The request for release must set forth the grounds for release, describe the property to be released, be executed under oath and be filed with the levying officer, together with a copy thereof.
(CCP 493.040(b)(c))
In the case of an assignee, the request shall include two copies of the general assignment for the benefit of creditors.
In the case of a trustee, interim trustee, or debtor in possession, the request shall include a certified copy of the petition in bankruptcy, together with a copy thereof.
If immediate release of the attachment is sought, the request shall be accompanied by an undertaking to pay the plaintiff any damages resulting from an improper release of the attachment, in the amount of the plaintiff s claim to be secured by the attachment, executed by an admitted surety insurer.
(CCP 493.040(d))
It is the duty of the sheriff to see that he has in his hands a proper bond before he releases property under attachment. (Sparks v. Buckler 14 CA 2d 213 – cite available through CMB Ops)
Information regarding certificates of authority from the Insurance Commissioner is available from California Department of Insurance.