BACKGROUND: Mobile Health (mHealth) proposes health care delivering anytime and 
anywhere. It aims to answer several emerging problems in health services, 
including the increasing number of chronic diseases, high costs on national 
health services, and the need to provide direct access to health services, 
regardless of time and place. mHealth systems include the use of mobile devices 
and apps that interact with patients and caretakers. However, mobile devices 
present several constraints, such as processor, energy, and storage resource 
limitations. The constant mobility and often-required Internet connectivity also 
exposes and compromises the privacy and confidentiality of health information.
OBJECTIVE: This paper presents a proposal, construction, performance evaluation, 
and validation of a data encryption solution for mobile health apps (DE4MHA), 
considering a novel and early-proposed cooperation strategy. The goal was to 
present a robust solution based on encryption algorithms that guarantee the best 
confidentiality, integrity, and authenticity of users health information. In 
this paper, we presented, explained, evaluated the performance, and discussed 
the cooperation mechanisms and the proposed encryption solution for mHealth 
apps.
METHODS: First, we designed and deployed the DE4MHA. Then two studies were 
performed: (1) study and comparison of symmetric and asymmetric 
encryption/decryption algorithms in an mHealth app under a cooperation 
environment, and (2) performance evaluation of the DE4MHA. Its performance was 
evaluated through a prototype using an mHealth app for obesity prevention and 
cares, called SapoFit. We then conducted an evaluation study of the mHealth app 
with cooperation mechanisms and the DE4MHA using real users and a real 
cooperation scenario. In 5 days, 5 different groups of 7 students selected 
randomly agreed to use and experiment the SapoFit app using the 7 devices 
available for trials.
RESULTS: There were 35 users of SapoFit that participated in this study. The 
performance evaluation of the app was done using 7 real mobile devices in 5 
different days. The results showed that confidentiality and protection of the 
users' health information was guaranteed and SapoFit users were able to use the 
mHealth app with satisfactory quality. Results also showed that the app with the 
DE4MHA presented nearly the same results as the app without the DE4MHA. The 
performance evaluation results considered the probability that a request was 
successfully answered as a function of the number of uncooperative nodes in the 
network. The service delivery probability decreased with the increase of 
uncooperative mobile nodes. Using DE4MHA, it was observed that performance 
presented a slightly worse result. The service average was also slightly worse 
but practically insignificantly different than with DE4MHA, being considered 
negligible.
CONCLUSIONS: This paper proposed a data encryption solution for mobile health 
apps, called DE4MHA. The data encryption algorithm DE4MHA with cooperation 
mechanisms in mobile health allow users to safely obtain health information with 
the data being carried securely. These security mechanisms did not deteriorate 
the overall network performance and the app, maintaining similar performance 
levels as without the encryption. More importantly, it offers a robust and 
reliable increase of privacy, confidentiality, integrity, and authenticity of 
their health information. Although it was experimented on a specific mHealth 
app, SapoFit, both DE4MHA and the cooperation strategy can be deployed in other 
mHealth apps.