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<title>Classical cipher</title>

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<span id="openzim-page-title" class="mw-page-title-main"><span class="mw-page-title-main">Classical cipher</span></span>

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<p>In <a href="Cryptography" title="Cryptography">cryptography</a>, a <b>classical cipher</b> is a type of <a href="Cipher" title="Cipher">cipher</a> that was used historically but for the most part, has fallen into disuse. In contrast to modern cryptographic algorithms, most classical ciphers can be practically computed and solved by hand. However, they are also usually very simple to break with modern technology. The term includes the simple systems used since Greek and Roman times, the elaborate Renaissance ciphers, World War II cryptography such as the <a href="Enigma_machine" title="Enigma machine">Enigma machine</a> and beyond.

</p><p>In contrast, modern <a href="Strong_cryptography" title="Strong cryptography">strong cryptography</a> relies on new algorithms and computers developed since the 1970s.

</p>

<div class="mw-heading mw-heading2"><h2 id="Types_of_classical_ciphers">Types of classical ciphers</h2></div>

<p>Classical ciphers are often divided into <i><a href="Transposition_cipher" title="Transposition cipher">transposition ciphers</a></i> and <i><a href="Substitution_cipher" title="Substitution cipher">substitution ciphers</a></i>, but there are also <i><a href="Null_cipher" title="Null cipher">concealment ciphers</a></i>.

</p>

<div class="mw-heading mw-heading3"><h3 id="Substitution_ciphers">Substitution ciphers</h3></div>

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</style><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="Substitution_cipher" title="Substitution cipher">Substitution cipher</a></div>

<p>In a substitution cipher, letters, or groups of letters, are systematically replaced throughout the message for other letters, groups of letters, or symbols.

</p><p>A well-known example of a substitution cipher is the <a href="Caesar_cipher" title="Caesar cipher">Caesar cipher</a>. To encrypt a message with the Caesar cipher, each letter of message is replaced by the letter three positions later in the alphabet. Hence, A is replaced by D, B by E, C by F, etc. Finally, X, Y and Z are replaced by A, B and C respectively. So, for example, "WIKIPEDIA" encrypts as "ZLNLSHGLD". Caesar rotated the alphabet by three letters, but any number works.

</p><p>Another method of substitution cipher is based on a keyword. All spaces and repeated letters are removed from a word or phrase, which the encoder then uses as the start of the cipher alphabet. The end of the cipher alphabet is the rest of the alphabet in order without repeating the letters in the keyword. For example, if the keyword is CIPHER, the cipher alphabet would look like this:

</p>

<th>normal alphabet

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.mw-parser-output .monospaced{font-family:monospace,monospace}

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</style><span class="monospaced">a b c d e f g h i j k l m n o p q r s t u v w x y z</span>

</td></tr>

<tr>

<th>cipher alphabet

</th>

</td></tr></tbody></table>

<p>The previous examples were all examples of monoalphabetic substitution ciphers, where just one cipher alphabet is used. It is also possible to have a <a href="Polyalphabetic_cipher" title="Polyalphabetic cipher">polyalphabetic substitution cipher</a>, where multiple cipher alphabets are used. The encoder would make up two or more cipher alphabets using whatever techniques they choose, and then encode their message, alternating what cipher alphabet is used with every letter or word. This makes the message much harder to decode because the codebreaker would have to figure out both cipher alphabets.

