"error:CERT_UNTRUSTED" when I add an accounts-password package

My platform is windows 7.I want to add the accounts-password package. But I got a “error:CERT_UNTRUSTED”.

This is all output error message.

AppData\Local.meteor\leaderboard>…\meteor add accounts-password

Unable to update package catalog (are you offline?)

If you are using Meteor behind a proxy, set HTTP_PROXY and HTTPS_PROXY environment variables or see this page for more details: https://github.com/meteor/meteor/wiki/Using-Meteor-behind-a-proxy

=> Errors while adding packages:

While downloading npm-bcrypt@0.7.8_2…: error: CERT_UNTRUSTED

Your package catalog may be out of date. Please connect to the internet and try again.

I don’t know how to fix this problem. Or is there a alternative manual way to add this accounts-password package. Have any suggestions? Many thanks.