function y = crypto(x)% CRYPTO Cryptography example.% y = crypto(x) converts an ASCII text string into another, coded string.% The function is its own inverse, so crypto(crypto(x)) gives x back.% See also: ENCRYPT.% Use a two-character Hill cipher with arithmetic modulo 97, a prime.p = 97;% Choose two characters above ASCII 128 to expand set from 95 to 97.c1 = char(169);c2 = char(174);x(x==c1) = 127;x(x==c2) = 128;% Convert to integers mod p.x = mod(real(x-32),p);% Reshape into a matrix with 2 rows and floor(length(x)/2) columns.n = 2*floor(length(x)/2);X = reshape(x(1:n),2,n/2);% Encode with matrix multiplication modulo p.A = [71 2; 2 26];Y = mod(A*X,p);% Reshape into a single row.y = reshape(Y,1,n);% If length(x) is odd, encode the last character. if length(x) > n   y(n+1) = mod((p-1)*x(n+1),p);end% Convert to ASCII characters.y = char(y+32);y(y==127) = c1;y(y==128) = c2;