</p><p>Another example of a polyalphabetic substitution cipher that is much more difficult to decode is the <a href="Vigenere_square" class="mw-redirect" title="Vigenere square">Vigenère square</a>, an innovative encoding method. With the square, there are 26 different cipher alphabets that are used to encrypt text. Each cipher alphabet is just another rightward Caesar shift of the original alphabet. This is what a Vigenère square looks like:

</p>

<pre> A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

B C D E F G H I J K L M N O P Q R S T U V W X Y Z A

C D E F G H I J K L M N O P Q R S T U V W X Y Z A B

D E F G H I J K L M N O P Q R S T U V W X Y Z A B C

E F G H I J K L M N O P Q R S T U V W X Y Z A B C D

F G H I J K L M N O P Q R S T U V W X Y Z A B C D E

G H I J K L M N O P Q R S T U V W X Y Z A B C D E F

H I J K L M N O P Q R S T U V W X Y Z A B C D E F G

I J K L M N O P Q R S T U V W X Y Z A B C D E F G H

J K L M N O P Q R S T U V W X Y Z A B C D E F G H I

K L M N O P Q R S T U V W X Y Z A B C D E F G H I J

L M N O P Q R S T U V W X Y Z A B C D E F G H I J K

M N O P Q R S T U V W X Y Z A B C D E F G H I J K L

N O P Q R S T U V W X Y Z A B C D E F G H I J K L M

O P Q R S T U V W X Y Z A B C D E F G H I J K L M N

P Q R S T U V W X Y Z A B C D E F G H I J K L M N O

Q R S T U V W X Y Z A B C D E F G H I J K L M N O P

R S T U V W X Y Z A B C D E F G H I J K L M N O P Q

S T U V W X Y Z A B C D E F G H I J K L M N O P Q R

T U V W X Y Z A B C D E F G H I J K L M N O P Q R S

U V W X Y Z A B C D E F G H I J K L M N O P Q R S T

V W X Y Z A B C D E F G H I J K L M N O P Q R S T U

W X Y Z A B C D E F G H I J K L M N O P Q R S T U V

X Y Z A B C D E F G H I J K L M N O P Q R S T U V W

Y Z A B C D E F G H I J K L M N O P Q R S T U V W X

Z A B C D E F G H I J K L M N O P Q R S T U V W X Y

</pre>

<p>To use the Vigenère square to encrypt a message, a coder first chooses a keyword to use and then repeats it until it is the same length as the message to be encoded. If <span class="monospaced">LEMON</span> is the keyword, each letter of the repeated keyword will tell what cipher (what row) to use for each letter of the message to be coded. The cipher alphabet on the second row uses B for A and C for B etc. That is cipher alphabet 'B'. Each cipher alphabet is named by the first letter in it. For example, if the keyword is <span class="monospaced">LEMON</span> and the message to encode is <span class="monospaced">ATTACKATDAWN</span>, then the encoding is:

</p>

<th>Plaintext

</th>

<td><span class="monospaced">ATTACKATDAWN</span>

</td></tr>

<tr>

<th>Key

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<td><span class="monospaced">LEMONLEMONLE</span>

</td></tr>

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<th>Ciphertext

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<td><span class="monospaced">LXFOPVEFRNHR</span>

</td></tr></tbody></table>

<p>Some substitution ciphers involve using numbers instead of letters. An example of this is the <a href="Great_Cipher" title="Great Cipher">Great Cipher</a>, where numbers were used to represent syllables. There is also another number substitution cipher that involves having four different number pair options for a letter based

on a keyword.

</p><p>Instead of numbers, symbols can also be used to replace letters or syllables. One example of this is <a href="Zodiac" title="Zodiac">Zodiac</a> alphabet, where signs of the zodiac were used to represent different letters, for example, the symbols for the sun stood for A, Jupiter stood for B, and Saturn stood for C. Dots, lines, or dashes could also be used, one example of this being <a href="Morse_Code" class="mw-redirect" title="Morse Code">Morse Code</a>, which is not a cipher, but uses dots and dashes as letters nonetheless. The <a href="Pigpen_cipher" title="Pigpen cipher">pigpen cipher</a> uses a grid system or lines and dots to establish symbols for letters. There are various other methods that involve substituting letters of the alphabet with symbols or dots and dashes.

