Offline synchronization support

[magp18]

What feature do you want to improve? Have a way of synchronize data offline with other devices. E.g. Health worker going to somewhere rural (being offline) would be able to synchronize data from other offline devices. He then could go to the main health facility, go online and synchronize with the main server.

Describe the improvement you'd like Offline synchronization of data between two devices. Does not have to be bidirectional flow of data.

Describe alternatives you've considered Download the data locally and the Health worker willing to collect the data would aggregate the data from every device in an USB key. He would then go to the main health facility and synchronize the collected data with the server.

Additional context Mostly for full offline settings.

[garethbowen]

Hi @magp18 ! This is very well aligned with our goal of reaching the hardest to reach places.

Mostly for full offline settings.

In this scenario would the remote user ever have internet access, or always rely on the mobile health worker to replicate?

Does not have to be bidirectional flow of data.

Many CHT functions rely on bidirectional replication so that changes made on the server end up getting back to the user. This means expected flows would fail in unpredictable ways. If the remote user has occasional (say, monthly?) internet access this may be acceptable, but to never have access would make this challenging.

There are also some challenges about data security, because it's difficult to prove identity while offline, so if a random passerby requested the data how would the CHT know to block them?

One option I have been thinking about is instead of using regular Couch/Pouch replication to achieve this, use an encrypted packet of data which can only be decrypted by the server. Then when the mobile health worker has a connection this is submitted to the server. The same can happen in reverse with the data being sent to the remote health worker being encrypted and downloaded on to the device. I think this is similar to your "alternative" approach above.

I think this is a great topic, and could use some community discussion. Would you mind posting this to the community forum for additional visibility?

[delcroip]

Here my 2 cents comments (I am a colleague of @magp18 )

Regarding the security, could it be possible to use a server public key to encrypt the data on the APP

• Cert either from https handshake
• certificate downloaded as part of the config (ideally linked to the user)

In addition a signature from the user "exporting the data" seems important, I would think of something like either a

• hash of the username + passwordhash + salt
• using a userspecific certificate

in case of sync from the server, the data could be encrypted with the private SSL key of the server

Regarding the data format, I don't really see security issue (mobile --> Server), for the otherway arround (server to app) it depends on the ACL/encryption in place on the app level:

• fulldb: "simpler" as it would be just db merge, less coding involved but can become too big
• specific bundle: "lighter" as only the relevant data will be moved: risk of data inconsistencies

br

[magp18]

In this scenario would the remote user ever have internet access, or always rely on the mobile health worker to replicate?

The person collecting all the data would have internet access as soon as he comes back to the main facility. The community health workers, assessing the patients in their devices would be fully offline if ever online.

Many CHT functions rely on bidirectional replication so that changes made on the server end up getting back to the user. This means expected flows would fail in unpredictable ways. If the remote user has occasional (say, monthly?) internet access this may be acceptable, but to never have access would make this challenging.

Yes he (the person collecting data from all devices) would have access to internet periodically.

There are also some challenges about data security, because it's difficult to prove identity while offline, so if a random passerby requested the data how would the CHT know to block them? One option I have been thinking about is instead of using regular Couch/Pouch replication to achieve this, use an encrypted packet of data which can only be decrypted by the server. Then when the mobile health worker has a connection this is submitted to the server. The same can happen in reverse with the data being sent to the remote health worker being encrypted and downloaded on to the device. I think this is similar to your "alternative" approach above. I think this is a great topic, and could use some community discussion. Would you mind posting this to the community forum for additional visibility?

I think this is a very good point. Thanks for that suggestion, encrypting data might be a good solution. I will follow your advice and open it for discussion in the forum to see everyone's ideas. Thanks!

[magp18]

I am not even sure if this would be at cht-android level or cht-core. I guess it would make more sense to have it in cht-core no? Otherwise I don't know how to get to the data and export it

[garethbowen]

@magp18 Yeah it sort of needs to be in both, because android will handle the connection to the other device, and cht-core will provide the data. For now I think the forum is the right place to discuss what this would look like and to get more information about what the community needs.