Example. The Caesar method receives a string value and an int that indicates the shift. In the method, we convert the string to a char array with ToCharArray.
Info We can see that this cipher is reversible. A call to Caesar(string, 18) can be reversed with a call to Caesar(string, -18).
Also The example from Wikipedia can be solved with a call to Caesar(string, -4).
using System;
class Program
{
/// <summary>/// Apply Caesar cipher with shift./// </summary>
static string Caesar(string value, int shift)
{
char[] buffer = value.ToCharArray();
for (int i = 0; i < buffer.Length; i++)
{
// Letter.
char letter = buffer[i];
// Add shift to all.
letter = (char)(letter + shift);
// Subtract 26 if past z.// ... Add 26 if below a.
if (letter > 'z')
{
letter = (char)(letter - 26);
}
else if (letter < 'a')
{
letter = (char)(letter + 26);
}
// Store.
buffer[i] = letter;
}
return new string(buffer);
}
static void Main()
{
string a = "test";
string b = Caesar(a, 18); // Ok
string c = Caesar(b, -18); // Ok
string d = Caesar(a, 1); // Ok
string e = Caesar(d, -1); // Ok
string f = "exxegoexsrgi";
string g = Caesar(f, -4); // Ok
Console.WriteLine(a);
Console.WriteLine(b);
Console.WriteLine(c);
Console.WriteLine(d);
Console.WriteLine(e);
Console.WriteLine(f);
Console.WriteLine(g);
}
}test
lwkl
test
uftu
test
exxegoexsrgi
attackatonce
Numeric characters. What happens with non-letter characters in the cipher? The cipher does not specify how numbers should be treated. It would be simple to ignore them.
Also Another option would be to throw an exception if a number is found. Callers of Caesar would have to be prepared for this.
Summary. The Caesar cipher is a substitution cipher that shifts letter positions. It is similar to ROT13. The shift value can be kept secret to make the cipher harder to break.
A final note. This sort of cipher will not provide any real security. You could use the Caesar cipher and then an actual encryption algorithm on top of that.
Dot Net Perls is a collection of pages with code examples, which are updated to stay current. Programming is an art, and it can be learned from examples.
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This page was last updated on Sep 15, 2022 (grammar).