app.rb

require "bundler"
require "pp"
Bundler.require

description = RDF::Turtle::Reader.new(STDIN)
graph = RDF::Graph.new << description
query = graph.query(predicate: RDF::URI('http://xmlns.com/wot/0.1/assurance')).first
subject_uri = query && query.subject.to_s
signature_uri = query && query.object.to_s
if signature_uri &&  signature_uri =~ /urn:ipfs:(.*)/
    signature = RestClient.get("http://ipfs.io/ipfs/#{$1}").body
    puts signature
end
if subject_uri && subject_uri =~ /urn:ipfs:(.*)/
    profile = RestClient.get("http://ipfs.io/ipfs/#{$1}").body
    puts profile
    graph = RDF::Graph.new << RDF::Turtle::Reader.new(profile)
    query = graph.query(predicate: RDF::URI('http://xmlns.com/wot/0.1/hasKey')).first
    public_key_uri = query && query.object.to_s
    public_key = RestClient.get(public_key_uri).body
    puts public_key
end

crypto = GPGME::Crypto.new
GPGME::Key.import(public_key)
crypto.verify(GPGME::Data.new(signature), signed_text: profile){|signature| p signature.inspect; p signature.valid? }

console input

cat ipfs.ttl |ruby app.rb

ipfs.ttl

<urn:ipfs:QmYJXcwDU72gQDSbNFo41Z7sLJU9LVivRx485r41owmXWY> <http://xmlns.com/wot/0.1/assurance> <urn:ipfs:QmbdooNUQM3efGjPByB485CicqZFZRbxFGCmauzJkUEAbb> .