ENGLISH LETTER FREQUENCIES
ETOAN IRSHL DCUP FM WY

Okay, so it's not quantitative, but it's how I remember the relative frequency of letters in the English language, and it serves to explain why I chose this domain name.

Here's some more detail on statistical occurences of letters in the English language.

Letter Percent
E 13
T 9
O 8
A 8
N 7
I 7
R 7
S 6
H 6
L 4
Letter Percent
D 4
C 3
U 3
P 3
F 3
M 2
W 2
Y 2
B 1
Letter Percent
G 1
V 1
K <1
Q <1
X <1
J <1
Z <1

So, in set of 100 letters of English text, on average 13 of them would be 'E', 9 would be 'T', and so on.

GENERATING RANDOM NUMBERS
Click here for an explanation of my set-up to generate random numbers from a common radioactive source.

If you're looking for alternatives, here is a simple electronic number generator from 1976. I would not recommend it for serious cryptographic use, but it's neat to build nonetheless.

REFERENCES
  • The Handbook of Applied Cryptography by Alfred J. Menezes, Paul C. van Oorschot and Scott A. Vanstone is available on-line here.

  • The Cryptology ePrint Archive for 2004 can be found here.

QUOTES
From the 1984 movie Repo Man:

Leila: Are you using a scrambler?
J. Frank: I can't hear you, I'm using a scrambler!

 

From the 1976 movie Midway:

Captain Garth: How much can you decipher?
Commander Rochefort: Fifteen percent...
Garth: Really decipher?
Rochefort: Ten percent.
Garth: That's one word in ten, Joe! You're guessing!
Rochefort: We like to call it "analysis."

(In reality, Commander Joseph J. Rochefort was the OIC (officer-in-charge) of the Communications Intelligence processing unit in Hawaii, part of OP-20-G, the Navy Radio Intelligence Section. He was in daily contact with Lieutenant Commander Edwin Layton, who was the intelligence officer for Admiral Chester W. Nimitz, Commander-in-Chief, Pacific Fleet. Layton later wrote a book entitled "And I Was There..." detailing his activities before and during World War II.)

 

From comedienne Elayne Boosler:

"I have six locks on my door all in a row. When I go out, I lock every other one. I figure no matter how long somebody stands there picking the locks, they are always locking three."

 

Amateurs study cryptography; professionals study economics.
    -- Allan Schiffman, 2 July 04

DIGRAPH FREQUENCY TABLE
ASCII digraph Relative Frequency
(e_ = 100.0) 		Reverse/Forward Ratio
e_ 100.0 10.6%
_t 76.7 54.5%
th 60.8 1.9%
he 57.5 0.2%
s_ 52.8 47.2%
_a 44.8 26.6%
t_ 41.8 183.4%
re 39.8 88.6%
in 37.2 9.1%
CRLF 36.9 28.1%
er 35.2 112.9%
d_ 32.9 56.3%
n_ 30.3 38.1%
_i 29.7 1.6%
an 28.5 19.4%

KERCKHOFF'S PRINCIPLES
Auguste Kerckhoffs' Principles:

  • The system must be physically, if not mathematically, undecipherable;
  • The system must not require secrecy and can be stolen by the enemy without causing trouble;
  • It must be easy to communicate and remember the keys without requiring written notes, it must also be easy to change or modify the keys with different participants;
  • The system ought to be compatible with telegraph communication;
  • The system must be portable, and its use must not require more than one person;
  • Finally, regarding the circumstances in which such system is applied, it must be easy to use and must neither require stress of mind nor the knowledge of a long series of rules.

    • INTELLIGENT NOISE
    In the late 1970's a team of engineers in Seattle designed a secure telephone they called the PhasorPhone. Their attempt to have the design patented resulted in a secrecy order issued at the direction of the National Security Agency (NSA). Some brief exerpts from James Bamford's book The Puzzle Palace describing the situation can be seen by clicking here.

    The original design of the PhasorPhone was prompted by an article entitled Intelligent Noise which appeared in the December 1962 issue of Analog magazine. You can read the article by clicking here.

    ENCRYPTION TYPES
    Type 1   U.S. Classified
    Type 2   U.S. Federal interagency
    Type 3   Interoperable interagency (Federal, State and Local)
    Type 4   Proprietary

    PAPER ENGIMA MACHINE
    Mike Koss has put together a basic model of the Engima encipherment method using just a sheet a paper. You can read more about it here.
    ENCRYPTION USED BY THE KNIGHTS TEMPLAR
    Question for the reader: are there any good references for details regarding the coding scheme used by the Knights Templar during the Middle Ages for their "letters of credit"?
    By 1150, the Order's original mission of guarding pilgrims had changed into a mission of guarding their valuables through an innovative way of issuing letters of credit, an early precursor of modern banking. Pilgrims would visit a Templar house in their home country, depositing their deeds and valuables. The Templars would then give them an encrypted letter which would describe their holdings. While traveling, the pilgrims could present the letter to other Templars along the way, to "withdraw" funds from their account. This kept the pilgrims safe since they were not carrying valuables, and further increased the power of the Templars.
    (from Wikipedia)

    ACA COMPUTER SUPPLEMENTS
    You can find the programs and data files associated with the American Cryptogram Association Computer Supplement by clicking here.

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    Last updated October 14, 2007