Lecture 25

CX 103: Introduction to Computers

Lecture 26

Handouts
Encryption.html
Computer Dating Questionnaire
Light Bulb Jokes/Computer Dating

Today's Agenda

Drop-Down Menus

Computer Dating

The Encryption Program

Cryptology and Computer Security

HTML/JavaScript Trick of the Day

Drop Down Menus

Minilightbulbs.html

<HTML>

<HEAD>

<TITLE>Light Bulb Jokes</TITLE>

var A = new Array(5);

A[1] = "Five--one to change the light bulb and four to find the perfect J. Crew outfit to wear for the occasion";

A[2] = "One--he holds the bulb and the world revolves around him.";

A[3] = "None--Hanover does not have electricity." ;

A[4] = "Thirteen--one to change the bulb and an a capella group to immortalize the event in song.";

function Begin()

{ var index, response;

index = document.MyForm.College.selectedIndex;

response = document.MyForm.College.options[index].value;

document.MyForm.Answer.value = A[response];

}

</SCRIPT>

</HEAD>

<H2>How many students at your favorite college does it take to change a light bulb?

<H3>Select a College:

<OPTION VALUE = "1" SELECTED >Middlebury

<OPTION VALUE = "2">Harvard

<OPTION VALUE = "3">Dartmouth

<OPTION VALUE = "4">Amherst

</SELECT>

<P>

Answer:<BR>

</P>

<INPUT TYPE = "button" VALUE = "Click for Answer" SIZE = "20"

ONCLICK = "Begin()" >

</FORM>

</BODY>

</HTML>

LightBulbs.html

CX 103 Computer Dating Questionnaire

Name

Answer Each of the following Questions with a "YES" or a "NO"

You may check the appropriate box:

Question Yes No

Do you prefer raw carrots to cooked carrots?

Do you prefer black jelly beans to other colors?

Do you like Burger King more than McDonald's?

Do you prefer to squeeze toothpaste from the bottom of the tube?

Do you like the morning more than the evening?

Do you prefer cats to dogs?

Do you prefer the Red Sox to the Yankees?

Do you prefer jazz to opera?

Do you prefer pickup trucks to SUV's?

Do you enjoy sleeping with the window open?

Multiple-Subscripted Arrays

Arrays and Computer Dating Services

	#1	#2	#3	#4	#5	#6	#7	#8	#9	#10
Andrew	Yes	No	No	Yes	Yes	Yes	Yes	No	No	No
Annalise	Yes	Yes	Yes	No	No	Yes	No	No	Yes	Yes
Beth	Yes	Yes	No	No	Yes	No	Yes	Yes	Yes	Yes
Bob	No	Yes	Yes	Yes	No	No	No	Yes	No	No
Brendan	Yes	No	Yes	Yes	Yes	No	No	Yes	Yes	Yes
Casey	Yes	No	Yes	Yes	No	Yes	Yes	No	Yes	Yes
Charles M	Yes	No	No	Yes	Yes	No	Yes	Yes	No	Yes
Charles R	No	Yes	No	Yes	Yes	No	No	Yes	No	No
Colin	Yes	Yes	Yes	No	No	No	Yes	Yes	Yes	Yes
David M	Yes	No	Yes	Yes	No	Yes	No	Yes	Yes	No
David R	No	No	No	No	No	Yes	Yes	Yes	Yes	No
David S	Yes	No	No	Yes	No	Yes	No	No	No	Yes
Eliza	Yes	Yes	No	Yes	Yes	No	No	Yes	Yes	Yes
John	No	Yes	No	Yes	Yes	No	Yes	No	No	Yes
Jordan	Yes	Yes	No	Yes	Yes	No	Yes	No	Yes	No
Kate	Yes	No	No	No	No	No	Yes	Yes	No	Yes
Kennan	Yes	Yes	No	No	No	No	No	Yes	No	Yes
Liz	No	Yes	No	Yes	Yes	No	No	No	Yes	Yes
Louisa	Yes	No	No	Yes	No	No	Yes	Yes	No	No
Matt	No	Yes	No	No	Yes	Yes	No	Yes	Yes	No
Megan	Yes	No	No	Yes	Yes	Yes	Yes	No	Yes	No
Missy	No	No	No	Yes	No	No	No	Yes	No	No
Nathaniel	Yes	No	No	No	Yes	No	No	Yes	No	Yes
Rada	No	No	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes
Rebecca	No	Yes	No	Yes	No	No	No	Yes	No	Yes
Ryan B	Yes	No	Yes	Yes	Yes	Yes	No	No	Yes	No
Ryan P	Yes	Yes	No	No	Yes	No	No	No	Yes	Yes
Ted	Yes	No	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes
Tejas	Yes	No	Yes	Yes	No	No	Yes	Yes	Yes	No
Trevor	No	Yes	No	Yes	No	Yes	Yes	No	No	Yes
Tyler	No	Yes	No	No	No	No	Yes	Yes	Yes	No
Veljko	No	Yes	Yes	Yes	No	No	Yes	No	No	Yes

