Ceaser's ciper is one of the simplest and most widely known encryption techniques.
It is a type of substitution cipher in which each letter in the plaintext is replaced by a letter some fixed number of positions down the alphabet.
For example, with a left shift of 3, D would be replaced by A, E would become B, and so on.
The method is named after Julius Caesar, who used it in his private correspondence.
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The Vigenère cipher (French pronunciation: [viʒnɛːʁ]) is a method of encrypting alphabetic text where each letter of the plaintext is encoded with a different Caesar cipher, whose increment is determined by the corresponding letter of another text, the key.
For example, if the plaintext is attacking tonight and the key is OCULORHINOLARINGOLOGY, then
the first letter a of the plaintext is shifted by 14 positions in the alphabet (because the first letter O of the key is the 14th letter of the alphabet, counting from zero), yielding o.
the second letter t is shifted by 2 (because the second letter C of the key means 2) yielding v.
the third letter t is shifted by 20 (U) yielding n, with wrap-around.
and so on; yielding the message ovnlqbpvt hznzouz.
If the recipient of the message knows the key, they can recover the plaintext by reversing this process.
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Bacon's cipher or the Baconian cipher is a method of steganographic message encoding devised by Francis Bacon in 1605.
A message is concealed in the presentation of text, rather than its content.
Baconian ciphers are categorized as both a substitution cipher (in plain code) and a concealment cipher (using the two typefaces).
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ROT13 cipher(read as – “rotate by 13 places”) is a special case of the Ceaser cipher in which the shift is always 13.
So every letter is shifted 13 places to encrypt or to decrypt the message.
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The Atbash cipher is a particular type of monoalphabetic cipher formed by taking the alphabet (or abjad, syllabary, etc.) and mapping it to its reverse, so that the first letter becomes the last letter, the second letter becomes the second to last letter, and so on.
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