This might be a repeated question, but I was not able to find a conversation, What is the SAMLResponse Encoding Format siteminder uses?
As per the FWSTrace.log "SAML2 Single Sign-On Service sending base64 SAML Response"
So, is it base64 encoding?
Is there is a way to change it to UTF-8 format?
A SAML protocol message is form-encoded by applying the
base-64 encoding rules to the XML representation of the message and placing the result in a hidden form
control within a form as defined by [HTML401] Section 17. The HTML document MUST adhere to the
XHTML specification, [XHTML]. The base64-encoded value MAY be line-wrapped at a reasonable length
in accordance with common practice.
This is part of SAML specification. You can not and shall not wish to change to UTF-8 format.
Hope this answer your question.
Thanks for your suggestion.