Consider an array with 33 elements with elements 1 through 32 corresponding to the individual students in the class. The element in cell 0 is the instructor, but his answers to the questions are not known.

Each element Student[i] is itself an array with 12 cells. In cell 0 is the student's name. In cells 1 - 10 are the "Yes" or "No" answers to each question.

Cell 11 is reserved for saving the number of matches with some other prescribed student

Rebecca No Yes No Yes No No No Yes No Yes

David S Yes No No Yes No Yes No No No Yes 6

Rebecca No Yes No Yes No No No Yes No Yes

Tyler No Yes No No No No Yes Yes Yes No 6

Rebecca No Yes No Yes No No No Yes No Yes

Veljko No Yes Yes Yes No No Yes No No Yes 7

<HTML>

<HEAD> <TITLE>Computer Dating </TITLE>

<SCRIPT LANGUAGE = "JavaScript" >;

var Student = new Array(5);

for (i = 0; i <= 32; i = i + 1)

Student[i] = new Array(12);

Student[1] = ["Andrew", "Yes", "No", "No", "Yes", "Yes", "Yes", "Yes", "No", "No", "No",0];

Student[2] = ["Annalise", "Yes", "Yes", "Yes", "No", "No", "Yes", "No", "No", "Yes", "Yes",0];

Student[3] = ["Beth", "Yes", "Yes", "No", "No", "Yes", "No", "Yes", "Yes", "Yes", "Yes",0];

Student[4] = ["Bob", "No", "Yes", "Yes", "Yes", "No", "No", "No", "Yes", "No", "No",0];

Student[5] = ["Brendan", "Yes", "No", "Yes", "Yes", "Yes", "No", "No", "Yes", "Yes", "Yes",0];

Student[6] = ["Casey", "Yes", "No", "Yes", "Yes", "No", "Yes", "Yes", "No", "Yes", "Yes",0];

Student[7] = ["CharlesM", "Yes", "No", "No", "Yes", "Yes", "No", "Yes", "Yes", "No", "Yes",0];

Student[8] = ["CharlesR", "No", "Yes", "No", "Yes", "Yes", "No", "No", "Yes", "No", "No",0];

Student[9] = ["Colin", "Yes", "Yes", "Yes", "No", "No", "No", "Yes", "Yes", "Yes", "Yes",0];

Student[10] = ["DavidM", "Yes", "No", "Yes", "Yes", "No", "Yes", "No", "Yes", "Yes", "No",0];

Student[11] = ["DavidR", "No", "No", "No", "No", "No", "Yes", "Yes", "Yes", "Yes", "No",0];

Student[12] = ["DavidS", "Yes", "No", "No", "Yes", "No", "Yes", "No", "No", "No", "Yes",0];

Student[13] = ["Eliza", "Yes", "Yes", "No", "Yes", "Yes", "No", "No", "Yes", "Yes", "Yes",0];

Student[14] = ["John", "No", "Yes", "No", "Yes", "Yes", "No", "Yes", "No", "No", "Yes",0];

