This is a feature request to allow clients to mix in additional data to the chrome.enterprise.platformKeys apis, which could help other protocol exchanges. 

currently, the chrome.enterprise.platformKeys looks like the following.

chrome.enterprise.platformKeys.challengeMachineKey = function(challenge, callback) { }
chrome.enterprise.platformKeys.challengeUserKey = function(challenge, registerKey, callback) { }

Proposed change
chrome.enterprise.platformKeys.challengeMachineKey = function(challenge, clientData, callback) { }
chrome.enterprise.platformKeys.challengeUserKey = function(challenge, registerKey, clientData, callback) { }

The clientData will be signed and itself also sent along with the signed response. 

For more details with the bug, please refer to b/32613818