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    <article-meta>
      <title-group>
        <article-title>Decryption Through the Likelihood of Frequency of Letters</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Barbara Sa</string-name>
        </contrib>
        <contrib contrib-type="author">
          <string-name>nchez Rinza</string-name>
          <email>brinza@cs.buap.mx</email>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Fernando Zacarias Flores</string-name>
          <email>fzflores@yahoo.com.mx</email>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Luna P</string-name>
        </contrib>
        <contrib contrib-type="author">
          <string-name>erez Mauricio</string-name>
        </contrib>
        <contrib contrib-type="author">
          <string-name>inez Cort</string-name>
        </contrib>
        <contrib contrib-type="author">
          <string-name>es Marco Antonio</string-name>
        </contrib>
      </contrib-group>
      <fpage>57</fpage>
      <lpage>62</lpage>
      <abstract>
        <p>The method to decrypt the information using probability leads to a more thorough job, because you have to know the percentage of each of the letters of the language that is being analyzed here is Spanish. You can consider not only the probabilities of the letters also syllables, set of three, four letters and even words. Then you have this thing to do is make comparisons of the frequencies of cipher text and the frequencies of the language to begin to replace by a correspondence. And ¯nally passing a scanner and ¯nd the decrypted text.</p>
      </abstract>
      <kwd-group>
        <kwd>Probability</kwd>
        <kwd>Decrypt</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>Introduction</title>
      <p>
        Cryptography is the science that alters the linguistic representations of a message
[
        <xref ref-type="bibr" rid="ref1">1</xref>
        ]. For this there are di®erent methods, where the most common is encryption.
This science masking the original references of the information by a conversion
method governed by an algorithm that allows the reverse or decryption of
information. Use of this or other techniques, allowing for an exchange of messages
that can only be read by the intended bene¯ciaries as 'consistent'. A consistent
recipient is the person to whom the message is directed with the intention of
the sender. Thus, the recipient knows the discrete coherent used for masking the
message. So either have the means to bring the message to the reverse process
cryptographic, or can infer the process that becomes a message to the public. The
original information to be protected is called plaintext or cleartext. Encryption
is the process of converting plain text into unreadable gibberish called
ciphertext or cryptogram. In general, the concrete implementation of the encryption
algorithm (also called ¯gure) is based on the existence of key secret information
that ¯ts the encryption algorithm for each di®erent use [
        <xref ref-type="bibr" rid="ref2">2</xref>
        ].
      </p>
      <p>
        Decryption is the reverse process to recover the plaintext from the ciphertext
and key. Cryptographic protocol speci¯es the details of how to use algorithms
and keys (and other primitive operations) to achieve the desired e®ect. The set
of protocols, encryption algorithms, key management processes and actions of
the users, which together constitute a cryptosystem, which is what the end user
works and interacts. In this work, we must ¯rst have a ciphertext which must
meet certain requirements, such a text should be bijective so that each element
of the domain carries a single element of the condominium. In addition we must
also take account of the rules of Kerckho® [
        <xref ref-type="bibr" rid="ref3">3</xref>
        ].
2
2.1
      </p>
    </sec>
    <sec id="sec-2">
      <title>Development work</title>
      <sec id="sec-2-1">
        <title>Frequencies in Spanish</title>
        <p>
          Is required to decrypt text using the odds as to how often they used certain
letters in the alphabet, for this work only considered the Spanish language [
          <xref ref-type="bibr" rid="ref5">5</xref>
          ].
        </p>
        <p>The frequencies of Spanish, which were used for this study were:
1. Frequency triglyphs
2. Frequency of digraphs
3. Most common words
4. Frequency of letters at the beginning of words
5. Frequency of letters in Spanish
6. Frequency Words
2.2</p>
      </sec>
      <sec id="sec-2-2">
        <title>Triglyphs Frequencies</title>
        <p>The letter frequency statistics may vary from one to another depending on the
corpus author has chosen to develop them. Usually di®erences when the corpus
is literary or consists of texts of di®erent origins. Table 1 shows the frequency of
each of the Spanish alphabet with their respective percentage.
