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Diffstat (limited to '3544/DEPENDENCIES/Chapter_2.sci')
| -rw-r--r-- | 3544/DEPENDENCIES/Chapter_2.sci | 274 |
1 files changed, 274 insertions, 0 deletions
diff --git a/3544/DEPENDENCIES/Chapter_2.sci b/3544/DEPENDENCIES/Chapter_2.sci new file mode 100644 index 000000000..3ec8f93e0 --- /dev/null +++ b/3544/DEPENDENCIES/Chapter_2.sci @@ -0,0 +1,274 @@ +
+//////////////////////////////////////
+// Caesar cipher //
+//////////////////////////////////////
+
+
+//Generalised Caesar cipher encryption
+function [ct] = encrypt_caesar_general(pt,key)
+ a = ascii('A')
+ l = length(pt)
+ ct = zeros(l)
+
+ for i =1:l
+ if isletter(part(pt,i:i)) then
+ ct(i) = a + modulo( ascii(part(pt,i:i))+key-a, 26 )
+ else
+ ct(i) = ascii( part(pt,i:i) )
+ end
+ end
+ ct = char(ct)
+ ct = strcat(ct)
+endfunction
+
+//Caesar cipher encryption (key = 3 always)
+function [ct] = encrypt_caesar(pt)
+ ct = encrypt_caesar_general(pt,3)
+endfunction
+
+
+//Generalised Caesar cipher decryption
+function [pt] = decrypt_caesar_general(ct,key)
+ a = ascii('A')
+ key = 26-key
+ l = length(ct)
+ pt = zeros(l)
+
+ for i =1:l
+ if isletter(part(ct,i:i)) then
+ pt(i) = a + modulo( ascii(part(ct,i:i))+key-a, 26 )
+ else
+ pt(i) = ascii(part(ct,i:i));
+ end
+ end
+ pt = char(pt)
+ pt = strcat(pt)
+endfunction
+
+
+//Caesar cipher decryption (key = 3 always)
+function [pt] = decrypt_caesar(ct)
+ pt = decrypt_caesar_general(ct,3)
+endfunction
+
+
+
+//////////////////////////////////////
+// Playfair cipher //
+//////////////////////////////////////
+
+
+
+//func to remove spaces from a string
+function [mat]=remove_spaces(str)
+ mat=[]
+ k=1
+ for i=1:length(str)
+ if ~isletter(part(str,i:i)) then
+ continue
+ end
+ mat(k,1) = part(str,i:i)
+ k=k+1
+ end
+ mat = strcat(mat)
+endfunction
+
+
+//func to substitute I for J
+function [mat]=i_to_j(str)
+ str = remove_spaces(str)
+ mat=[]
+ k=1
+ for i=1:length(str)
+ mat(k,1) = part(str,i:i)
+ if mat(k,1)=='J' then
+ mat(k,1) = 'I'
+ end
+ k = k+1
+ end
+ mat = strcat(mat)
+endfunction
+
+//func to insert X between repeating characters
+function [mat]=handle_duplicates(str)
+ mat = []
+ l = length(str)
+ k = 1
+
+ for i=1:l
+ if i>1 & part(str,i:i)==part(str,i-1:i-1) then
+ mat(k,1)='X'
+ k=k+1
+ end
+ mat(k,1) = part(str,i:i)
+ k = k+1
+ end
+ mat = strcat(mat)
+endfunction
+
+//Matrix creation and population for Playfair cipher
+//func to populate playfair matrix
+function [mat]=playfair_matrix(key)
+
+ key = i_to_j(key)
+ a = ascii('A')
+ i = ascii('I')
+ j = ascii('J')
+ row = 5
+ col = 5
+ visited = zeros(26,1);
+ mat = ones(row,col);
+
+ len = length(key)
+
+ li=1
+ k=1
+
+ for m=1:row
+ for n=1:col
