Friday, September 20, 2013

Sections 2.9-2.11, due September 20

1. For the LFSR, and for other cryptosystems we've learned about, it seems like there's a certain amount of educated guessing. For the LFSR, it's guessing the length of the recurrence. Is there a systematic way to guessing what the length of the recurrence is, or should I just start from 1 and work my way up?

2. My first thought was "Blum-Blum-Shub? Who names anything, let alone a pseudo-random bit generator, something like "Blum-Blum-Shub?" Anyway, I had never heard of a linear feedback shift register, so I found it really interesting. The use of binary is easier and harder to understand in some ways than using letters. For example, I'm glad to be working with mod 2 now instead of mod 26, but these ciphers are more difficult to decrypt because of the limited characters that could be repeating.

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