example.rb

# Generate your password in your preferred manner, such as SecureRandom.base64(30)
node[:my_super_secret_password] ||= NodeEncryption.encrypt_value("super_secret!")
# Later on, recover the password
my_super_secret_password = NodeEncryption.decrypt_value(node[:my_super_secret_password])

node_encryption.rb

module NodeEncryption
  def self.encrypt_value(value)
    secret = Chef::EncryptedDataBagItem.load_secret("/etc/chef/secret")
    Chef::EncryptedDataBagItem::Encryptor.new(value, secret).for_encrypted_item
  end

  def self.decrypt_value(value, item_name)
    secret = Chef::EncryptedDataBagItem.load_secret("/etc/chef/secret")
    Chef::EncryptedDataBagItem::Decryptor.for(value, secret).for_decrypted_item
  end
end