MelissaA
Brenton
Shilpa Karhik
Substitution Ciphers Part 2
June 8th 2006 05:23
Well, here are the two final types of simple substitution ciphers, tomorrow I will deal with the objections to the Turing Test.
Polyalphabetic Substitution
This used multiple cipher alphabets to translate the one alphabet and had a number of ways of choosing which alphabet to use. So a system with two alphabets could be:
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
Z Y X W V U T S R Q P O N M L K J I H G F E D C B A
M L K J I H G F E D C B A Z Y X W V U T S R Q P O N
And a number could be placed in front of the message to say which alphabt is used. So Adam could be 1ZWZN or 2MJMA.
Polygraphic Substituions
These substitute one ciphertext letter for 2 (or more) plaintext letters. A simple system would be like that below. In this the word BE would be translated as J. Of course, this system would be too complicated for an alphabet of 26 letters, but systems have been designed to get around this.
This system is harder to crack with frequency tests.
Well there we go, there is an outline of some simple substitution ciphers.
Adam
Polyalphabetic Substitution
This used multiple cipher alphabets to translate the one alphabet and had a number of ways of choosing which alphabet to use. So a system with two alphabets could be:
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
Z Y X W V U T S R Q P O N M L K J I H G F E D C B A
M L K J I H G F E D C B A Z Y X W V U T S R Q P O N
And a number could be placed in front of the message to say which alphabt is used. So Adam could be 1ZWZN or 2MJMA.
Polygraphic Substituions
These substitute one ciphertext letter for 2 (or more) plaintext letters. A simple system would be like that below. In this the word BE would be translated as J. Of course, this system would be too complicated for an alphabet of 26 letters, but systems have been designed to get around this.
Polygraphic Substitution
This system is harder to crack with frequency tests.
Well there we go, there is an outline of some simple substitution ciphers.
Adam
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