Student[15] = ["Jordan", "Yes", "Yes", "No", "Yes", "Yes", "No", "Yes", "No", "Yes", "No",0];

Student[16] = ["Kate", "Yes", "No", "No", "No", "No", "No", "Yes", "Yes", "No", "Yes",0];

Student[17] = ["Kennan", "Yes", "Yes", "No", "No", "No", "No", "No", "Yes", "No", "Yes",0];

Student[18] = ["Liz", "No", "Yes", "No", "Yes", "Yes", "No", "No", "No", "Yes", "Yes",0];

Student[19] = ["Louisa", "Yes", "No", "No", "Yes", "No", "No", "Yes", "Yes", "No", "No",0];

Student[20] = ["Matt", "No", "Yes", "No", "No", "Yes", "Yes", "No", "Yes", "Yes", "No",0];

Student[21] = ["Megan", "Yes", "No", "No", "Yes", "Yes", "Yes", "Yes", "No", "Yes", "No",0];

Student[22] = ["Missy", "No", "No", "No", "Yes", "No", "No", "No", "Yes", "No", "No",0];

Student[23] = ["Nathaniel", "Yes", "No", "No", "No", "Yes", "No", "No", "Yes", "No", "Yes",0];

Student[24] = ["Rada", "No", "No", "Yes", "Yes", "Yes", "No", "Yes", "Yes", "Yes", "Yes",0];

Student[25] = ["Rebecca", "No", "Yes", "No", "Yes", "No", "No", "No", "Yes", "No", "Yes",0];

Student[26] = ["RyanB", "Yes", "No", "Yes", "Yes", "Yes", "Yes", "No", "No", "Yes", "No",0];

Student[27] = ["RyanP", "Yes", "Yes", "No", "No", "Yes", "No", "No", "No", "Yes", "Yes",0];

Student[28] = ["Ted", "Yes", "No", "Yes", "Yes", "No", "Yes", "Yes", "Yes", "Yes", "Yes",0];

Student[29] = ["Tejas", "Yes", "No", "Yes", "Yes", "No", "No", "Yes", "Yes", "Yes", "No",0];

Student[30] = ["Trevor", "No", "Yes", "No", "Yes", "No", "Yes", "Yes", "No", "No", "Yes",0];

Student[31] = ["Tyler", "No", "Yes", "No", "No", "No", "No", "Yes", "Yes", "Yes", "No",0];

Student[32] = ["Veljko", "No", "Yes", "Yes", "Yes", "No", "No", "Yes", "No", "No", "Yes",0];

client1 = parseInt(window.prompt("Enter number of first client","") );

client2 = parseInt(window.prompt("Enter number of second client","") );

document.writeln("<H2>");

Matches = 0;

for (j = 0; j <= 10; j = j + 1)

{ document.writeln( Student[client1][j] + " <FONT COLOR = red > " + Student[client2][j] +"</FONT><BR>");

if ( Student[client1][j] == Student[client2][j] ) Matches = Matches + 1

}

document.writeln("<BR>" + "Number of matches " + Matches);

</SCRIPT>

</HEAD> <BODY BGCOLOR = "linen"); </BODY> </HTML>

Dating.html

ENCRYPTION ASSIGNMENT

Encryption.html

Original:

Break message into pairs of consecutive characters.

Replace each pair by 4 digit number made up of their ASCII values

Add 7 % 10 to each digit.

Reverse the digits.

1. <HTML>

2. <HEAD>

3. <TITLE>Stage One of Encryption</TITLE>

4. <SCRIPT LANGUAGE = "Javascript">

5.

6. var W, i, S;

7.

8.

9. function Begin()

10. { var i, A,B,S, T, Number, Length, M, First, Second, Third, Fourth;

11. W = document.EncryptForm.Phrase.value;

12.

13. Length = W.length;

14.

15. S = "It has " + Length + " characters.";

16. Append = "That is an odd number. I will append an X to the end and
proceed with the encryption."

17.

18.

19.

20. if (W.length % 2 == 1)

21. { S = S + Append;

22. W = W + "X";

23. Length = Length + 1 }

24.

