One IdP to rule (or breach) them all: How identity access management tools can secure -- or destroy -- your kingdom
When we want to secure something highly valuable, say, a bag of ancient Spanish coins worth millions, we think of locking it behind as many layers as possible. For example, you might put it in a safe deposit box in a bank vault, nestled safely inside the institution that is itself blanketed with redundant physical security controls.
Source: betanews.com