Hint to resolve certificate problems

npm install (0.8.2) provokes the following error for me

npm install
npm http GET https://registry.npmjs.org/jsdom
npm http GET https://registry.npmjs.org/jsdom
npm http GET https://registry.npmjs.org/jsdom
npm ERR! Error: SSL Error: SELF_SIGNED_CERT_IN_CHAIN
npm ERR!     at ClientRequest.<anonymous> (/usr/lib/nodejs/npm/node_modules/requ                                                                                                                est/main.js:440:26)
npm ERR!     at ClientRequest.g (events.js:185:14)
npm ERR!     at ClientRequest.EventEmitter.emit (events.js:88:17)
npm ERR!     at HTTPParser.parserOnIncomingClient [as onIncoming] (http.js:1445:                                                                                                                7)
npm ERR!     at HTTPParser.parserOnHeadersComplete [as onHeadersComplete] (http.                                                                                                                js:111:23)
npm ERR!     at CleartextStream.socketOnData [as ondata] (http.js:1356:20)
npm ERR!     at CleartextStream.CryptoStream._push (tls.js:396:27)
npm ERR!     at SecurePair.cycle (tls.js:750:20)
npm ERR!     at EncryptedStream.CryptoStream.write (tls.js:131:13)
npm ERR!     at Socket.ondata (stream.js:38:26)
npm ERR!  [Error: SSL Error: SELF_SIGNED_CERT_IN_CHAIN]
npm ERR! You may report this log at:
npm ERR!     <http://github.com/isaacs/npm/issues>
npm ERR! or email it to:
npm ERR!     <npm-@googlegroups.com>

npm ERR! System Linux 3.8.0-39-generic
npm ERR! command "nodejs" "/usr/bin/npm" "install"
npm ERR! cwd /home/vagrant/mathoid/MathJax-node
npm ERR! node -v v0.8.2
npm ERR! npm -v 1.1.39
npm ERR! message SSL Error: SELF_SIGNED_CERT_IN_CHAIN
npm ERR!
npm ERR! Additional logging details can be found in:
npm ERR!     /home/vagrant/mathoid/MathJax-node/npm-debug.log
npm ERR! not ok code 0

running npm config set ca "" resolves this problem