2.3</p>
      </sec>
      <sec id="sec-2-3">
        <title>Most Frequent words</title>
        <p>
          The vowels make up about 46.38% of the text. The high frequency letters account
for 67.56% of the text. Mid-frequency points accounting for 25% of the text [
          <xref ref-type="bibr" rid="ref4">4</xref>
          ].
In the dictionary the most common vowel is A, but in written texts is the E
because of prepositions, conjunctions, verbs, etc. The most common consonants
are L, S, N, D, with about 30%. The less frequent six letters: V, N, J, Z, X and
K (just over 1%). The average frequency of a Spanish word is 5.9 letters. The
coincidence index for Spanish is 0.0775. In addition to solving the encryption
table 2 we mentioned that we most frequently used words in a text of 10 000
words.
        </p>
        <p>Next, table 3 shows the frequencies of the 4-letter words.
The size of the corpus is 60,115 letters. The frequencies are absolute. The
digraphs are read by row and column in that order. Below in table 4 shows the
union digraphs are letters from letters.
The ciphertext is used as said it had to be bijective and have Kerckho® rules
and the decrypted text shown in Figure 1.
Four-letter words Distribution of letters in literary texts
Word Frequency E - 16,78% R - 4,94% Y - 1,54% J - 0,30%
PARA 67 A - 11,96% U - 4,80% Q - 1,53%
COMO 36 O - 8,69% I - 4,15% B - 0,92%
AYER 25 L - 8,37% T - 3,31% H - 0,89%
ESTE 23 S - 7,88% C - 2,92% G - 0,73%
PERO 18 N - 7,01% P - 2,77% F - 0,52%
ESTA 17 D - 6,87% M - 2,12% V - 0,39%
AOS 14
TODO 11
SIDO 11
SOLO 10
We conclude that this method of decryption is good however would have to
tweak a little more due to it depends on the text we have and how much text
to decrypt was also observed that only decrypts an encrypted bijective. In this
work, as seen in the results of Figure 1, which apply various processes, ¯rst see
the probability of the lyrics in Spanish that are more frequent, then seen with
the syllables that are more frequent in Spanish, and then with the last word and
you miss the information, text analyzer, as shown in Figure 1 a large percentage
of the information is decoded, but as mentioned in the top, this will depend have
that much information to process it.</p>
      </sec>
    </sec>
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  <back>
    <ref-list>
      <ref id="ref1">
        <mixed-citation>
          <article-title>1. Liddell and Scott's Greek-English Lexicon</article-title>
          . Oxford University Press. (
          <year>1984</year>
          )
        </mixed-citation>
      </ref>
      <ref id="ref2">
        <mixed-citation>
          2.
          <string-name>
            <given-names>Anaya</given-names>
            <surname>Multimedia</surname>
          </string-name>
          ,
          <string-name>
            <surname>Codigos Y Claves Secretas: Programas En</surname>
            <given-names>Basic</given-names>
          </string-name>
          ,
          <article-title>Basado A Su Vez En Un Estudio Lexicogr¯co Del Diario "El Pas"</article-title>
          ,
          <year>Mexico 1986</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref3">
        <mixed-citation>
          3.
          <string-name>
            <surname>Friedman</surname>
          </string-name>
          , William F. And
          <string-name>
            <surname>Callimahos</surname>
            ,
            <given-names>Lambros D.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Military</surname>
            <given-names>Cryptanalytics</given-names>
          </string-name>
          , Cryptographic Series,
          <year>1962</year>
        </mixed-citation>
      </ref>
      <ref id="ref4">
        <mixed-citation>
          4.
          <string-name>
            <surname>Part</surname>
            <given-names>I</given-names>
          </string-name>
          - Volume
          <volume>2</volume>
          , Aegean Park Press, Laguna Hills, Ca,
          <year>1985</year>
        </mixed-citation>
      </ref>
      <ref id="ref5">
        <mixed-citation>
          5.
          <string-name>
            <surname>Barker</surname>
          </string-name>
          , Wayne G., Cryptograms In Spanish, Aegean Park Press, Laguna Hills, Ca.,
        </mixed-citation>
      </ref>
    </ref-list>
  </back>
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