Verify Trusted provider of a digital sign

Hello everyone, I need to make sure that a digital signature field was signed by a particular trusted provider. I'm getting the properties of the signature through var f = this.getField ("sign_professional"); var Info = f.signatureInfo (); but I can not get any data referring to the provider of that firm, (I'm not talking about the person who makes the signature, I'm talking about the trusted provider through which the signature was obtained), thank you very much!