# Signature invalid
**URL:** https://community.zymbit.com/t/signature-invalid/1574
**Category:** Getting Started
**Created:** [September 13, 2023, 6:37am UTC](https://community.zymbit.com/t/signature-invalid/1574 "2023-09-13T06:37:07Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@Daniel](https://community.zymbit.com/u/Daniel)
#### Post date: [September 13, 2023, 6:37am UTC](https://community.zymbit.com/t/signature-invalid/1574/1 "2023-09-13T06:37:07Z")
Hi, I’m using Raspbian GNU/Linux 10 (buster) on a raspberry pi 3b and upgrading the packages by `sudo apt update`, but the update failed due to the signature verification failed. Am I doing something wrong or what’s happening? Thanks.
Here’s the log:
```auto
pi@raspberrypi:~ $ sudo apt update
Hit:1 http://raspbian.raspberrypi.org/raspbian buster InRelease
Hit:2 http://archive.raspberrypi.org/debian buster InRelease
Get:3 https://zk-sw-repo.s3.amazonaws.com/apt-repo-buster buster InRelease [2500 B]
Err:3 https://zk-sw-repo.s3.amazonaws.com/apt-repo-buster buster InRelease
The following signatures were invalid: EXPKEYSIG CAA5E9C8755D21A0 scott@zymbit.com
Fetched 2500 B in 2s (1136 B/s)
Reading package lists... Done
Building dependency tree
Reading state information... Done
131 packages can be upgraded. Run 'apt list --upgradable' to see them.
W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: https://zk-sw-repo.s3.amazonaws.com/apt-repo-buster buster InRelease: The following signatures were invalid: EXPKEYSIG CAA5E9C8755D21A0 scott@zymbit.com
W: Failed to fetch https://zk-sw-repo.s3.amazonaws.com/apt-repo-buster/dists/buster/InRelease The following signatures were invalid: EXPKEYSIG CAA5E9C8755D21A0 scott@zymbit.com
W: Some index files failed to download. They have been ignored, or old ones used instead.
```
---
### Author:  [@Bob\_of\_Zymbit](https://community.zymbit.com/u/Bob_of_Zymbit)
#### Post date: [September 13, 2023, 3:12pm UTC](https://community.zymbit.com/t/signature-invalid/1574/2 "2023-09-13T15:12:32Z")
Did you try this?
https://docs.zymbit.com/troubleshooting/general/#expired-gpg-key-preventing-access-to-repository
---
### Author:  [@Daniel](https://community.zymbit.com/u/Daniel)
#### Post date: [September 15, 2023, 9:29am UTC](https://community.zymbit.com/t/signature-invalid/1574/3 "2023-09-15T09:29:43Z")
Yes, it works. Thanks!