Object File-based data library?

Some time ago I found a reference o开发者_如何学Gonline to a database system that stored data locally as encryptable, portable object files, but I cannot recall the name of it, and all the search keywords (object, file, database) are so generic the Google is not helping so much. I'm not even sure if I'm remembering it correctly now.

So the question: I would like to use a free library in C# that will allow me to store queryable objects (full graphs), transport them (import/ export/ clone) between systems with a simple file transfer protocol, and not require any infrastructure installation (like SQL Express/ MySQL/ PostgreSQL) outside the class library. Inherent encryption capability is a nice-to-have, but if necessary I will simply do that through a custom implementation. Any suggestions?

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Since nobody answered my question, I'll answer. @L.B pointed me in the right direction; I was looking for db4o.