woocommerce _order_key and post_password

Hi. A friend asked me to help him migrate some data to WP database. I would like to ask for some help for two tables
1. In case of orders in the WP_POSTS table where post_type=’shop_order’, how is the key generated in the post_password column ?
2. In the wp_postmeta table, where meta_key = ‘_order_key’ for the order mentioned above, there is a different key generate, its seems its being generated with the same algorithm, but i don’t know which one and why are they different ?

Please advice me.
Thanks