A multi-party security protocol that incorporates biometric-based 
authentication and withstands attacks against any single party (e.g., 
mobile phone, cloud, or the user). The protocol involves the function split between mobile and cloud and the mechanisms to chain-hold the secrets. A 
key generation mechanisms binds secrets to a specific device or URL (
uniform resource locator) by adding salt to a master credential. An inline 
CAPTCHA (Completely Automated Public 
Turing test to tell Computers and Humans Apart) handling mechanism uses the same sensor modality as the 
authentication process, which not only improves the 
usability, but also facilitates the 
authentication process. This architecture further enhances existing overall 
system security (e.g., handling untrusted or compromised cloud service, phone being lost, impersonation, etc.) and also improves the 
usability by automatically handling the 
CAPTCHA.