</p>

<div class="mw-heading mw-heading3"><h3 id="Transposition_ciphers">Transposition ciphers</h3></div>

<div role="note" class="hatnote navigation-not-searchable">Main article: <a href="Transposition_cipher" title="Transposition cipher">Transposition cipher</a></div>

<p>In a transposition cipher, the letters themselves are kept unchanged, but their order within the message is scrambled according to some well-defined scheme. Many transposition ciphers are done according to a geometric design. A simple (and once again easy to crack) encryption would be to write every word backwards. For example, "Hello my name is Alice." would now be "olleH ym eman si ecilA." A <a href="Scytale" title="Scytale">scytale</a> is a machine that aids in the transposition of methods.

</p><p>In a columnar cipher, the original message is arranged in a rectangle, from left to right and top to bottom. Next, a key is chosen and used to assign a number to each column in the rectangle to determine the order of rearrangement. The number corresponding to the letters in the key is determined by their place in the alphabet, i.e. A is 1, B is 2, C is 3, etc. For example, if the key word is CAT and the message is THE SKY IS BLUE, the message would be arranged thus:

</p>

<pre> C A T

3 1 20

T H E

S K Y

I S B

L U E

</pre>

<p>Next, the letters are taken in numerical order and that is how the message is transposed. The column under A is taken first, then the column under C, then the column under T, as a result the message "The sky is blue" has become: HKSUTSILEYBE

</p><p>In the Chinese cipher's method of transposing, the letters of the message are written from right to left, down and up columns to scramble the letters. Then, starting in the first row, the letters are taken in order to get the new <a href="Ciphertext" title="Ciphertext">ciphertext</a>. For example, if the message needed to be enciphered was THE DOG RAN FAR, the Chinese cipher would look like this:

</p>

<pre> R R G T

A A O H

F N D E

</pre>

<p>The cipher text then reads: RRGT AAOH FNDE

</p><p>Many transposition ciphers are similar to these two examples, usually involving rearranging the letters into rows or columns and then taking them in a systematic way to transpose the letters. Other examples include the Vertical Parallel and the Double Transposition Cipher.

</p><p>More complex <a href="Algorithm" title="Algorithm">algorithms</a> can be formed by mixing substitution and transposition in a <a href="Product_cipher" title="Product cipher">product cipher</a>; modern <a href="Block_cipher" title="Block cipher">block ciphers</a> such as <a href="Data_Encryption_Standard" title="Data Encryption Standard">DES</a> iterate through several stages of substitution and transposition.

</p>

<div class="mw-heading mw-heading3"><h3 id="Concealment_ciphers">Concealment ciphers</h3></div>

<div role="note" class="hatnote navigation-not-searchable">Main article: <a href="Null_cipher" title="Null cipher">Null cipher</a></div>

<p>Put simply, a concealment, or null, cipher is any cipher which involves a number of <i>nulls,</i> or decoy letters. A null cipher could be <a href="Plaintext" title="Plaintext">plaintext</a> words with nulls placed in designated areas or even a plaintext message broken up in different positions with a null at the end of each word.<sup id="cite_ref-:4_1-0" class="reference"><a href="#cite_note-:4-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> However, a message with only a couple nulls (for example, one at the beginning and one at the end) is <i>not</i> a null cipher.