25. var Originals = new Array(Length/2);

26.

27. document.EncryptForm.Comment.value = S;

28.

29. T = "Its original numerical representation is ";

30. document.EncryptForm.Digits.value = T;

31.

32. for (i = 0; i < Length ; i = i + 2)

33. { A = W.charCodeAt(i) ;

34. B = W.charCodeAt(i+1) ;

35. Number = 100*A + B;

36. Originals[i/2] = Number;

37. }

38.

39. document.EncryptForm.plain.value = Originals.join(" ");;

40.

41. var Scrambleds = new Array (Length/2);

42. var Digits = new Array(4)

43.

44. function power(k)

45. { var i, N;

46. N = 1;

47. for (i = 1; i <= k; i = i+ 1) N = N * 10;

48. return N;

49. }

50.

51. for (i = 0; i < Length/2; i = i + 1)

52. {

53. M = Originals[i];

54. for (j = 0; j <= 3; j = j+ 1)

55. { Digits[j] = Math.floor(M/power(j));

56. Digits[j] = ( Digits[j] + 7) % 10; }

57. M = 0;

58. for (j = 0; j <= 3; j = j+ 1)

59. M = M + Digits[j] * power(3-j);

60.

61.

62. Scrambleds[i] = M

63. }

64.

65. document.EncryptForm.Scrambled.value = Scrambleds.join(" ");

66.

67.

68. }

69.

70.

71. </SCRIPT>

72. </HEAD>

73. <BODY BGCOLOR = "white">

74. <FORM NAME = "EncryptForm">

75. Enter a word or phrase <INPUT NAME = "Phrase" SIZE = 80 TYPE = "text">

76. <BR>

77. <INPUT TYPE = "button" VALUE = "Click to Encrypt" SIZE = "20"

78. ONCLICK = "Begin()" >

79. <BR>

80. <TEXTAREA NAME = "Comment" ROWS =4 COLS = 50 TYPE =
"text"> </TEXTAREA>

81. <BR>

82. <INPUT NAME = "Digits" SIZE = 50 TYPE = "text">

83. <BR>

84. <TEXTAREA NAME = "plain" ROWS = 5 COLS = 50 TYPE = "text"> </TEXTAREA>

85. <BR>

86. <H2>The encrypted message is:

87. <BR>

88. <TEXTAREA NAME = "Scrambled" ROWS = 5 COLS = 50
TYPE = "text">

89. </TEXTAREA>

90. </FORM>

91. </BODY>

92. </HTML>

How secure is this method?

How can we make it more secure?

(1) Use a different number other than 7 to add mod 10. Keep that digit secret.

(2) Try some other rearrangment of the digits. (also secret)

How many possibilities are there?

( 10 numbers ) * (4! = 24 rearrangements) = 240

Could we "crack" a secret message by brute force?

(3) Use a different number to add to each digit

Example: Add 2 % 10 to First Digit

Add 9 % 10 to Second Digit

Add 5 % 10 to Third Digit

Add 7 % 10 to Fourth Digit

How many possibilites are there now?

10 * 10 * 10 * 10 * 4! = 240, 000

(4) Use triples of characters to make up six digit numbers.

How many possibilites are there now?

( 10 * 10 * 10 * 10 * 10 * 10) * 6! = 720,000,000

We are a little ahead of the game.

For now, let's continue to add 7 % 10 to each digit and reverse the digits when we are done, but we'll work with 6 digit numbers instead of 4 digit numbers:

Example:

MIDDLEBURY_COLLEGE

Triple ASCII + 7 % 10 Reverse

MID 777368 444035 530444

DLE 687669 354336 633453

BUR 668582

Y_C 893267

OLL 797676

EGE 697160

M I D D L E B U R Y C O L L E G E

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

77 73 68 68 76 69 66 85 82 89 32 67 79 76 76 69 71 69

Programming Issues:

(1)

W is "plaintext" character string

Length of W is W.length

If W.length is not a multiple of 3, we need to pad on extra X's at the end.

How many X's ?

