WALK4MEBackup and Encryption
This page describes the backup and encryption in place on the Walk4Me server, for participants, researchers, review boards and funders. The Data security statement covers the rest of how Walk4Me protects data.
01At a glance
Daily backupsEvery day, a backup of the whole server is taken automatically, and the last 35 days are kept.
Encrypted at restThe server’s disks and its daily backups are encrypted with AES-256.
RecoverableData can be restored to any of the last 35 daily backups, from a single file up to the whole server.
WhereAmazon Web Services, us-west-1 (Northern California). Backups are kept in the same region.
02What is covered
| Part of the server | What it holds |
|---|---|
| System disk | The operating system, the web server, the Walk4Me software, user accounts and logs |
| Project data | All project data: sensor recordings, videos and processed results |
Both are backed up together, so a backup always shows the server as it was at one moment. Recordings still waiting on a participant’s phone are not on the server yet; the app keeps them on the phone until they have been uploaded.
03Backups
- How often: once a day, automatically, at night (Pacific time). The portal stays available while a backup is taken.
- How long they are kept: the last 35 daily backups (five weeks). Older ones are deleted automatically.
- How they work: backups are Amazon EBS snapshots, managed by an AWS backup policy. Each one stores only what changed since the one before, and removing an old backup never removes data a newer one needs.
- Where they are kept: AWS stores them across several data centres in the us-west-1 region. They are not copied to a second region, so a region-wide outage would affect the server and its backups alike.
- Who can use them: only the Walk4Me administrators, through the AWS account, which is protected by multi-factor authentication.
04Recovery
| Goal | What it means for Walk4Me |
|---|---|
| Recovery point | At most 24 hours of changes could be lost: data is restored to the last daily backup. |
| Recovery time | About 1 to 4 hours to restore the whole server; single files or folders can be restored while the portal keeps running. |
| During an outage | Phones keep recording offline and upload once the server is back; only live streaming pauses. |
05Encryption at rest
- Method: Amazon EBS encryption, AES-256, with a key managed by AWS Key Management Service. Encryption happens in AWS’s storage hardware, so it does not slow the portal.
- What it covers: both server disks and every backup made from them. Every new disk in the account’s region is encrypted automatically.
- On the phone: recordings stay in the app’s private storage, which iOS encrypts, and are excluded from iCloud and computer backups until they are uploaded.
- In transit: every connection uses HTTPS (TLS 1.2 or 1.3). See the Data security statement for the full picture.
06Cost
Encryption adds no cost: Amazon EBS encryption and the AWS-managed key are free, and encrypted disks cost the same as unencrypted ones. Backups are charged by AWS as snapshot storage.
Version 2.0 · 7 November 2026