1. A method, comprising: obtaining biometric data; selecting a first biometric descriptor at a first level of a hierarchy of biometric descriptors using the biometric data, wherein the first biometric descriptor is associated with a subset of biometric descriptors at a second level of the hierarchy of biometric descriptors; obtaining a first key component associated with the first biometric descriptor; selecting a second biometric descriptor from the subset of biometric descriptors at the second level using the first biometric descriptor and the biometric data; obtaining a second key component associated with the second biometric descriptor; and generating a cryptographic key using at least the first key component and the second key component.