W.length % 3 Number of X's

0 0

1 2

2 1

Extensions: If we plan to break up message into blocks of k letters, then length must be a multiple of k.

Example: k = 6

W.length % 6 Number of X's

0 0

1 5 6 - 1

2 4 6 - 2

3 3 6 - 3

4 2 6 - 4

5 1 6 - 5

Issue (2): Getting the six digit number

32. for (i = 0; i < Length ; i = i + 2)

33. { A = W.charCodeAt(i) ;

34. B = W.charCodeAt(i+1) ;

35. Number = 100*A + B;

36. Originals[i/2] = Number;

for (i = 0; i < Length ; i = i + 3)

{ A = W.charCodeAt(i) ;

B = W.charCodeAt(i+1);

C = W.charCodeAt(i+2);

Number = 10000*A + 100*B+ C;

Originals[i/3] = Number; }

Questions:

What if we use blocks of 6 consecutive characters?

k consecutive characters where k is specified by user when program runs?

Issue (3) Getting the individual digits:

51. for (i = 0; i < Length/2; i = i + 1)

52. {

53. M = Originals[i];

54. for (j = 0; j <= 3; j = j+ 1)

55. { Digits[j] = Math.floor(M/power(j));

56. Digits[j] = ( Digits[j] + 7) % 10; }

57. M = 0;

58. for (j = 0; j <= 3; j = j+ 1)

59. M = M + Digits[j] * power(3-j);

Issue (4) reporting the results:

41. var Scrambleds = new Array (Length/2);

62. Scrambleds[i] = M

63. }

64.

65. document.EncryptForm.Scrambled.value = Scrambleds.join(" ");

86. <H2>The encrypted message is:

87. <BR>

88. <TEXTAREA NAME = "Scrambled" ROWS = 5 COLS = 50
TYPE = "text">

The Output

65. document.EncryptForm.Scrambled.value = Scrambleds.join(" ");

produces

530444 633453 952533 439065 343464 638463 50490 546490 649063 159074 906394 56333 349015 633304 342395 952390 900515 346443 846334 900563 905404 639415 312590 553105

while

document.EncryptForm.Scrambled.value = Scrambleds.join("")

produces;

5304446334539525334390653434646384635049054649064906315907490639456333349015633304342395952390900515346443846334900563905404639415312590553105

We'll be back after this brief message:

Programmers on a Highway

Two computer programmers are driving on a Highway. They switch on the radio and there is a warning: Please note that a car is driving on highway 75 against the traffic. The programmer near the driver looks at him and says: One? There are hundreds of them.

Cryptology and Computer Security

Why Should You Be Interested in Cryptology?

Historical Importance

Military

Diplomatic

Contemporary Importance

Data Protection

Secure Communications

Vehicle to Study Mathematical Topics

Number Theory	Linear Algebra
Discrete Mathematics	Computers
Probability and Statistics

Intellectual Stimulation

Many Open Research Questions

Links to Other Disciplines

Engineering Linguistics

CRYPTOLOGY

CRYPTOGRAPHY	*CRYPTANALYSIS*
Hiding the meaning of messages	Discovering the meaning of intercepted messages

CRYPTOGRAPHY

A) HIDING THE EXISTENCE OF A MESSAGE

Steganography

Invisible Ink

Microdots

Pinholes

B) HIDING THE MEANING OF A MESSAGE

Transpositions

Substitutitons

SUBSTITUTIONS

CODES

CIPHERS

CODES

plaintext ATTACK AT DAWN

coded text 15921 24586 49198

CIPHERS

Example: Replace each letter by the next one in the alphabet

plaintext ATTACK AT DAWN

ciphertext BUUBDL BU EBXO

CIPHERS

MONALPHABETIC SUBSTITUTION

POLYALPHABETIC SUBSTITUTION

POLYGRAPHIC SYSTEMS

MONALPHABETIC SUBSTITUTION

Caesar Cipher: Replace each letter of the message by the letter 3 places beyond it in the normal alphabet.

plaintext A B C D E F G H I J K L M

ciphertext D E F G H I J K L M N O P

plaintext N O P Q R S T U V W X Y Z

ciphertext Q R S T U V W X Y Z A B C

AT T ACK AT DAWN

DWWDFN DW GD ZQ

Numerical Implementation

of Caesar Cipher

1) Replace each letter by its position in the alphabet

2) Add 3 % 26 to the position

3) Replace resulting number by its letter equivalent

M --> 13 --> 16 --> P

In JavaScript

Phrase is variable name; it contains a character string.

