This story was posted to Hacker News in May: https://news.ycombinator.com/item?id=5661576 https://news.ycombinator.com/item?id=5661576 http://arxiv.org/abs/13

This story was posted to Hacker News in May: https://news.ycombinator.com/item?id=5661576 https://news.ycombinator.com/item?id=5661576 http://arxiv.org/abs/1305.0305?utm_source=feedly http://arxiv.org/abs/1305.0305?utm_source=feedly Read the arXiv paper: it's quite short and not very technical. The BB84 protocol used is described in a lower comment by 'harshreality. It is secure against any purely classical attacker; Preskill and Shor give a (highly involved) proof of security here: http://arxiv.org/pdf/quant-ph/0003004 http://arxiv.org/pdf/quant-ph/0003004 However, the BB84 protocol used is susceptible in its original form to quantum man-in-the-middle attacks, eg: http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=5234678&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D5234678 http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=523467... LANL probably thinks this is infeasible at the moment -- with good reason: quantum computing equipment is extraordinarily difficult to obtain or produce, and so it would be very hard indeed to carry out such an attack in secret. There are approaches to dispelling quantum MitM, such as a paper I've posted below.