# Create a vigenere cipher encryption

I have a question about the Vigenere cipher and still do not know how to solve it.

A language has an alphabet of only 4 letters with frequencies as follow: Pa=40%, Pb=20%, Pc=10% and Pd=30%. Create an encryption function from this alphabet {a,b,c,d} into the set of numbers 0-9 so that IC of cyphertexts created by this encryption scheme is minimum. Explain your idea. My idea is: For Vigenere, the letter frequencies becomes more equally for higher key length -> IC become lower so to get minimum IC i think we can encrypt characters like this: a: 40% -> {0,1,2,3}, b:20% -> {4,5}, c:10% -> {6}, d:30% -> {7,8,9}

• While we can help with homework questions, we require that you have at least tried to solve it yourself. Dec 8 '21 at 10:49
• My solution is: For Vigenere, the letter frequencies becomes more equally for higher key length -> IC become lower so to get minimum IC i think we can encrypt characters like this: a: 40% -> {0,1,2,3}, b:20% -> {4,5}, c:10% -> {6}, d:30% -> {7,8,9} Dec 8 '21 at 14:46
• Please edit your question to include these details. Dec 8 '21 at 17:00