The first character in Phrase is Phrase.charAt(0);

Its ASCII value is ascii = Phrase.charCodeAt(0);

Its position in the alphabet is position = ascii - 64

To add 3 mod 26: cipherPosition =(position + 3) % 26

Now cipherPosition is the position of new letter in the alphabet.

Its ASCII value is x = cipherPosition + 64.

The corresponding letter is String.fromCharCode(x)

Summarizing:

ascii = Phrase.CharCodeAt(0);

position = ascii - 64;

cipherPosition =(position + 3) % 26

NewAscii = cipherPosition + 64

CipherCharacter = String.fromCharCode(NewAscii)

Caesar.html

Another View Of The Substiution Table

PlainText
Character
CipherText
Character
PlainText
Character
CipherText
Character

A D N Q

B E O R

C F P S

D G Q T

E H R U

F I S V

G J T W

H K U X

I L V Y

J M W Z

K N X A

L O Y B

M P Z C

Note that the red letters are just a rearrangement of the blue letters.

Any rearrangement of the alphabet produces another substitutiton scheme.

Here is another way to get a rearrangement;

Pick a key word: VERMONT

Make the letters the heads of columns in a table.

Fill in the rest of the alphabet into the table from left to right.

V E R M O N T

A B C D F G H

I J K L P Q S

U W X Y Z

Then read the letters out of the table, column by column

going from left to right, reading each column from top to bottom:

VAIU EBJW RCKX MDLY OFPZ NGQ THS

This will be our arranged alphabet:

VAIUEBJWRCKXMDLYOFPZNGQTHS

The New Substiution Table

PlainText
Character
CipherText
Character
PlainText
Character
CipherText
Character

A V N D

B A O L

C I P Y

D U Q O

E E R F

F B S P

G J T Z

H W U N

I R V G

J C W Q

K K X T

L X Y H

M M Z S

How Many Rearrangements of the Alphabet are There?

26 * 25 * 24 * ... * 3 * 2 * 1 = 26!

26! is about 4 followed by 26 0's

We can use any of these monoalphabetic substitutions to encipher a message.

Suppose we intercept a message that was enciphered by using one of these schemes.

We try to "crack the code" by checking every possible scheme.

Would this work in theory?

Would in work in practice?

Suppose we could check 1,000,000 per second.

How long would it take to check them all?

Question	Yes	No
Do you prefer raw carrots to cooked carrots?
Do you prefer black jelly beans to other colors?
Do you like Burger King more than McDonald's?
Do you prefer to squeeze toothpaste from the bottom of the tube?
Do you like the morning more than the evening?
Do you prefer cats to dogs?
Do you prefer the Red Sox to the Yankees?
Do you prefer jazz to opera?
Do you prefer pickup trucks to SUV's?
Do you enjoy sleeping with the window open?

