reCAPTCHA custom form parameter names

Question

Is possible to customize reCAPTCHA form parameters (recaptcha_challenge_field and recaptcha_response_field) so that they are called differently?

Basically I want the form parameter recaptcha_challenge_field to be called captchaId, and recaptcha_response_field to be called captchaUserResponse.

I want them renamed so I can abstract the captcha implementation... when a request arrives on

POST /mysite/userSignup

I don't want to bother with captcha implementation (reCaptcha, or something else in the future) - extracting the right parameters for the right captcha implementation, I want to unify those parameter names.

Now my request looks like this:

POST /mysite/userSignup HTTP/1.1
Host: localhost:80
Connection: keep-alive
Content-Length: 416
Cache-Control: max-age=0
Origin: http://localhost:80
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/536.5 (KHTML, like Gecko) Chrome/19.0.1084.46 Safari/536.5
Content-Type: application/x-www-form-urlencoded
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Referer: http://localhost:8080/mysite/signup/form.html
Accept-Encoding: gzip,deflate,sdch
Accept-Language: en-US,en;q=0.8,hr;q=0.6
Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3

email:testUser%40gmail.com
username:testUser
password:test
password2:test
forename:Test
surname:User
recaptcha_challenge_field:<google generated challange>
recaptcha_response_field:<user typed captcha answer>
submit:Submit

But I want it to look like this:

POST /mysite/userSignup HTTP/1.1
Host: localhost:80
Connection: keep-alive
Content-Length: 416
Cache-Control: max-age=0
Origin: http://localhost:80
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/536.5 (KHTML, like Gecko) Chrome/19.0.1084.46 Safari/536.5
Content-Type: application/x-www-form-urlencoded
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Referer: http://localhost:8080/mysite/signup/form.html
Accept-Encoding: gzip,deflate,sdch
Accept-Language: en-US,en;q=0.8,hr;q=0.6
Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3

email:testUser%40gmail.com
username:testUser
password:test
password2:test
forename:Test
surname:User
captchaId:<google generated challange>
captchaUserResponse:<user typed captcha answer>
submit:Submit

An elegant way would be to specify those form parameter names like this:

<script>
   var RecaptchaOptions = {
      recaptcha_challenge_field_formparam_name : 'captchaId',
      recaptcha_response_field_formparam_name: 'captchaUserResponse'
   };
</script>

---

If this isn't possible, what workaround do you suggest?