fix(mypy): type annotations for cipher algorithms

[dhruvmanila]

Issue: #4052

❯ mypy --ignore-missing-imports --strict ciphers/
Success: no issues found in 39 source files

Describe your change:

• Add an algorithm?
• Fix a bug or typo in an existing algorithm?
• Documentation change?

Checklist:

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized.
• I know that pull requests will not be merged if they fail the automated tests.
• This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
• All new Python files are placed inside an existing directory.
• All filenames are in all lowercase characters with no spaces or dashes.
• All functions and variable names follow Python naming conventions.
• All function parameters and return values are annotated with Python type hints.
• All functions have doctests that pass the automated testing.
• All new algorithms have a URL in its comments that points to Wikipedia or other similar explanation.
• If this pull request resolves one or more open issues then the commit message contains Fixes: #{$ISSUE_NO}.

[cclauss]

Don’t we want the GitHub Action updated to prove that the directory is fixed?

Should we use mypy —strict in our tests?

[dhruvmanila]

Don’t we want the GitHub Action updated to prove that the directory is fixed?

Done

Should we use mypy —strict in our tests?

I prefer to be strict in type checking but we should take it gradually. The --strict flag include the following checks:

    --strict                  Strict mode; enables the following flags: --warn-
                              unused-configs, --disallow-any-generics,
                              --disallow-subclassing-any, --disallow-untyped-
                              calls, --disallow-untyped-defs, --disallow-
                              incomplete-defs, --check-untyped-defs, --disallow-
                              untyped-decorators, --no-implicit-optional,
                              --warn-redundant-casts, --warn-unused-ignores,
                              --warn-return-any, --no-implicit-reexport,
                              --strict-equality

In short, it won't allow any variable, function, decorators or class to be untyped. Most of the options should be configured via mypy.ini file which I will add in the upcoming PR. We can then gradually add options to make mypy stricter.

[cclauss]

Awesome work! Thanks for doing this.