Handle edge cases in encryption

**Problem**
When working with store, the error messages could be more descriptive.

**Suggestion**
Improve error handling and add detailed error messages.

**Context**
This would help with debugging and maintenance.

No files, tests, or entry points are named. Start by locating the store and encryption error-handling paths, then identify the edge cases currently producing unhelpful messages; done means those cases report detailed, useful errors and the relevant checks pass.

Written by the indexing model from the issue text.