Handle edge cases in encryption

**Problem**
When working with parsers, 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 parser error-handling paths and reviewing how failures are currently reported. Done means parser edge cases produce more descriptive error messages and the resulting behavior is verified.

Written by the indexing model from the issue text.