| |  |
As
well as the analysis of letter frequencies, other patterns can also be detected
that may help to decipher a piece of ciphertext.
The
following text explains some of the clues that can be used to deduce a word or
a letter in a piece of ciphertext. If you scroll further down the page, you will
see a list of tables that explain letter frequencies and patterns in other languages.
This
will prove useful for breaking messages not written in English.
Identify
Common Pairs Of Letters: If the ciphertext appears to encode a message in
English, but the plaintext does not reveal itself immediately, which is often
the case, then focus on pairs of repeated letters. In English the most common
repeated letters are ss, ee, tt, ff, ll, mm and oo. If the ciphertext contains
any repeated characters, you can assume that they represent one of these. Identify
The Smallest Words First: If the ciphertext contains spaces between words,
then try to identify words containing just one, two or three letters. The only
one-letter words in English are a and I. The most common two-letter words are
of, to, in, it, is, be, as, at, so, we, he, by, or, on, do, if, me, my, up,
an, go, no, us, am. The most common three-letter words are the and and. Tailor
Made Frequency Tables: If possible, tailor the table of frequencies to the
message you are trying to decipher. E.g., military messages tend to omit pronouns
and articles, and the loss of words such as I, he, a and they will reduce the
frequency of some of the commonest letters. If you know you are tackling a military
message, you should use a frequency table generated from other military messages. Play
The Guessing Game: This can be one of the most useful skills for a cryptanalyst
to employ - the ability to identify words, or even entire phrases, based on experience
or sheer guesswork. Al-Khalil, an early Arabian cryptanalyst, demonstrated this
talent when he cracked a Greek ciphertext. He guessed that the ciphertext began
with the greeting 'In the name of God'. Having established that these letters
corresponded to a specific section of ciphertext, he could use them as a crowbar
to prise open the rest of the ciphertext. This is known as a crib.
Letter and word frequencies have been analysed in a number of different languages.
A few of the most commonly used ones are listed below, and may help you to decipher
your secret messages…
ENGLISH
|
Order Of
Frequency Of Single Letters | E
T A O I N S H R D L U | | | |
| Order
Of Frequency Of Digraphs | th
er on an re he in ed nd ha at en es of or nt ea ti to it st io le is ou ar as
de rt ve | | | |
| Order
Of Frequency Of Trigraphs | the
and tha ent ion tio for nde has nce edt tis oft sth men | | | |
| Order
Of Frequency Of Most Common Doubles | ss
ee tt ff ll mm oo | | | |
| Order
Of Frequency Of Initial Letters | T
O A W B C D S F M R H I Y E G L N P U J K | | | |
| Order
Of Frequency Of Final Letters |
E S T D N R Y F L O G H A K M P U W | | | |
| One-Letter
Words | a,
I. | | | |
| Most
Frequent Two-Letter Words | of,
to, in, it, is, be, as, at, so, we, he, by, or, on, do, if, me, my, up, an, go,
no, us, am | | | |
| Most
Frequent Three-Letter Words | the,
and, for, are, but, not, you, all, any, can, had, her, was, one, our, out, day,
get, has, him, his, how, man, new, now, old, see, two, way, who, boy, did, its,
let, put, say, she, too, use | | | |
| Most
Frequent Four-Letter Words | that,
with, have, this, will, your, from, they, know, want, been, good, much, some,
time | |
FRENCH
|
Order Of
Frequency Of Single Letters | E
N A S R I U T O L D C M P V F B G X H Q Y Z J K W | | | |
| Most
Common Digraphs | es
en le de on ou nt re ne ed te em se er ar me an it et ie ti el ns ur |
| | |
| Most
Common Trigraphs | ede
les lle que ait eme ion eur ell sse est dan del men des tio ese ans ter ons qui
ais ous ent | | | |
| Most
Frequent Doubles | ss
ll ee nn tt ff cc rr mm pp | | | |
| One-Letter
Words: | a,
y, o | | | |
| Most
Common Two-Letter Words | au,
ce, ci, de, du, en, et, il, je, la, Ie, ma, me, ne, ni, on, ou, sa, se, si, un
au | |
GERMAN
|
Order
Of Frequency Of Single Letters | E
N R I S T U D A H G L O C M B Z F W K V P J Q X Y | | |
| Most
Common Digraphs | en
er ch de ge ei ie in ne be el te un st di un ue se au re he it ri tz |
| |
| Most
Common Trigraphs | ein
ich den der ten cht sch che die ung gen und nen des ben rch | | |
| Most
Frequent Doubles | ee
tt ll ss dd mm nn | | |
| Common
Two-Letter Words | ab,
am, an, da, er, es, ob, so, wo, im, in, um, zu, du, ja ab | |
ITALIAN
|
Order Of
Frequency Of Single Letters | E
I A O R L N T S C D P U M G V H Z B F Q J K W X Y | | | |
| Most
Common Digraphs | er
es on re de di ti si el en la al nt ra co ta to le li an in io ar or |
| | |
| Most
Common Trigraphs | che
ere zio del que ari ato eco edi ide esi idi ero par nte sta men |
| | |
| Most
Frequent Doubles | ll
ss tt ee pp nn bb gg cc | | | |
| One-Letter
Words: | e,
a, i, o | | | |
| Most
Common Two-Letter Words | di,
in, ha, ho | |
SPANISH
|
Order Of
Frequency Of Single Letters | E
A O S R I N L D C T U P M Y Q G B H F V J Z K W X | | | |
| Most
Common Digraphs | es
en el de la os ar ue ra re er as on st
ad ai or ta co se ac ec ci ia | | | |
| Most
Common Trigraphs | que
est ara ado aqu del cio nte osa ede
per ist nei res sde | | | |
| Most
Frequent Doubles | ee
ll rr aa ss cc dd nn | | | |
| One-Letter
Words | a,
e, o, u, y | | | |
| Most
Common Two-Letter Words: | en,
la, de, Io, el, se | |
| |
|
