Finding the IC of a sample text

by fortenforge, Nov 3, 2009, 11:34 PM

Let's find the IC of the plaintext "THE PATIENT REFUSED AN AUTOPSY"

A 3
B 0
C 0
D 1
E 4
F 1
G 0
H 1
I 1
J 0
K 0
L 0
M 0
N 2
O 1
P 2
Q 0
R 1
S 2
T 4
U 2
V 0
W 0
X 0
Y 1
Z 0

Now we plug this into the formula we derived earlier.
I excluded any 1's and 0's because they would just become 0.
$(3\cdot2 + 4 \cdot 3 + 2 \cdot 1 + 2 \cdot 1 + 2 \cdot 1 + 4 \cdot 3 + 2 \cdot 1)/(26 \cdot 25)$ .
$= \frac {38}{26\cdot25} = \boxed{0.0584615385}$ .

Index of Coincidence

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Good website!
by bluegoose101, Aug 5, 2021, 6:28 PM
uh-huh, a great place here
by fenchelfen, Sep 1, 2019, 11:30 AM
uh, yeah he is o_O
by SonyWii, Oct 8, 2010, 2:11 PM
dude i think you're my roommate from camp :O
by themorninglighttt, Aug 29, 2010, 10:06 PM
what i'm still not a contrib D:
by SonyWii, Aug 6, 2010, 2:20 PM
I see what you did there
by Jongy, Aug 1, 2010, 11:52 PM
omg, apparently you like cryptography; and apparently I'm not a contribb D:
by SonyWii, Jul 26, 2010, 9:48 PM
Thank You
by fortenforge, Jan 17, 2010, 6:35 PM
Wow this is a really cool blog
by alkjash, Jan 16, 2010, 7:04 PM
Hi
by fortenforge, Jan 7, 2010, 12:12 AM
Hi
by Richard_Min, Jan 5, 2010, 9:29 PM
Hi
by fortenforge, Jan 3, 2010, 10:14 PM
HELLO FORTENFORGE I AM THE PERSON SITTING NEXT TO YOU IN IDEAMATH
by ButteredButNotEaten, Dec 24, 2009, 4:19 AM
@dragon96 Not if you celebrate Christmas with neon lights
@batteredbutnotdefeated Sure, You are now a contributer
by fortenforge, Dec 20, 2009, 4:39 AM
I too share a love for cryptography and cryptanalysis, may I be a contrib?
by batteredbutnotdefeated, Dec 20, 2009, 2:38 AM
The green is too bright for Christmas.
by dragon96, Dec 20, 2009, 2:12 AM
I thought I'd change the colors for the Holidays
by fortenforge, Dec 13, 2009, 10:53 PM
hi, some "simple" cryptography here: http://www.artofproblemsolving.com/Forum/weblog_entry.php?t=317795
by phiReKaLk6781, Dec 12, 2009, 3:46 AM
Yeah, that is binary, for modern cryptography, most text is converted to binary first and then algorithm's for encryption are preformed on the binary rather than the English letters. The text is converted using the ASCII table or UNICODE.
by fortenforge, Oct 13, 2009, 10:33 PM
Whoa, I love your background! Is that binary?
by pianogirl, Oct 13, 2009, 8:34 PM
Sure, I'll add you as a contributer...
by fortenforge, Oct 2, 2009, 4:44 AM
May I make a post on one cipher I made up? (It's a good code for science people! *hint hint*)
by dragon96, Oct 2, 2009, 4:04 AM
Nice blog, this is interesting...

and guess who i am
by Yoshi, Sep 21, 2009, 4:02 AM
Thanks
by fortenforge, Sep 17, 2009, 1:33 AM
Very interesting blog. Nice!
by AIME15, Sep 16, 2009, 5:21 PM
When you mean 'write' do you mean like programming? Much of cryptography has to do with programming and most modern cryptographers are excellent programmers because modern complex ciphers are difficult to implement by hand.

See if you can write a program for the substitution cipher. The user should be able to enter the key and the message. I know it is possible to do it in pretty much any language because I was able to do it in c.
by fortenforge, Aug 7, 2009, 8:17 PM
Hello. I don't know much about advanced cryptography but I did write a Caeser Chipher encrypter and decrypter!
by Poincare, Jul 31, 2009, 8:55 PM

27 shouts

Cryptography

Finding the IC of a sample text

by fortenforge, Nov 3, 2009, 11:34 PM

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