Wednesday, June 26, 2013

BASIC: Turing's Truth

Alan Turing showed that any finite-state machine can model any other.  That is how the team at Bletchley Park built the Bombe to imitate the German Enigma machine.  Today, we have “virtual machines” that let us put Unix and Windows on a Macintosh or Linux and Windows on a PC and so on.  The C language is actually an extension of itself, a realization by Kerninghan and Ritchie that inherent extensibility would allow programmers to create a language that would never become archaic.  And today we have C+, C++, and C#.  In fact, Ruby is just a set of macros written in C.  Once you have that, you can create your own Ruby objects, classes, and methods.  
 
Book cover shows silouette of man behind computer's punched card

The “Venture Rocket” blog presented a cute history of computer languages.  While one graphic did acknowledge Visual Basic as the seventh most popular development language, their history below that ignored Basic entirely. (They did cite Fortran and Cobol.) 

Earlier this month, I answered a challenge from the Praetorian computer security company to decipher this block of text.

Mpyza johsslunl ZWXY, Zluhabz Wvwbsbzxbl Yvthubz (Aol Zluhal huk Wlvwsl vm Yvtl), aolzl hyl aol budhclypun hsslnphujlz vm Aol Wyhlavyphu Nbhyk, luaybzalk if Jhlzhy av wyvcpkl aolpy lspal zljbypaf zlycpjlz huk luzbyl aol zhmlaf vm aol nsvihs Yvthu Ltwpyl. Hz aol zhfpun nvlz, "Hss Yvhkz Slhk av Yvtl", ovdlcly aol whao vm h Wyhlavyphu pz ulpaoly zayhpnoa uvy klalytpuhal. Aolyl hyl zlclyhs whaoz av qvpupun aol Wyhlavyphu Nbhyk, iba aol whao dlss-mvbuklk pu tlypa pz aol tvza ovuvyhisl. Pa pz mvy aopz ylhzvu aoha Jhlzhy ohz klcpzlk aopz zlyplz vm johsslunlz av qbknl aol tlypa vm wvaluaphs Wyhlavyphu yljybpaz. Fvb ohcl wyvclu fvbyzlsm ylzvbyjlmbs, iba kvu'a sla fvby nbhyk kvdu hz mhy tvyl kpmmpjbsa johsslunlz spl holhk. Av hjjlwa fvby ulea johsslunl, fvb dpss ullk av zluk tl h tlzzhnl vu Zrfwl. Av hkk tl hz h jvuahja, zluk h jvuahja ylxblza jvuahpupun aol alea "Zluhabz Wvwbsbzxbl Yvthubz" av "wyhlmljabz.jhzayvybt", aolu zluk tl h joha tlzzhnl av sla tl ruvd fvb'yl aolyl. Zll fvb vu aol ihaaslmplsk.

To do that, I wrote this program in BASIC.

10 REM Mike Marotta. June 21, 2013. Praetorian challenge.
11 REM: Claudic.bas compares cipher with known transposed key
12 REM: prints deciphered text
15 ON ERROR GOTO 199
20 P1$ = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
22 C1$ = "TUVWXYZABCDEFGHIJKLMNOPQRStuvwxyzabcdefghijklmnopqrs"
40 OPEN "i",1,"praeto.txt"
42 OPEN "o",2,"plain.txt"
50 LINE INPUT #1, X$
53 E = LEN(X$)
60 FOR I = 1 TO E
62 Q$ = MID$(X$,I,1)
63 REM Accept punctuation as is
64 IF ASC(Q$)<65 THEN PRINT#2,Q$;:
70 FOR J = 1 TO 52:
73 IF Q$=MID$(P1$,J,1) THEN PRINT#2, MID$(C1$,J,1);
80 NEXT J
85 NEXT I
90 GOTO 50
199 CLOSE 1: CLOSE 2
200 END

The program returned this decipherment.

First challenge SPQR, Senatus Populusque Romanus (The Senate and People of Rome), these are the unwavering allegiances of The Praetorian Guard, entrusted by Caesar to provide their elite security services and ensure the safety of the global Roman Empire. As the saying goes, "All Roads Lead to Rome", however the path of a Praetorian is neither straight nor determinate. There are several paths to joining the Praetorian Guard, but the path well-founded in merit is the most honorable. It is for this reason that Caesar has devised this series of challenges to judge the merit of potential Praetorian recruits. You have proven yourself resourceful, but don't let your guard down as far more difficult challenges lie ahead. To accept your next challenge, you will need to send me a message on Skype. To add me as a contact, send a contact request containing the text "Senatus Populusque Romanus" to "praefectus.castrorum", then send me a chat message to let me know you're there. See you on the battlefield.

Of course, this is merely a transliteration.  I already broke the cipher.  I found the common three-letter words, and guessed “the.”  I also guessed that the longest word would be “Praetorian” which then validated two of my letters in “the.”  All I wanted to do next was avoid the grunt work of writing out the answer. Computers are good for that.

Previously on Necessary Facts

2 comments:

  1. Well done Michael. Wishing you the best from your friends at Setec Astronomy.

    ReplyDelete
  2. Looks like Praetorian updated their online challenges. You may be interested in checking them out: http://www.praetorian.com/challenges/

    ReplyDelete