if you want to encrypt the file *securely*
Heres a little theory/tutorial for EASY encryption and incredibly hard decryption (for hackers).
//----------------------------------------------------------------------------
GCC MATH IS GREAT
= 0
a = 1
b = 2
c = 3
d = 4
e = 5
f = 6
g = 7
h = 8
i = 9
j = 10
k = 11
l = 12
m = 13
n = 14
o = 15
p = 16
q = 17
r = 18
s = 19
t = 20
u = 21
v = 22
w = 23
x = 24
y = 25
z = 26
message (dimension arbitrary) = [M]
[(7 3 3)
(0 13 1)
(20 8 0)
(9 19 0)
(7 18 5)
(1 20 0)]
encoder = [E]
[(1 -2 2)
(-1 1 3)
(1 -1 -4)]
coded = [M]*[E] = [C]
[(7 -14 11)
(-12 12 35)
(12 -32 64)
(-10 1 75)
(-6 -1 48)
(-19 18 62)]
decoder = [E]^-1
[(-1 -10 -8)
(-1 -6 -5)
(0 -1 -1)]
decoded = [M]*[E]*[E]^-1 = [C]*[E]^-1 => [M]*[I] = [C]*[E]^-1 => [M] = [C]*[E]^-1
[(7 3 3)
(0 13 1)
(20 8 0)
(9 19 0)
(7 18 5)
(1 20 0)]
//------------------------------------------------------------------------------
Your message matrix determines your encryption matrix, specifficaly the COLUMNS (vertical). If your message matrix is 2x6 then your encryption matrix would be a 6x6 matrix.
Keep in mind the larger your encryption matrix is, the less likely it can be brute forced. Also, use Sparse number in odd ranges, 1 -235 3000000000 888 are good ranges, while 1 3 9 and 7 would be likely to be found in a brute force program.
Also note that you encryption matrix MUST, i repeat MUST have an inverse matrix, to check, get out a graphing calculator, enter the matrix and press inverse key followed by enter and copy that down.