Sunday, October 15, 2017

Cryptopals Set 3 -- F#

I've finished the remainder of Set 3 of the Cryptopals challenges... in the interest of time -- and of focusing on F# -- I've abandoned the parallel Python implementations for now.

The Mersenne Twister (MT) series were fairly interesting. Though the underlying math remains somewhat elusive, reading the pseudocode and implementing in F# gave me a good understanding of what happens in each iteration. One item that I didn't consider initially was the integer type. The 32-bit MT calls for an unsigned 32-bit integer... which should be fairly obvious, except that one rarely needs to think about different integer types in Python. A danger of starting with such a convenient language, perhaps...

I didn't properly break the fixed-nonce CTR (challenge 20), as my previous frequency analysis failed to fully decrypt to codes. But it looks like this will require revisiting in the next set of problems (challenge 25).

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