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It better to add two different devices with different secrets to the account, than both sharing the same secret. This reduces the chances that something goes wr
by DownGoat 7y ago
It better to add two different devices with different secrets to the account, than both sharing the same secret. This reduces the chances that something goes wrong when a device is lost, or removed. The user can the remove the other device with much less risk of locking themselves out of the account. It also might provide some info in the cases where a secret is leaked, as it can be tracked to the specific device.
There is no real security risk of the devices having the same secret, or in adding a backup device. It is really a usability thing, the biggest pain point a user will experience with TOTP is when they are switching phones, or when they lose one. Decreasing the friction here can greatly improve the security of the system.
- jandrese 7y agoIf the service supports that then it's fine. A lot of services only support a single TOTP key per account though. There's a small risk in provisioning multiple TOTP keys on one account too. Each one reduces the search space for a brute force attack. Add in allowances for drifting clocks and a lack of account lockout for missed attempts and you might open up the window just enough for a brute force attack to be successful.