verify.rb

    # BTW, the value here is not empty
    public_key = File.read(@public_key_path)
    data = params.permit!

    # Get the p_signature parameter & base64 decode it.
    signature = Base64.decode64(data['p_signature'])

    # Remove the p_signature parameter
    data.delete('p_signature')

    # Ensure all the data fields are strings
    data.each {|key, value| data[key] = String(value)}

    # Sort the data
    data_sorted = data.sort_by{|key, value| key}

    # and serialize the fields
    # serialization library is available here: https://github.com/jqr/php-serialize
    data_serialized = PHP.serialize(data_sorted, true)

    # verify the data
    digest   = OpenSSL::Digest::SHA1.new
    pub_key  = OpenSSL::PKey::RSA.new(public_key).public_key
    verified = pub_key.verify(digest, signature, data_serialized)

    # outputting false
    verified #=> false