</p><p>

For example, during <a href="English_Civil_War" title="English Civil War">England's Civil War</a> Royalist Sir John Trevanian was aided in his escape from a Puritan castle in <a href="Colchester" title="Colchester">Colchester</a> by this message:<sup id="cite_ref-:1_3-0" class="reference"><a href="#cite_note-:1-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup></p><blockquote><p>WORTHIE SIR JOHN, HOPE, THAT IS YE BESTE COMFORT OF YE AFFLICTED, CANNOT MUCH, I FEAR ME, HELP YOU NOW. THAT I WOULD SAY TO YOU, IS THIS ONLY: IF EVER I MAY BE ABLE TO REQUITE THAT I DO OWE YOU, STAND NOT UPON ASKING ME. TIS NOT MUCH THAT I CAN DO; BUT WHAT I CAN DO, BEE YE VERY SURE I WILL. I KNOW THAT, IF DETHE COMES, IF ORDINARY MEN FEAR IT, IT FRIGHTS NOT YOU, ACCOUNTING IT FOR A HIGH HONOUR, TO HAVE SUCH A REWARDE OF YOUR LOYALTY. PRAY YET YOU MAY BE SPARED THIS SOE BITTER, CUP. I FEAR NOT THAT YOU WILL GRUDGE ANY SUFFERINGS; ONLY IF BIE SUBMISSIONS YOU CAN TURN THEM AWAY, TIS THE PART OF A WISE MAN. TELL ME, AN IF YOU CAN, TO DO FOR YOU ANYTHINGE THAT YOU WOLDE HAVE DONE. THE GENERAL GOES BACK ON WEDNESDAY. RESTINGE YOUR SERVANT TO COMMAND.</p></blockquote><p>The third letter after each punctuation reveals "Panel at East end of Chapel slides".

</p><p>A dot or pinprick null cipher is a common classical encryption method in which dot or pinprick is placed above or below certain letters in a piece of writing.<sup id="cite_ref-:13_4-0" class="reference"><a href="#cite_note-:13-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> An early reference to this was when <a href="Aeneas_Tacticus" title="Aeneas Tacticus">Aeneas Tacticus</a> wrote about it in his book <i>On the Defense of Fortifications.</i><sup id="cite_ref-:3_5-0" class="reference"><a href="#cite_note-:3-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup>

</p>

<div class="mw-heading mw-heading2"><h2 id="Cryptanalysis_of_classical_ciphers">Cryptanalysis of classical ciphers</h2></div>

<p>Classical ciphers are commonly quite easy to break. Many of the classical ciphers can be broken even if the attacker only knows sufficient ciphertext and hence they are susceptible to a <a href="Ciphertext-only_attack" title="Ciphertext-only attack">ciphertext-only attack</a>. Some classical ciphers (e.g., the <a href="Caesar_cipher" title="Caesar cipher">Caesar cipher</a>) have a small key space. These ciphers can be broken with a <a href="Brute_force_attack" class="mw-redirect" title="Brute force attack">brute force attack</a>, that is by simply trying out all keys. <a href="Substitution_ciphers" class="mw-redirect" title="Substitution ciphers">Substitution ciphers</a> can have a large key space, but are often susceptible to a <a href="Frequency_analysis" title="Frequency analysis">frequency analysis</a>, because for example frequent letters in the plaintext language correspond to frequent letters in the ciphertexts. Polyalphabetic ciphers such as the <a href="Vigen%C3%A8re_cipher" title="Vigenère cipher">Vigenère cipher</a> prevent a simple frequency analysis by using multiple substitutions. However, more advanced techniques such as the <a href="Kasiski_examination" title="Kasiski examination">Kasiski examination</a> can still be used to break these ciphers.

</p><p>On the other hand, modern ciphers are designed to withstand much stronger attacks than ciphertext-only attacks. A good modern cipher must be secure against a wide range of potential attacks including <a href="Known-plaintext_attack" title="Known-plaintext attack">known-plaintext attacks</a> and <a href="Chosen-plaintext_attack" title="Chosen-plaintext attack">chosen-plaintext attacks</a> as well as <a href="Chosen-ciphertext_attack" title="Chosen-ciphertext attack">chosen-ciphertext attacks</a>. For these ciphers an attacker should not be able to find the key even if they know any amount of plaintext and corresponding ciphertext and even if they could select plaintext or ciphertext themselves. Classical ciphers do not satisfy these much stronger criteria and hence are no longer of interest for serious applications.

