SecureRandom.uuid.gsub(/[d-]/) { |x| (x.ord + 55).chr }
# => "jpkgelfndpcoadkbgidbobddifkckodalmkj"

def get_random_string(length=5)
  source=("a".."z").to_a + ("A".."Z").to_a
  key=""
  length.times{ key += source[rand(source.size)].to_s }
  return key
end