1 files changed, 55 insertions, 0 deletions
diff --git a/3544/CH2/EX2.42/Ex2_42.sce b/3544/CH2/EX2.42/Ex2_42.sce
new file mode 100644
index 000000000..8281e7a56
--- /dev/null
+++ b/3544/CH2/EX2.42/Ex2_42.sce
@@ -0,0 +1,55 @@
+//Vernam cipher
+
+// Move scilab to current file directory
+[u,t,n] = file()
+n = strcat(n)
+file_name = basename(n)+fileext(n)
+file_name = strcat(file_name)
+ind=strindex(n,file_name)
+path = part(n,1:ind-1)
+chdir(path)
+
+exec("Chapter_2.sci",-1)
+
+a= ascii('A')
+
+pt = "HOW ARE YOU?"                 //Plaintext
+disp("")
+disp("Original plaintext:")
+disp(pt)
+
+//function from dependency file
+pt = remove_spaces(pt)              //Processed plaintext for encryption
+
+disp("")
+disp("Plaintext:")
+disp(pt)
+disp(ascii(pt)-a)
+
+disp("")
+disp("One-time pad:")               
+otp = "NCBTZQARX"                   //OTP
+disp(otp)
+disp(ascii(otp)-a)
+
+ct = []
+
+for i=1:length(pt)                  //Encryption stage
+    ct(i) = ascii(part(pt,i:i)) + ascii(part(otp,i:i)) -2*a
+end
+
+disp("")
+disp("Initial total:")
+disp(ct')
+
+
+disp("")
+disp("Subtracting 26 if >25")
+ct = modulo(ct,26)                  //Taking modulo 26 to make range b/w 0-25
+disp(ct')
+ct = char(ct+a)'                    //Ciphertext
+
+disp("")
+disp("Ciphertext: ")
+disp(strcat(ct))                
+