Trusted system 1: crypto

{  :F a :Request.
   :F log:includes { :str acc:endorsement
                [acc:signature :sig; acc:key :k]}.
   :k crypto:verify ([is crypto:md5 of :str] :sig).
   :str log:parsedAsN3:G
} 
 => { :G acc:requestSupportedBy :k }.