Remove deprecated cryptography implementation

[michaelWuensch]

Description

This removes the cryptography implementation that was used prior to v0.4.0-beta. As a result, users updating from versions prior to 0.4.0-beta to the upcoming version v0.5.1-beta will have their app reset and will have to connect to their node again.

Motivation and Context

Remove deprecated code and to keep the code simple and easier auditable.

How Has This Been Tested?

On my S9

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [x] Chore

Checklist:

• [x] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [x] I have read the Contribution document.
• [ ] I have added tests to cover my changes.
• [x] All new and existing tests passed.