if timestamp.to_i(16) < (opts[:now] or db_current_time.to_i)
raise Blob::InvalidSignatureError.new 'Signature expiry time has passed.'
end
if timestamp.to_i(16) < (opts[:now] or db_current_time.to_i)
raise Blob::InvalidSignatureError.new 'Signature expiry time has passed.'
end