How can I send a single string parameter?

[dio-brando]

Hello, Im a Korean android developer and new with swift4.

I need to post a url as restful api, and it takes parameter as a single string body that is encrypted like 'QlDlLNnhk6N81QfAXfTVT09Z5UOHO/uzXax26Z4bp5U='.

It will be decrypted as a JSON string like { "id": "abc", "pwd":"1234" }, so i cannot put just data:[ key : value ].

Is there any way to send single string? or should i find another http library?