HaiAll. we great to join this forum... would u help me to make this coding with VB net ? I have one task about substitution of plain text like this ABCD if I encrypt this word, will result DKUH description about it : key=3 (it is how many row) the length of plaint is 4, so 0 * 3 = ABCD 1 * 3 = DEFG 2 * 3 = KLM 3 * 3 = UV 4 * 3 = H so the result of cipher from ABCD is DKUH again, we encrypt this DKUH, this description like this : DKUH 1 * 3 GNXK 2 * 3 MTD 3 * 3 CV 4 * 3 H we will take the new result is HCDK this method above is some of cryptography algorithm (triangle chain). I very happy if you are should be help me to make this coding with using vb net. I use that for my paper... my full thank so.