+ while li<=len & visited(ascii(part(key,li:li)) - ascii('A')+1,1)~=0,
+ li=li+1
+ if part(key,li:li)=='I' & visited(j-a+1)==1 | part(key,li:li)=='J' & visited(i-a+1)==1 then
+ li = li+1
+ end
+ end
+ while k<=26 & visited(k,1)~=0
+ k=k+1
+ if k==i-a+1 & visited(j-a+1)==1 | k==j-a+1 & visited(i-a+1)==1 then
+ k = k+1
+ end
+ end
+ if li<=len then
+ mat(m,n) = ascii(part(key,li:li))
+ visited(ascii(part(key,li:li))-a+1,1) = 1
+ else
+ mat(m,n) = k+ascii('A')-1
+ visited(k,1) = 1
+ end
+
+ end
+ end
+
+endfunction
+
+//func to check and convert plaintext to suitable format for encipherment using playfair cipher
+function [mat]=playfair_pt(pt)
+ mat = i_to_j(pt)
+ mat = handle_duplicates(mat)
+endfunction
+
+function [mat]=digram_array(pt)
+ k = 1
+ l = length(pt)
+ for i=1:l
+ if modulo(i,2)==0 then
+ continue
+ end
+ mat(k,1) = part(pt,i:i)
+ i=i+1
+ if i>l then
+ mat(k,2) = 'X'
+ else
+ mat(k,2) = part(pt,i:i)
+ end
+ k=k+1
+ end
+endfunction
+
+function []=print_matrix(mat,new_line)
+ [r,c] = size(mat)
+ t = type(mat)
+
+ for i=1:r
+ for j=1:c
+ if t==[1] then // real numbers return 1, characters return 10
+ printf("%c ",ascii(mat(i,j)))
+ else
+ printf("%c ",mat(i,j))
+ end
+ end
+ printf(" ")
+ if new_line~=0 then
+ printf("\n")
+ end
+ end
+endfunction
+
+function [r,c]=find_letter(key_mat,a)
+ [row,col] = size(key_mat)
+ r = 0
+ c = 0
+ for i=1:row
+ for j=1:col
+ if ascii(key_mat(i,j))==a then
+ r=i
+ c=j
+ break
+ end
+ end
+ end
+endfunction
+
+
+function [mat]=encrypt_playfair(pt_mat,key_mat)
+
+ [row,col] = size(pt_mat)
+ mat = []
+
+ for i=1:row
+ a = pt_mat(i,1)
+ b = pt_mat(i,2)
+ [r_a,c_a] = find_letter(key_mat,a)
+ [r_b,c_b] = find_letter(key_mat,b)
+
+ if r_a==r_b then
+ c_a = modulo(c_a,5)+1
+ c_b = modulo(c_b,5)+1
+ elseif c_a==c_b then
+ r_a = modulo(r_a,5)+1
+ r_b = modulo(r_b,5)+1
+ else
+ temp = c_a
+ c_a = c_b
+ c_b = temp
+ end
+ mat(i,1) = ascii(key_mat(r_a,c_a))
+ mat(i,2) = ascii(key_mat(r_b,c_b))
+
+ end
+endfunction
+
+
+//////////////////////////////////////
+// Transposition cipher //
+//////////////////////////////////////
+
+function [mat]=message_rectangle(str,col)
+ l = length(str)
+ row = l/6
+ if modulo(l,6)>0 then
+ row=row+1
+ end
+ //remove whitespace and non-alphabets from string
+ str = remove_spaces(str)
+ //Conversion of plaintext into a message table
+ mat = []
+ k=1
+ for i=1:row
+ for j=1:col
+ if k>l then
+ break
+ end
+ mat(i,j) = part(str,k:k)
+ k=k+1
+ end
+ end
+endfunction
+
+//////////////////////////////////////
+// Diffie-Hellman Key Exchange //
+//////////////////////////////////////
+
+function [key]=diffie_key(g,p,n)
+ key = modulo(g^p,n)
+endfunction
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