It seems that knox doesn't support signature v4 (http://docs.aws.amazon.com/general/latest/gr/signature-version-4.html). On Frankfurt data center (eu-central-1), it is required, and I can't get knox to work with it. Trying to get a list of files in bucket results following error:

'The authorization mechanism you have provided is not supported. Please use AWS4-HMAC-SHA256.'

Here is the sample code:

var knox = require('knox');

var client = knox.createClient({
    key: '*****'
  , secret: '*****'
  , bucket: 'my-bucket'
  , region: 'eu-central-1'
});

client.list({}, function(err, data){
    console.log(err, data);
});