of quantum analysis, which means you 
might have to encrypt several times.