If solving a cryptogram depends upon being able to distinguish between
four general cases (though two in essence):
1) separators exist and are in the clear:
2) separators exist but are encrypted:
3) separators exist but are artificial ['c' is padded at end]:
4) separators do not exist:
The second two are equivalent in that the existence of artifical separators
are as useless as the non-existence of separators since words are not
distinguishable (which is important for determining word lengths and
word patterns in some cases).
the fourth are nearly indistinguisable. Before taking action, the
cryptanalyst must decide which is the case. I could just recursively
parse and see if any results occur (parsing through the EverCrack Kernel) or I
could perform a frequency count.
I could replace those characters with a space and run it through the
kernel or I could (if the text is long enough) perform a frequency
analysis of the length of the words - calculate the average distance
for that cipher symbol. The average distance between spaces in text
is approximately 5.0 (which implies by default that the average length
of words is 4).
correct then it is most likely that either there are no separators
used or the cipher text has undergone transposition. If the latter
is the case, then the cryptanalyst must submit the ciphertext to
different transpositions until the separators match the average
distance variance (if not, then it is *certainly* the case that
no separators are used).
imately 5.0, it can be statistically assumed that that cipher-symbol
is indeed a separator and replaced accordingly. This one discovery
has now provided more information to the cryptanalyst; the length
of all words and the linguistic pattern of each of those words in
the cipher-text [the pattern is only discernable if it is a mono-
transposition cipher. If it is a substitution cipher the ciphertext
must be iteratively parsed with each parsed-pattern sequence (of 'words')
cryptanalyzed. If it is a transposition cipher the cipher-text is simply
parsed after various rounds of transposition and tested against dictionary
words (using either specific or general implementation cipher crackers).
Keys represent a particular implementation of an enciphering method.
alphabetic and polyalphabetic systems. Generally, a monoalphabetic
system is not considered to use a key, but essentially, it does.
Consider the Caesar cipher, in its general class as a displacement
cipher. The cipher used a standard, direct cipher alphabet [the
letters were in alphabetic order in the standard left-to-right
direction]. Generalizing away from the specific implementation
of rotating the alphabet 13 positions [in which case the key was
the method or algorithm itself - which was secret], although the
cryptanalyzer may know the method, the cipher alphabet could have
been shifted any of 25 positions. The key in this case, is the
specific number of shifts employed to encipher the message.
message, the key is really the specific cipher alphabet used
[as in the Caesar shift, the number of shifts represented the
specific cipher alphabet used]. In the polyalphabetic system,
the key [its length] represents the number of alphabets used
[that number out of a pool of (26! - 1) alphabets.
to cryptanalyze the key] and the strength of the encryption [how
difficult it would be to cryptanalyze the message].
will be used]. Generally, the longer the key the better [ideally,
a key of equal length to the message being encrypted would be very
secure since the length of the key would be of less use in cracking
the encrypted message].
letters, letters and numbers, or any ASCII character, etc.,].
The more tokens available for the key make it only marginally
tougher to cryptanalyze than the length of the key. Increasing
the length of the key increases the key space exponentially
whereas increasing the symbol space of the key increases the
key space linearly. If a key consists of five symbols [only
lower-case letters of the alphabet] the key space equals
11,881,376 possibilities. Now by doubling the symbol space
to include upper-case letters the key space now equals 380,204,032,
which is significantly greater. However, by retaining the initial
symbol space and doubling the key length the key space
equals a whopping 141,167,095,653,376 possibilities! Key strength
can be calculated as follows: [symbol space] ^ [key length].
By doubling the symbol space the key space only increased by a
few tenfolds whereas by doubling the key length the key space
increased by a few thousand-folds
structure [frequency distribution of the letters].
Since all languages have structural properties particular to them,
of a cipher text.
most closely matches that of the cipher text. This method can be
used for both substitution and transposition ciphers.
calculates the IC then compares that value against the IC values of
known languages. The IC value which it varies the least from is the
language it chooses as the best guess. At this point you have a
better idea of which dictionary set to use to crack the cipher.
against the frequency distribution of a particular language. This is
primarily only useful for discriminating against a pool of languages
that share similar alphabetic symbols (i.e., English and German).
Padding is primarily applied to Transposition ciphers for completing
padding also serves the dual purpose of hiding the frequency
distribution from a cryptanalyzer. Transposition systems that
do not include substitution leave the frequency distribution of
the letters in the clear.
distribution [IOC] which can make it more difficult for the
cryptanalyzer to; identify the type of cipher and identify the
language of the message.
generated matrix [this method can inform the cryptanalyzer to the
particular geometrical figure used to transpose the message].
EverCrack has only one method for dealing with pads in trans-
position ciphers [albeit, relatively weak]. Using the Matrix Cracker
generates all possible geometric figures and sends eachresult to a parser which traverses through the resulting text
trying to build words that match against the dictionary.
Punctuation in cipher-text can present problems similar to
I would have to say that the first indication that punctuation is
being used [and encrypted] would be if the total number of cipher
text symbols exceeded the number of letters in the target
languages alphabet [of course for short messages where
not all letters were used this is more of a problem].
Using statistical analysis, one may be able to figure out which
cipher symbols are punctuation marks [and probably simply
remove them from the text].