The `read` builtin accepts backslash notation for common non-printing
characters by default, like `\t` and `\n`. This requires that any
literal backslashes must also be escaped as `\\`.

Given that `gpg -e` does not interpret input, the `read` invocations are
changed to do the same.

Also, the right hand side of an `==` comparison within `[[ ]]` must be
quoted in order to suppress pattern metacharacter expansion. Quoting the
bash manual:

    When the == and != operators are used, the string to the right of
    the operator is considered a pattern and matched according to the
    rules described below under Pattern Matching.