How can we get rid of the tell tale fingerprints of the charactertistics frequencies?

POLYALPHABETIC SUBSTITUTION

Vigenere Cipher




Idea: Use different shifts for different characters in the message: The amount you shift depends on the relative position of the character in the message
 
 
 
 

keyword: VERMONT
 
V E R M O N T V E R M O N T V E R  
M I D D L E B U R Y C O L L E G E  

SECURITY OF VIGENERE CIPHER

"Le Chiffre Indechiffrable"

Basis of German Enigma Machine


 


Vigenere Cipher cracked by

Charles Babage (1854)

Friedrich W. Kasiski (1805 - 1881) (1863)
 
 
 

How to crack a Vigenere Cipher:

Determine length of keyword

Use frequency analysis on subsets of the cipher text consisting of text enciphered with the same shift.


 

Kasiski Method

Our Cryptogram

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
 
 


Frequency Distribution of Individual Letters


 
A 70   G 116   L 131   Q 89   V 101
B 82   H 148   M 86   R 83   W 129
C 85   I 110   N 110   S 100   X 134
D 128   J 127   O 51   T 113   Y 114
E 76   K 90   P 67   U 128   Z 93
F 131                        

 

Some Repeated Strings

FEXUXPQI

Location Location Gap Factors
96 1743 1647 3*3*3*61
1743 1797 54 3*3*3*2
1797 2544 747 3*3*83

NCZLNUTQ


 
Location Location Gap Factors
704 1001 297 3*3*3*11
1001 1388 387 3*3*43
1388 2063 675 3*3*3*5*5

DBRHDWFF


 
Location Location Gap Factors
144 900 756 3*3*3*2*2*7

 

STEKQCFF


 
Location Location Gap Factors
855 2457 1602 3*3*2*89

 

Our Conclusion:
 
 

Keyword must have 9 letters
 
 


Test our hypothesis:

Break Message up by taking every 9th letter starting from the first and put them in one pile.

Then take every 9th letter starting from the second and put them in a pile.

etc.

Do a frequency analysis of each pile.

They should match the frequency distribution of standard English shifted by some amount.

Characters Counted in each column: 299
 
Col. 1 2 3 4 5 6 7 8 9
A 0 11 17 2 6 1 5 16 12
B 1 11 17 16 2 10 4 0 20
C 0 27 11 10 10 25 0 2 0
D 27 25 0 23 37 0 1 13 2
E 4 7 19 21 0 3 0 9 13
F 12 2 26 11 0 12 34 26 8
G 12 22 22 0 10 6 5 22 17
H 33 11 12 15 5 24 11 9 28
I 10 24 4 19 18 18 11 0 6
J 7 5 5 30 23 10 33 14 0
K 15 2 0 13 9 1 9 14 27
L 26 4 2 4 1 38 3 31 22
M 0 0 0 1 22 16 10 8 29
N 2 5 33 0 18 12 29 3 8
O 10 0 4 1 20 10 0 3 3
P 10 20 20 0 8 4 2 0 3
Q 24 2 11 29 8 2 8 5 0
R 17 10 35 2 5 0 8 0 6
S 8 13 9 10 0 2 30 28 0
T 0 41 9 8 6 0 19 4 26
U 22 2 12 36 0 31 10 12 3
V 18 6 20 7 26 4 0 13 7
W 26 12 0 9 2 17 13 38 12
X 6 37 2 19 7 9 18 4 32
Y 4 0 6 13 9 35 28 10 9
Z 5 0 3 0 47 9 8 15 6
                   
                   
                   
                   
E? 8 20 18 21 26 25 10 23 24
Shift 3 15 13 16 21 20 5 18 19
  C O M P U T E R S

 
 
 

THEUNITEDSTATESHASSUSPENDEDITSAERIALDRUGINTERCEPTIONPROGRAMOVERCOLOMBIASINCETHEMISTAKENATTACKONAAMERICANMISSIONARYPLANEFLYINGOVERPERUONFRIDAYTHEAMERICANSTATEDEPARTMENTSAIDONWEDNESDAYTHEUNITEDSTATESUSPENDEDTHEAERIALSURVEILLANCEPROGRAMOVERPERULASTWEEKAFTERAPERUVIANAIRFORCEPLANESHOTATTHEMISSIONARIESINTHEIRSMALLPLANEOVEREASTERNPERUKILLINGANAMERICANWOMANANDHERCHILDTHEINTERCEPTPROGRAMHASBEENSUSPENDEDALSOINCOLOMBIASTATEDEPARTMENTSPOKESMANPHILIPREEKERTOLDHISDAILYBRIEFINGWEHAVEAVARIETYOFPROGRAMSASPARTOFOUROVERALLCOUNTERNARCOTICSSUPPORTWITHCOUNTRIESINTHEREGIONBUTPENDINGTHISINVESTIGATIONWESUSPENDTHATASPECTOFTHESEPROGRAMSTHATSPECIALAERIALINTERCEPTPROGRAMHEADDEDUNDERTHEPERUVIANPROGRAMPERSONNELCONTRACTEDBYTHEAMERICANCENTRALINTELLIGENCEAGENCYFLYOVERTHECOUNTRYMONITORINGFLIGHTSBYSMALLPLANESTHATMIGHTBECARRYINGCOCAINEWHENTHEYFINDASUSPECTPLANETHEYGIVETHEDETAILSTOPERUVIANAUTHORITIESOVERCOLOMBIAPLANESMANNEDBYAMERICANPERSONNELANDPAIDFORWITHAMERICANGOVERNMENTMONEYPERFORMASIMILARFUNCTIONASPOKESMANFORSOUTHCOMTHEAMERICANMILITARYHEADQUARTERSRESPONSIBLEFORSURVEILLANCEFLIGHTSFROMECUADORCURACAOANDELSALVADORSAIDITSOPERATIONSWERENOTAFFECTEDTHEMILITARYCOUNTERDRUGOPERATIONSINTHESOUTHCOMAR

Characters Counted: 2632
 
A 234   G 53   L 99   Q 4   V 37
B 30   H 115   M 60   R 182   W 32
C 96   I 213   N 196   S 172   X 0
D 98   J 0   O 190   T 222   Y 30
E 320   K 15   P 81   U 88   Z 0
F 65                        

The United States has suspended its aerial drug interception program over Colombia since the mistaken attack on a U.S. missionary plane flying over Peru on Friday, the U.S. State Department said on Wednesday.

The United State suspended the aerial surveillance program over Peru last week after a Peruvian Air Force plane shot at the missionaries in their small plane over eastern Peru, killing an American woman and her child.

``The intercept program has been suspended also in Colombia,'' State Department spokesman Philip Reeker told his daily briefing.

``We have a variety of programs as part of our overall counternarcotics support with countries ... in the region, but pending this investigation we suspend that aspect of these programs, that special aerial intercept program,'' he added.

Under the Peruvian program, personnel contracted by the U.S. Central Intelligence Agency fly over the country, monitoring flights by small planes that might be carrying cocaine. When they find a suspect plane, they give the details to Peruvian authorities.

Over Colombia, planes manned by U.S. personnel and paid for with U.S. government money perform a similar function.

A spokesman for SOUTHCOM, the U.S. military headquarters responsible for surveillance flights from Ecuador, Curacao and El Salvador, said its operations were not affected.
 

Part 3