</p><p>Some techniques from classical ciphers can be used to strengthen modern ciphers. For example, the <a href="Rijndael_MixColumns" title="Rijndael MixColumns">MixColumns</a> step in <a href="Advanced_Encryption_Standard" title="Advanced Encryption Standard">AES</a> is a <a href="Hill_cipher" title="Hill cipher">Hill cipher</a>.<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup>

</p>

<ul><li><a href="History_of_cryptography" title="History of cryptography">History of cryptography</a></li></ul>

<div class="mw-heading mw-heading2"><h2 id="References">References</h2></div>

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</style><cite id="CITEREFTravisHindleyThomsonAmery1978" class="citation book cs1">Travis, Falcon; Hindley, Judy; Thomson, Ruth; Amery, Heather; Rawson, Christopher; Harper, Anita (1978). <i>The Spy's Guidebook</i>. Usborne Pocketbooks.</cite></span>

</li>

<li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text"><cite id="CITEREFMoore2019" class="citation book cs1">Moore, Gareth (2019). <i>Explorer Academy Codebreaking Activity Adventure</i>. National Geographic Books. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>9781426333071</bdi>.</cite></span>

</li>

<li id="cite_note-:1-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-:1_3-0">^</a></b></span> <span class="reference-text"><cite id="CITEREFJaneczko2004" class="citation book cs1">Janeczko, Paul B. (2004). <i>Top Secret: a Handbook of Codes, Ciphers, and Secret Writing</i>. Candlewick Press. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>9780763629724</bdi>.</cite></span>

</li>

<li id="cite_note-:13-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-:13_4-0">^</a></b></span> <span class="reference-text"><cite id="CITEREFJaneczko2004" class="citation book cs1">Janeczko, Paul B. (2004). <i>Top Secret: a Handbook of Codes, Ciphers, and Secret Writing</i>. Candlewick Press. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>9780763629724</bdi>.</cite></span>

</li>

<li id="cite_note-:3-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-:3_5-0">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://penelope.uchicago.edu/Thayer/E/Roman/Texts/Aeneas_Tacticus/E*.html">"Aeneas Tacticus • Siege Defense, XXI‑XXXI"</a>. <i>penelope.uchicago.edu</i><span class="reference-accessdate">. Retrieved <span class="nowrap">2022-05-28</span></span>.</cite></span>

</li>

<li id="cite_note-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-6">^</a></b></span> <span class="reference-text"><cite id="CITEREFXintong" class="citation web cs1">Xintong, Kit Choy. <a rel="nofollow" class="external text" href="https://www.angelfire.com/biz7/atleast/mix_columns.pdf">"Understanding AES Mix-Columns Transformation Calculation"</a> <span class="cs1-format">(PDF)</span><span class="reference-accessdate">. Retrieved <span class="nowrap">2016-10-26</span></span>.</cite></span>

</li>

</ol></div></div>

<ul><li><a rel="nofollow" class="external text" href="https://www.ciphermachinesandcryptology.com/en/handciphers.htm">Hand Ciphers</a> Pencil-and-paper ciphers on Ciphermachines & Cryptology</li>

<li><a rel="nofollow" class="external text" href="http://www.cs.trincoll.edu/~crypto/historical/">Trinity College Department of Computer Science: Historical Cryptography</a> Information about many different types of encryption algorithms including substitution and transposition ciphers</li>

<li><a href="Singh%2C_Simon" class="mw-redirect" title="Singh, Simon">Singh, Simon</a>. <a href="The_Code_Book%3A_The_Science_of_Secrecy_from_Ancient_Egypt_to_Quantum_Cryptography" class="mw-redirect" title="The Code Book: The Science of Secrecy from Ancient Egypt to Quantum Cryptography">The Code Book: The Science of Secrecy from Ancient Egypt to Quantum Cryptography</a>. New York: Anchor, 2000.</li>

<li>D'Agapeyeff, Alexander. Codes and Ciphers. Oxford UP, 1939.</li>

<li><a href="William_Friedman" class="mw-redirect" title="William Friedman">William Friedman</a>. <a rel="nofollow" class="external text" href="https://www.nsa.gov/Portals/75/documents/news-features/declassified-documents/friedman-documents/publications/FOLDER_267/41784809082383.pdf">American Army Field Codes In the American Expeditionary Forces During The First World War</a>, U.S. War Department, June 1942</li>

