new encryption scheme

[zelig]

extend encryption stream cipher entropy scope to optimise storage overhead in PACs

motivation

• erasure repairs
• encrypted SOCs
• mupltimedia streaming
• repeatable upload

sub-tasks

• encrypted reference redefinition
• seed-based repeatable encryption
• selective disclosure

[zsgsp]

The initial idea has to be sketched as a WIP SWIP before handing over to others.
More parts of Multimedia streaming depend on this.