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RichFelker's profile
Rich Felker
Rich Felker
Rich Felker
@RichFelker

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Rich Felker

@RichFelker

Yeah, I do @musllibc, FOSS & infosec stuff. But now is not the time for a mostly-/only-tech Twitter feed.

musl-libc.org
Joined March 2014

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    1. Peter Todd‏ @peterktodd Apr 17
      Replying to @peterktodd @CopperheadOS and

      As for being hardware bound without some kind of private key in the hardware, I don't see how that's possible. Any design w/o a private key in the hardware can be simulated externally. The only loophole here is if your hardware *is* the cheapest possible implementation.

      3 replies 0 retweets 1 like
    2. CopperheadOS‏ @CopperheadOS Apr 17
      Replying to @peterktodd @spudowiar and

      It's supposed to be truly hardware-bound with a private key for at least one of the low-level primitives in hardware. That's what iPhones and other phones like Pixels claim to be the status quo already. An adversary can certainly extract that key from the hardware though.

      1 reply 0 retweets 1 like
    3. CopperheadOS‏ @CopperheadOS Apr 17
      Replying to @CopperheadOS @peterktodd and

      This isn't something that's intended to be inherently / theoretically secure against an attacker performing an offline brute force attack. The feature has succeeded if doing an offline brute force requires sending a device to a lab to perform an expensive extraction process.

      1 reply 0 retweets 0 likes
    4. CopperheadOS‏ @CopperheadOS Apr 17
      Replying to @CopperheadOS @peterktodd and

      It's succeeding in this case. There's a widely available tool for cracking the encryption but it only performs an online brute force attack and apparently not even at the full throughput that the device is documented as being able to do key derivation.

      2 replies 0 retweets 2 likes
    5. Peter Todd‏ @peterktodd Apr 17
      Replying to @CopperheadOS @spudowiar and

      I'm not sure we're in any disagreement here... If anything, the fact that Apple's passcode strengthening isn't designed to withstand that attack makes it all the more important to understand what backup options you have if you need better security than that.

      2 replies 0 retweets 1 like
    6. Peter Todd‏ @peterktodd Apr 17
      Replying to @peterktodd @CopperheadOS and

      That's precisely why I asked how many iterations the KDF was doing. It's also why I said elsewhere in the thread that Apple might have been smart to also do a parallel CPU/RAM-bound KDF while the secure hardware one was running.

      1 reply 0 retweets 2 likes
    7. Matthew Green‏ @matthew_d_green Apr 17
      Replying to @peterktodd @CopperheadOS and

      Apple’s entire security posture is based around catering to a vast majority of users who won’t use strong passcodes. Six digits isn’t going to be secure at any level of KDF complexity.

      1 reply 0 retweets 1 like
    8. Matthew Green‏ @matthew_d_green Apr 17
      Replying to @matthew_d_green @peterktodd and

      For the rest of the world who *are* experts, maybe it’s just easier for those people to memorize strong 50-80 bit level passcodes.

      2 replies 0 retweets 2 likes
    9. CopperheadOS‏ @CopperheadOS Apr 17
      Replying to @matthew_d_green @peterktodd and

      One of the major issues on a mobile device is that a strong passphrase is extremely inconvenient since it needs to be entered so often. Strong passphrase + fingerprint works as a compromise but fingerprint / face / iris unlock is a gaping hole before it times out.

      1 reply 0 retweets 3 likes
    10. CopperheadOS‏ @CopperheadOS Apr 17
      Replying to @CopperheadOS @matthew_d_green and

      Don't just need to remember a strong passphrase but endlessly enter it over and over again which is a real pain especially without a real keyboard. It would be inconvenient even with a full size physical keyboard since devices lock so quickly (and for good reason).

      2 replies 0 retweets 2 likes
      Rich Felker‏ @RichFelker Apr 17
      Replying to @CopperheadOS @matthew_d_green and

      It's not just an inconvenience; it's a major security risk (shoulder surfing, etc.).

      12:13 PM - 17 Apr 2018
      1 reply 0 retweets 0 likes
        1. Rich Felker‏ @RichFelker Apr 17
          Replying to @RichFelker @CopperheadOS and

          Should only ask for strong pw for key derivation after manual secure-lock or any evidence of tampering/brute-force attempt. Detection of tampering should be 100% isolated from software control. Otherwise use user's preference of short pin or biometrics to unlock.

          0 replies 0 retweets 0 likes
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