Cipher $($cipher$.$py$)$ Atbash Cipher $$ is a substitution cipher where the encrypted message is

obtained by looking up each letter and finding the corresponding letter in a reversed alphabet.

The encoded letter can be found in one of two ways, either a parallel list look up $($ex$.$ letter to

encode $=$B$,$ location $=1,$ encoded letter location $=1,$ which is a $$Y$),$ or a calculated position

in the list $($ex$.$ letter to encode $=$B$,$ location $=1,25$ location $=24,$ encoded letter location $=$

$24,$ which is a $$Y$).$

$012345678910111213141516171819202122232425$

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

$1.\_\_$init$\_\_($self$)$ initializes the alphabet attribute $$ make a list with the letters A$-$Z in it

$($alternatively$,$ make a string with letters A$-$Z in it$,$ since a string is a list of characters$).$

$2.$ encrypt$\_$message$($self$,$ message$)$ pass in the message string. Convert the message

to upper case letters, then loop through the message string one character at a time, if it is

a letter A$-$Z$,$ then call the encrypt$\_$letter method, otherwise ignore the character. Build

the encryption string using the encrypted letters and ignored characters, and then return it

$($ie$.$ leave all spaces, punctuation, and numbers the same, only letters in the string will be

encrypted$).$

$3.$ decrypt$\_$message$($self$,$ message$)$ pass in the message string. Convert the message

to upper case letters, then loop through the message string one character at a time. Build

the decryption string using the decrypted letters in a manner similar to the

encrypt$\_$message method above.

$2024$ Cleary

$4.\_$encrypt$\_$letter$($self$,$ letter$)$ passes in one character, letter. Look up the letter

in the alphabet to find its location. Use that location to calculate the position of the

encrypted letter in the manner described above, then return the encrypted letter.

$5.\_$decrypt$\_$letter$($self$,$ letter$)$ passes in one character, letter. Look up the letter

in the alphabet to find its location. Use that location to calculate the position of the

decrypted letter in the manner described above, then return the decrypted letter.

Casesar $($caesar$.$py$)$ Caesar Cipher $$ this is another substitution cipher where the encrypted

message is found by looking up each letter and finding the corresponding letter in a shifted

alphabet $($ex$.$ letter to encode $=$B$,$ location $=1,$ shift value $=3,$ location $+$ shift value $=1+3=$

$4,$ encoded letter location $=4,$ which is an $$E$).$ If the shift value causes the encoded letter to be

past the end of the alphabet, then it should wrap around to the beginning $($ex$.$ letter to encode $=$

$$X$,$ location $=23,$ shift value $=3,$ location $+$ shift value $=23+3=26,$ encoded letter location $=$

$26,$ which is larger than $25,$ subtract the total number of letters in the alphabet to get the updated

location, $2626=0,$ which is an $$A$).$

Example alphabet with a shift value of $3$:

$012345678910111213141516171819202122232425$

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

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

$1.$ Extend the Cipher class.

$2.\_\_$init$\_\_($self$,$ shift$)$ passes in caesar cipher$$s shift value. Call super to initialize

the alphabet, then set the shift value.

$3.\_$encrypt$\_$letter$($self$,$ letter$)$ overridden method $$ passes in one character,

letter. Look up the letter in the alphabet to find its location. Use that location to calculate

the position of the encrypted letter in the manner described above, then return the