AES, MD5, SHA1, DES are some common encryption theories that ppl use, they are not too hard to implement and they are pretty good as they are standarded by the government
you can probably just download the whole source of the encrypt/decrypt methods and use

but i still recommend writing ur own encryption method or do some manipulation on top of the encryption method u chose becoz for experienced crackers, they would no AES, MD5, SHA1, DES are pretty common and they would perform a brute force on the key using the decryption of each theory
u may make ur key a long one though then it will take crackers weeks to bruteforce it, but still eventually if u don't do any manipulation

but then again, if a cracker is willing to spent weeks to just bruteforce ur key, they can eventually crack it down in months even if u wrote ur own encryption
which is y internet activation is used, it may take them yrs to crack

Thx..
haha, for me its ok if they spend time to crack my program..
i just trying to learn some new stuff, the program will just take a week to write..
if they takes weeks to crack my program, seems not worth the effort

numbie, 不如講埋用ｉｎｔｅｒｎｅｔ　ａｃｔｉｖａｔｉｏｎ　要點做？
ｓｅｒｖｅｒ　同ｃｌｉｅｎｔ　兩邊要點做?
我對D networking 都係唔多識..