since Porta cipher use several alphabets, its index will obviously be low. It is possible to recognize a Porta encrypted cipher by analyzing Is long enough and if the encrypted text isn't too long (to avoid easy frequency analysis). However it is admitted that Porta cipher is still secure if the key length He just used a simple frequency analysis after he founds the key length (thanks to Friedman test). Remained secure until the Cryptologist Kasiski managed to break it back in 1863. It usually needs the encryption key and the alphabets that were used. Join Facebook to connect with Giovanni Giovanni Prota and others you may know. To decrypt Porta cipher, you just have to reverse this process. View the profiles of people named Giovanni Giovanni Prota. For the letter "o", we check in the alphabet "EF" and we see that the encrypted letter for "o" is "d", and so on. For instance to encrypt the first letter, "p", with the key letter "k", we look into the "KL" alphabetĪnd we see that the counterpart to "p" is "h". Then we look for each letter to encrypt, its counterpart in theĪlphabet indicated by the key letter we are using. We want to encrypt the sequence "Porta cipher" using the key "key":Ĭ h i f f r e d e P o r t a c l e c l e c l e c l e c l o p t r n g q y p d g g h vĪs you can see, we reapeat the key as many as it's necessary to match the text length. As this is hard to explain with words, here's an example :ĪB 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 CD a b c d e f g h i j k l m z n o p q r s t u v w x y EF a b c d e f g h i j k l m y z n o p q r s t u v w x GH a b c d e f g h i j k l m x y z n o p q r s t u v w IJ a b c d e f g h i j k l m w x y z n o p q r s t u v KL a b c d e f g h i j k l m v w x y z n o p q r s t u MN a b c d e f g h i j k l m u v w x y z n o p q r s t OP a b c d e f g h i j k l m t u v w x y z n o p q r s QR a b c d e f g h i j k l m s t u v w x y z n o p q r ST a b c d e f g h i j k l m r s t u v w x y z n o p q UV a b c d e f g h i j k l m q r s t u v w x y z n o p WX a b c d e f g h i j k l m p q r s t u v w x y z n o YZ 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 nFor fully understanding Porta cipher, let's see the example above. When you want to encrypt a text, using a key, you check the corresponding letter in the alphabet corresponding Simplicity here, we'll use the "normal" alphabets. But Porta himself said that it would be more secure to use random alphabets, and carry them to decipher crypted texts. As you can see in the table, these alphabets are easy to makeįrom scratch. Since there is 13 couples of letters in the latinĪlphabet, there is also 13 alphabets (AB, CD, EF, GH, IJ, KL, MN, OP, QR, ST, UV, WX, YZ). Each couple of letter in the alphabet has its own alphabet. The cipher principle is simple, but secure. The Porta cipher was used for three centuries (up to the 19th century). This makes the Porta cipher really secure in comparison to This cipher was the first one to use multiple alphabets and change it for each letter to encrypt. Porta cipher is a polyalphabetical cipher which was created by an Italian physicist named Giovanni Battista Della Porta, back in 1563.
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