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dguido's profile
Dan Guido
Dan Guido
Dan Guido
@dguido

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Dan Guido

@dguido

CEO @trailofbits, organizer @EmpireHacking, director @hack_secure. Open DMs.

Brooklyn, NY
trailofbits.com
Joined April 2008

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    1. Michael Koziarski‏ @nzkoz 21 Feb 2016
      Replying to @msolnik

      @msolnik @dguido @riskybusiness the exact hardware performance limit there is 80ms

      1 reply 0 retweets 0 likes
    2. Mathew Solnik‏ @msolnik 21 Feb 2016
      Replying to @nzkoz

      @nzkoz @dguido @riskybusiness on 64bit?

      2 replies 0 retweets 0 likes
    3. Michael Koziarski‏ @nzkoz 21 Feb 2016
      Replying to @msolnik

      @msolnik @dguido “The iteration count is calibrated so that one attempt takes approximately 80 milliseconds” https://www.apple.com/business/docs/iOS_Security_Guide.pdf …

      1 reply 0 retweets 0 likes
    4. Mathew Solnik‏ @msolnik 21 Feb 2016
      Replying to @nzkoz

      @nzkoz @dguido gotcha. Not sure if that's software or hardware on 64. You are right on 32 they could just increase/add another kbag layer.

      2 replies 0 retweets 1 like
    5. Michael Koziarski‏ @nzkoz 21 Feb 2016
      Replying to @msolnik

      @msolnik @dguido the key for pbkdf2 is in the enclave, there’s no key read API, so I’m 99.999% sure it’s pure hardware cost of 80ms.

      2 replies 0 retweets 2 likes
    6. Dan Guido‏ @dguido 21 Feb 2016
      Replying to @nzkoz

      @nzkoz @msolnik software can't lower the iteration count. Once you derive the key from a passcode, that's it, you have to deal.

      1 reply 0 retweets 0 likes
    7. Michael Koziarski‏ @nzkoz 21 Feb 2016
      Replying to @dguido

      @dguido @msolnik could lower the iteration count for future passcodes set on the device. But ya doesn’t help here, just future brute forcers

      1 reply 1 retweet 1 like
    8. Dan Guido‏ @dguido 21 Feb 2016
      Replying to @nzkoz

      @nzkoz @msolnik correct, but that's not the scenario we're talking about.

      1 reply 0 retweets 0 likes
    9. Mathew Solnik‏ @msolnik 21 Feb 2016
      Replying to @dguido

      @dguido @nzkoz while I don't disagree that if the iteration count is done in software making it much higher would increase the potential...

      1 reply 0 retweets 0 likes
    10. Mathew Solnik‏ @msolnik 21 Feb 2016
      Replying to @msolnik

      @dguido @nzkoz time needed. But it does not prevent the loading of a ramdisk/modded firmware which can be used to partially offload BF.

      1 reply 0 retweets 0 likes
      Dan Guido‏ @dguido 21 Feb 2016
      Replying to @msolnik

      @msolnik @nzkoz If PBKDF were benchmarked to 1s, it would take 2 years to break even a 5-char loweralphanum password

      11:12 PM - 21 Feb 2016
      1 reply 0 retweets 0 likes
        1. New conversation
        2. Dan Guido‏ @dguido 21 Feb 2016
          Replying to @dguido

          @msolnik @nzkoz IMHO iteration count is the strongest first line of defense Apple has they can easily modify in a sw update.

          3 replies 0 retweets 0 likes
        3. ash‏ @uglypackets 21 Feb 2016
          Replying to @dguido

          @dguido how does iteration count play with limitations in mobile compute power?

          1 reply 0 retweets 0 likes
        4. Dan Guido‏ @dguido 21 Feb 2016
          Replying to @uglypackets

          @uglypackets users only enter their passwords infrequently, especially if they use TouchID. It's a UX issue, not a power issue.

          1 reply 0 retweets 0 likes
        5. ash‏ @uglypackets 21 Feb 2016
          Replying to @dguido

          @dguido right, but UX hit is not insignificant, generations of phones have cpu variance. I'm curious how much of a delay hit you can take.

          1 reply 0 retweets 0 likes
        6. Dan Guido‏ @dguido 22 Feb 2016
          Replying to @uglypackets

          @uglypackets the iteration count is benchmarked against CPU performance for constant time outcome, i.e. 80ms

          0 replies 0 retweets 0 likes
        7. End of conversation

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