What is a word for a person who trusts (someone else)?

Alfred trusts Bob.

In some contexts — especially legal or financial — we might call Bob a trustee. Following this vein (and pursuing a notion of generalization) what might we call Alfred? A truster?

Bonus question: Is there a name for the thing that Alfred trusts Bob with?

In working around this question I came up with a few other somewhat related concepts.

• guarantor. What do we call the recipient of the guarantee? The guaranteed? (Note the disambiguation required between the person who is being guaranteed something, and the object being guaranteed).
• contributor. What do we call the recipient of the contribution?

Are these examples of some broader set of English words (or ideas)?