7
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Let's keep this movie train rolling! Below are a handful of Academy Award Best Picture winning movie titles, but each has been encrypted somehow. There is a common rule determining the encryption methods. Can you determine what each title is and how it was encrypted?

Titles

BUO QVRHT PW WHF FHSUNUN GARNU

PO CVWNTYA FOY QLD TGN

MJCTFWIG PO GTBKOC

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15
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BUO QVRHT PW WHF FHSUNUN GARNU decrypts as:

ALL QUIET ON THE WESTERN FRONT

PO CVWNTYA FOY QLD TGN decrypts as:

NO COUNTRY FOR OLD MEN

MJCTFWIG PO GTBKOC decrypts as:

LAWRENCE OF ARABIA

The encryption algorithm is:

Rotate all non-space letters by the year the movie was produced.
in: ALL QUIET ON THE WESTERN FRONT
salt: 193 01930 19 301 9301930 19301
out: BUO QVRHT PW WHF FHSUNUN GARNU

in: NO COUNTRY FOR OLD MEN
salt: 20 0720072 007 200 720
out: PO CVWNTYA FOY QLD TGN

in: LAWRENCE OF ARABIA
salt: 19621962 19 621962
out: MJCTFWIG PO GTBKOC

I'm sure there's a name for this kind of cypher. Someone can probably help me out with that.

I came to this conclusion by

first figuring out the names of the movies by the number of letters in each word. Once I had that, I ran a short little script that gave me the difference between each letter as a number.

def f(a, b):
  d = []
  for c in xrange(len(a)):
    if a[c] == ' ':
      continue
    d += [(ord(a[c])-ord(b[c])+26)%26]
  return d

The numbers that came back were sequences of the same four digits repeated over and over. I checked these digits against the release dates, and they matched.

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  • $\begingroup$ Fantastic, how did that salt occur to you? $\endgroup$ – Michael McGriff Sep 11 '15 at 19:17
  • $\begingroup$ Well, [redacted]. Added within the answer so it can be hidden. $\endgroup$ – Ian MacDonald Sep 11 '15 at 19:34
  • $\begingroup$ Thinking its something related to a Vigenaire-Chiffre $\endgroup$ – masterX244 Sep 11 '15 at 19:49
  • $\begingroup$ Nicely done Ian! Solved singlehandedly. Well deserved $\endgroup$ – NeedAName Sep 11 '15 at 20:12
  • 1
    $\begingroup$ This particular version is the Gronsfeld cipher. $\endgroup$ – f'' Sep 11 '15 at 22:48

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