<li>Laffin, John. Codes and Ciphers: Secret Writing through the Ages. Abelard-Schuman, 1964.</li>

<li>Wrixon, Fred B. Codes, Ciphers, and Secret Languages. New York: Bonanza Books, 1989.</li></ul>

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</style></div><div role="navigation" class="navbox" aria-label="Navbox0" style="padding:3px"><table class="nowraplinks hlist navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><td colspan="2" class="navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><td colspan="2" class="navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="col" class="navbox-title" colspan="2"><div id="Classical_cryptography133" style="font-size:114%;margin:0 4em"></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Cipher" title="Cipher">Ciphers</a><br>by family</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%;font-weight:normal;"><a href="Polyalphabetic_cipher" title="Polyalphabetic cipher">Polyalphabetic</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Alberti_cipher" title="Alberti cipher">Alberti</a></li>

<li><a href="Enigma_machine" title="Enigma machine">Enigma</a></li>

<li><a href="Trithemius_cipher" class="mw-redirect" title="Trithemius cipher">Trithemius</a></li>

<li><a href="Vigen%C3%A8re_cipher" title="Vigenère cipher">Vigenère</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;font-weight:normal;"><a href="Polybius_square" title="Polybius square">Polybius square</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="ADFGVX_cipher" title="ADFGVX cipher">ADFGVX</a></li>

<li><a href="Bifid_cipher" title="Bifid cipher">Bifid</a></li>

<li><a href="Nihilist_cipher" title="Nihilist cipher">Nihilist</a></li>

<li><a href="Trifid_cipher" title="Trifid cipher">Trifid</a></li>

<li><a href="VIC_cipher" title="VIC cipher">VIC cipher</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;font-weight:normal;">Square</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Playfair_cipher" title="Playfair cipher">Playfair</a></li>

<li><a href="Two-square_cipher" title="Two-square cipher">Two-square</a></li>

<li><a href="Four-square_cipher" title="Four-square cipher">Four-square</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;font-weight:normal;"><a href="Substitution_cipher" title="Substitution cipher">Substitution</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Affine_cipher" title="Affine cipher">Affine</a></li>

<li><a href="Atbash" title="Atbash">Atbash</a></li>

<li><a href="Autokey_cipher" title="Autokey cipher">Autokey</a></li>

<li><a href="Beaufort_cipher" title="Beaufort cipher">Beaufort</a></li>

<li><a href="Caesar_cipher" title="Caesar cipher">Caesar</a></li>

<li><a href="Chaocipher" title="Chaocipher">Chaocipher</a></li>

<li><a href="Great_Cipher" title="Great Cipher">Great</a></li>

<li><a href="Pigpen_cipher" title="Pigpen cipher">Pigpen</a></li>

<li><a href="Running_key_cipher" title="Running key cipher">Running key</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;font-weight:normal;"><a href="Transposition_cipher" title="Transposition cipher">Transposition</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Transposition_cipher#Columnar_transposition" title="Transposition cipher">Columnar</a></li>

<li><a href="Transposition_cipher#Double_transposition" title="Transposition cipher">Double</a></li>

<li><a href="Transposition_cipher#Myszkowski_transposition" title="Transposition cipher">Myszkowski</a></li>

<li><a href="Rail_fence_cipher" title="Rail fence cipher">Rail fence</a></li>

<li><a href="Transposition_cipher#Route_cipher" title="Transposition cipher">Route</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;font-weight:normal;">Other</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="BATCO" title="BATCO">BATCO</a></li>

<li><a href="DRYAD" title="DRYAD">DRYAD</a></li>

<li><a href="Mlecchita_vikalpa" title="Mlecchita vikalpa">Kama Sutra</a></li>

<li><a href="Rasterschl%C3%BCssel_44" title="Rasterschlüssel 44">Rasterschlüssel 44</a></li>