1.	<HTML>
2.	<HEAD>
3.	<TITLE>Stage One of Encryption</TITLE>
4.	<SCRIPT LANGUAGE = "Javascript">
5.
6.	var W, i, S;
7.
8.
9.	function Begin()
10.	{ var i, A,B,S, T, Number, Length, M, First, Second, Third, Fourth;
11.	W = document.EncryptForm.Phrase.value;
12.
13.	Length = W.length;
14.
15.	S = "It has " + Length + " characters.";
16.	Append = "That is an odd number. I will append an X to the end and proceed with the encryption."
17.
18.
19.
20.	if (W.length % 2 == 1)
21.	{ S = S + Append;
22.	W = W + "X";
23.	Length = Length + 1 }
24.
25.	var Originals = new Array(Length/2);
26.
27.	document.EncryptForm.Comment.value = S;
28.
29.	T = "Its original numerical representation is ";
30.	document.EncryptForm.Digits.value = T;
31.
32.	for (i = 0; i < Length ; i = i + 2)
33.	{ A = W.charCodeAt(i) ;
34.	B = W.charCodeAt(i+1) ;
35.	Number = 100*A + B;
36.	Originals[i/2] = Number;
37.	}
38.
39.	document.EncryptForm.plain.value = Originals.join(" ");;
40.
41.	var Scrambleds = new Array (Length/2);
42.	var Digits = new Array(4)
43.
44.	function power(k)
45.	{ var i, N;
46.	N = 1;
47.	for (i = 1; i <= k; i = i+ 1) N = N * 10;
48.	return N;
49.	}
50.
51.	for (i = 0; i < Length/2; i = i + 1)
52.	{
53.	M = Originals[i];
54.	for (j = 0; j <= 3; j = j+ 1)
55.	{ Digits[j] = Math.floor(M/power(j));
56.	Digits[j] = ( Digits[j] + 7) % 10; }
57.	M = 0;
58.	for (j = 0; j <= 3; j = j+ 1)
59.	M = M + Digits[j] * power(3-j);
60.
61.
62.	Scrambleds[i] = M
63.	}
64.
65.	document.EncryptForm.Scrambled.value = Scrambleds.join(" ");
66.
67.
68.	}
69.
70.
71.	</SCRIPT>
72.	</HEAD>
73.	<BODY BGCOLOR = "white">
74.	<FORM NAME = "EncryptForm">
75.	Enter a word or phrase <INPUT NAME = "Phrase" SIZE = 80 TYPE = "text">
76.	<BR>
77.	<INPUT TYPE = "button" VALUE = "Click to Encrypt" SIZE = "20"
78.	ONCLICK = "Begin()" >
79.	<BR>
80.	<TEXTAREA NAME = "Comment" ROWS =4 COLS = 50 TYPE = "text"> </TEXTAREA>
81.	<BR>
82.	<INPUT NAME = "Digits" SIZE = 50 TYPE = "text">
83.	<BR>
84.	<TEXTAREA NAME = "plain" ROWS = 5 COLS = 50 TYPE = "text"> </TEXTAREA>
85.	<BR>
86.	<H2>The encrypted message is:
87.	<BR>
88.	<TEXTAREA NAME = "Scrambled" ROWS = 5 COLS = 50 TYPE = "text">
89.	</TEXTAREA>
90.	</FORM>
91.	</BODY>
92.	</HTML>

Triple	ASCII	+ 7 % 10	Reverse
MID	777368	444035	530444
DLE	687669	354336	633453
BUR	668582
Y_C	893267
OLL	797676
EGE	697160

M	I	D	D	L	E	B	U	R	Y		C	O	L	L	E	G	E
0	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17
77	73	68	68	76	69	66	85	82	89	32	67	79	76	76	69	71	69

W.length % 6	Number of X's
0	0
1	5	6 - 1
2	4	6 - 2
3	3	6 - 3
4	2	6 - 4
5	1	6 - 5

plaintext	ATTACK AT DAWN
coded text	15921 24586 49198

plaintext	ATTACK AT DAWN
ciphertext	BUUBDL BU EBXO

PlainText Character	*CipherText* *Character*	PlainText Character	*CipherText* *Character*
A	D	N	Q
B	E	O	R
C	F	P	S
D	G	Q	T
E	H	R	U
F	I	S	V
G	J	T	W
H	K	U	X
I	L	V	Y
J	M	W	Z
K	N	X	A
L	O	Y	B
M	P	Z	C

M	I	D	D	L	E	B	U	R	Y		C	O	L	L	E	G	E
0	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17
77	73	68	68	76	69	66	85	82	89	32	67	79	76	76	69	71	69

M	I	D	D	L	E	B	U	R	Y		C	O	L	L	E	G	E
0	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17
77	73	68	68	76	69	66	85	82	89	32	67	79	76	76	69	71	69