byte inversion in ciphertext

where k is the length of the ciphertext and n is a random number and i is an
integer denoting which character is bieng flipped. if i generate a number
such that n = a random number between 1 and k-1 such that n = rnd(k-1), then
passing through the ciphertext once and inverting every nth byte such that

for i = 1 to k
invert every nth byte
rof

where a byte inversion is the absolute value of the ascii code of a byte -
255 such that 0 inverted becomes 255, 1 inverted becomes 254 etc.

the attacker does not know the value of n and would therefore have to work
through the ciphertext trying every possible value of n and inverting every
n bytes before decryption.

being a rank amateur it seems to me that for large messages, this would
create a lot of work for an attacker, the larger the ciphertext the more
work required. the attacker can only know the length of the ciphertext and
the minimum and maximum value of n.

can someone tell me if the above outline for a fuction has any cryptographic
value at all, either on it's own or as part of a larger system.


.

Relevant Pages

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