how to encode a bit sequences with key?

how to encode bit sequences with a key, before embedded into an images ( to enhance the secure) , then extracted and decode with this key to return the first sequences.

Answer 1

[Walter Roberson]

nK = 17;  %for example, length of key
key_sequence = round(rand(1,nK));  %example key

nB = 50;  %for example, length of bit sequence
bit_sequence = round(rand(1,nB));   %example bits

new_bits = zeros(1, nB);
for J = 1 : nB
  new_bits(J) = xor( bit_sequence(J), key_sequence(mod(J-1, nK)+1) ); %xor with key
end