We have quantum computers and we also have Shor's algorithm. So:

  1. Why isn't RSA cracked yet?
  2. What are the current quantum computers lacking?
  • $\begingroup$ Who said it isn't cracked? If someone bothered to do through the effort of cracking it with the intent to misuse it, why would such a person ever announce that? It would be very, very dangerous to announce such a thing even if you did it without any malicious intent whatsoever. $\endgroup$ – dtech Jun 5 '16 at 17:59
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    $\begingroup$ To break RSA-2048 you need about 4000 perfect qubits. I think the best quantum computers are around 5 bits at the moment. $\endgroup$ – CodesInChaos Jun 5 '16 at 18:12
  • $\begingroup$ @CodesInChaos that's exactly what I needed to know! Do you have any sources for that? Isn't D-Wave operating at 128-qubits? And about 1.5n qubits would be required for RSA-2048 (see paper by Zalka) with n being the amount of digits. So that'd be 926 qubits. $\endgroup$ – Kevin Van Ryckegem Jun 5 '16 at 18:39
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    $\begingroup$ @KevinVanRyckegem D-Wave computers are incapable of running Shor's algorithm, so they can't attack RSA. They're limited to one particular optimization problem. $\endgroup$ – CodesInChaos Jun 5 '16 at 18:41
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    $\begingroup$ Also see: "Now that quantum computers have been out for a while, has RSA been cracked?" $\endgroup$ – SEJPM Jun 5 '16 at 19:05