Processing
Reference Validation
  - locate object and apply Transformsto the specified resource based on eachObjectReference(s)
    in theSignedInfoelement.
- calculate digest over each transformed signed object(s) 
- compare value against DigestValueinSignedInfofor each
    reference (if any mismatch, validation fails).
Signature Validation
  - canonicalize the SignedInfoelement based on theCanonicalizationMethod,
    if any, inSignedInfo.
- obtain the validation keying info from KeyInfoor externally.
- validate the SignatureValuebased on theSignatureMethodin
    theSignedInfo