<li><a href="Reihenschieber" title="Reihenschieber">Reihenschieber</a></li>

<li><a href="Reservehandverfahren" title="Reservehandverfahren">Reservehandverfahren</a></li>

<li><a href="Slidex" title="Slidex">Slidex</a></li>

<li><a href="Solitaire_(cipher)" title="Solitaire (cipher)">Solitaire</a></li></ul>

</div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Code_(cryptography)" title="Code (cryptography)">Codes</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

<li><a href="Code_talker" title="Code talker">Code talker</a></li>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Steganography" title="Steganography">Steganography</a></th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Bacon's_cipher" title="Bacon's cipher">Bacon</a></li>

<li><a href="Grille_(cryptography)" title="Grille (cryptography)">Grille</a></li>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Cryptanalysis</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Cryptogram" title="Cryptogram">Cryptogram</a></li>

<li><a href="Frequency_analysis" title="Frequency analysis">Frequency analysis</a></li>

<li><a href="Index_of_coincidence" title="Index of coincidence">Index of coincidence</a> (Units: <a href="Hartley_(unit)" title="Hartley (unit)">Ban</a> and <a href="Nat_(unit)" title="Nat (unit)">Nat</a>)</li>

<li><a href="Information_leakage" title="Information leakage">Information leakage</a></li>

<li><a href="Kasiski_examination" title="Kasiski examination">Kasiski examination</a></li></ul>

</div></td></tr></tbody></table><div></div></td></tr></tbody></table><div></div></td></tr><tr><td colspan="2" class="navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks mw-collapsible mw-collapsed navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="col" class="navbox-title" colspan="2"><div id="Cryptography149" style="font-size:114%;margin:0 4em"><a href="Cryptography" title="Cryptography">Cryptography</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%">General</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="History_of_cryptography" title="History of cryptography">History of cryptography</a></li>

<li><a href="Outline_of_cryptography" title="Outline of cryptography">Outline of cryptography</a></li>

<li><a href="Cryptographic_protocol" title="Cryptographic protocol">Cryptographic protocol</a>

<ul><li><a href="Authentication_protocol" title="Authentication protocol">Authentication protocol</a></li></ul></li>

<li><a href="Cryptographic_primitive" title="Cryptographic primitive">Cryptographic primitive</a></li>

<li><a href="Cryptanalysis" title="Cryptanalysis">Cryptanalysis</a></li>

<li><a href="Cryptocurrency" title="Cryptocurrency">Cryptocurrency</a></li>

<li><a href="Cryptosystem" title="Cryptosystem">Cryptosystem</a></li>

<li><a href="Cryptographic_nonce" title="Cryptographic nonce">Cryptographic nonce</a></li>

<li><a href="Cryptovirology" title="Cryptovirology">Cryptovirology</a></li>

<li><a href="Hash_function" title="Hash function">Hash function</a>

<ul><li><a href="Cryptographic_hash_function" title="Cryptographic hash function">Cryptographic hash function</a></li>

<li><a href="Key_derivation_function" title="Key derivation function">Key derivation function</a></li>

<li><a href="Secure_Hash_Algorithms" title="Secure Hash Algorithms">Secure Hash Algorithms</a></li></ul></li>

<li><a href="Digital_signature" title="Digital signature">Digital signature</a></li>

<li><a href="Kleptography" title="Kleptography">Kleptography</a></li>

<li><a href="Key_(cryptography)" title="Key (cryptography)">Key (cryptography)</a></li>

<li><a href="Key_exchange" title="Key exchange">Key exchange</a></li>

<li><a href="Key_generator" title="Key generator">Key generator</a></li>

<li><a href="Key_schedule" title="Key schedule">Key schedule</a></li>

<li><a href="Key_stretching" title="Key stretching">Key stretching</a></li>

<li><a href="Keygen" title="Keygen">Keygen</a></li>

<li>Machines</li>

<li><a href="Cryptojacking_malware" class="mw-redirect" title="Cryptojacking malware">Cryptojacking malware</a></li>

