[o11c]

The main disadvantage of this is that most encryption libraries don't support serializing their state.

[fao_]

Eh, you could probably get away with it if you use BearSSL[0]. The only difficulty would be:

    These elements can be allocated anywhere in (writable) memory, e.g.
    heap, data segment or stack. They must not be moved while in use
    (they may contain pointers to each other and to themselves).

Which you could probably get around with by just keeping track of offsets and using mmap

[0]: https://www.bearssl.org/api1.html