Originally Posted By: tfabris
I wonder if the real heart of the issue here is that the "secure enclave" circuitry was mistakenly designed to place the retry-attempt-backoff-interval onus on the operating system rather than on the chip?

The secure enclave is not a factor with the iPhone 5c in the San Bernardino case. Only 64 bit iOS devices have the secure enclave portion of the SoC. The iPhone 5c was the last 32 bit iPhone Apple created. (Though the bitness of the CPU has nothing to do with the secure enclave, it's a convenient designation to know if it's there or not.)

So yes, for the iPhone 5c, only OS level software and the computational load limits retry attempts.

The 5s and above with the secure enclave may also be venerable to a method of bypassing delays somehow. It's unclear currently how in the discussion channels I've been following. The thought is that there is some sort of firmware upgrade path into the secure enclave that could be exploited.