<li><a href="Ransomware" title="Ransomware">Ransomware</a></li>

<li><a href="Random_number_generation" title="Random number generation">Random number generation</a>

<ul><li><a href="Cryptographically_secure_pseudorandom_number_generator" title="Cryptographically secure pseudorandom number generator">Cryptographically secure pseudorandom number generator</a> (CSPRNG)</li></ul></li>

<li><a href="Pseudorandom_noise" title="Pseudorandom noise">Pseudorandom noise</a> (PRN)</li>

<li><a href="Secure_channel" title="Secure channel">Secure channel</a></li>

<li><a href="Insecure_channel" class="mw-redirect" title="Insecure channel">Insecure channel</a></li>

<li><a href="Subliminal_channel" title="Subliminal channel">Subliminal channel</a></li>

<li><a href="Encryption" title="Encryption">Encryption</a></li>

<li><a href="Decryption" class="mw-redirect" title="Decryption">Decryption</a></li>

<li><a href="End-to-end_encryption" title="End-to-end encryption">End-to-end encryption</a></li>

<li><a href="Harvest_now%2C_decrypt_later" title="Harvest now, decrypt later">Harvest now, decrypt later</a></li>

<li><a href="Information-theoretic_security" title="Information-theoretic security">Information-theoretic security</a></li>

<li><a href="Plaintext" title="Plaintext">Plaintext</a></li>

<li><a href="Codetext" class="mw-redirect" title="Codetext">Codetext</a></li>

<li><a href="Ciphertext" title="Ciphertext">Ciphertext</a></li>

<li><a href="Shared_secret" title="Shared secret">Shared secret</a></li>

<li><a href="Trapdoor_function" title="Trapdoor function">Trapdoor function</a></li>

<li><a href="Trusted_timestamping" title="Trusted timestamping">Trusted timestamping</a></li>

<li><a href="Key-based_routing" title="Key-based routing">Key-based routing</a></li>

<li><a href="Onion_routing" title="Onion routing">Onion routing</a></li>

<li><a href="Garlic_routing" title="Garlic routing">Garlic routing</a></li>

<li><a href="Kademlia" title="Kademlia">Kademlia</a></li>

<li><a href="Mix_network" title="Mix network">Mix network</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Mathematics</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Cryptographic_hash_function" title="Cryptographic hash function">Cryptographic hash function</a></li>

<li><a href="Block_cipher" title="Block cipher">Block cipher</a></li>

<li><a href="Stream_cipher" title="Stream cipher">Stream cipher</a></li>

<li><a href="Symmetric-key_algorithm" title="Symmetric-key algorithm">Symmetric-key algorithm</a></li>

<li><a href="Authenticated_encryption" title="Authenticated encryption">Authenticated encryption</a></li>

<li><a href="Public-key_cryptography" title="Public-key cryptography">Public-key cryptography</a></li>

<li><a href="Quantum_key_distribution" title="Quantum key distribution">Quantum key distribution</a></li>

<li><a href="Quantum_cryptography" title="Quantum cryptography">Quantum cryptography</a></li>

<li><a href="Post-quantum_cryptography" title="Post-quantum cryptography">Post-quantum cryptography</a></li>

<li><a href="Message_authentication_code" title="Message authentication code">Message authentication code</a></li>

<li><a href="Cryptographically_secure_pseudorandom_number_generator" title="Cryptographically secure pseudorandom number generator">Random numbers</a></li>

<li><a href="Steganography" title="Steganography">Steganography</a></li></ul>

</div></td></tr><tr><td class="navbox-abovebelow" colspan="2"><div>

<ul><li><span class="noviewer" typeof="mw:File"><span title="Category"></span></span> Category</li></ul>

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