Wolfram Function Repository

Instant-use add-on functions for the Wolfram Language

Function Repository Resource:

 AffineCipher

Source Notebook

Encipher a string using the affine cipher

Contributed by: Sander Huisman

ResourceFunction["AffineCipher"][string,{a,b}]

enciphers string using the affine cipher with parameters a and b.

ResourceFunction["AffineCipher"][{a,b}]

represents an operator form of ResourceFunction["AffineCipher"] that can be applied to an expression.

Details and Options

For the affine cipher, the letters "a"–"z" are numbered 0–25. Each character in string is converted to a number x using the aforementioned numbering. Each number is then transformed by computing (ax+b)mod26. The new numbers are then reinterpreted as letters.
Here is an example enciphering the letters "A"–"Z" for a=5 and b=8. Deciphering is done by reading the diagram from bottom to top.
The case of the letters is retained by ResourceFunction["AffineCipher"].

Examples

Basic Examples (1) 

Convert a simple text:

In[1]:=
ResourceFunction["AffineCipher"]["affine cipher", {5, 8}]
Out[1]=

Scope (2) 

AffineCipher automatically threads over a list of strings:

In[2]:=
ResourceFunction["AffineCipher"][{"this", "is", "a", "test"}, {5, 8}]
Out[2]=

Create an operator:

In[3]:=
op = ResourceFunction["AffineCipher"][{5, 8}]
Out[3]=

Apply the operator to a string:

In[4]:=
op["balloon"]
Out[4]=

Properties and Relations (1) 

The Caesar cipher can be recreated using the affine cipher by choosing a=1:

In[5]:=
string = "This is just a test"; {ResourceFunction["AffineCipher"][string, {1, 8}], ResourceFunction["CaesarCipher"][string, 8]}
Out[5]=

Possible Issues (2) 

The parameter a must be coprime with 26:

In[6]:=
ResourceFunction["AffineCipher"]["Mathematica", {4, 2}]
Out[6]=

Some of the permissible values for a are:

In[7]:=
Select[Range[100], CoprimeQ[#, 26] &]
Out[7]=

Strings using numbers or letters with diacritics are not converted:

In[8]:=
ResourceFunction[ "AffineCipher"]["It was Chloë who opened the 2 piñatas", {5, 8}]
Out[8]=

Use RemoveDiacritics, StringDelete, IntegerName and ToLowerCase to transform the message:

In[9]:=
string = StringReplace[ ToLowerCase[ StringDelete[ RemoveDiacritics["It was Chloë who opened the 2 piñatas"], " "]], r : Longest[DigitCharacter ..] :> IntegerName[ToExpression@r]]
Out[9]=

Now the transformed message can be enciphered:

In[10]:=
ResourceFunction["AffineCipher"][string, {5, 8}]
Out[10]=

Publisher

SHuisman

Version History

  • 1.0.0 – 07 August 2019

Related Resources

License Information