Amazon DynamoDB InvalidSignatureException
It seems that your local system time might be incorrect. I've had a similar problem with AWS S3, where my system clock was skewed by 30 mins.
If you're running ubuntu, try updating your system time:
sudo ntpdate ntp.ubuntu.com
You can also restart your date service to solve the problem if you've already got ntpdate installed.
sudo service ntpdate stopsudo service ntpdate start
If you are using docker-machine on Mac, you can resolve with this command:
docker-machine ssh default 'sudo ntpclient -s -h pool.ntp.org'