def rsa_sha1_signature
      private_key = OpenSSL::PKey::RSA.new(@attributes['consumer_secret'])
      Base64.encode64(private_key.sign(OpenSSL::Digest::SHA1.new, signature_base)).gsub(/\n/, '')
    end
def rsa_sha1_signature
      private_key = OpenSSL::PKey::RSA.new(@attributes['consumer_secret'])
      Base64.encode64(private_key.sign(OpenSSL::Digest::SHA1.new, signature_base)).gsub(/\n/, '')
    end
signature, with method RSA-SHA1. section 3.4.3

 @return [String]