急!!求加密解密一文當(用turbo2.0)&文件字符轉換

[piziliu2003]

我有一文件dmi.txt如下所示, 我想把其內容加密,然後解密.
我只要求轉化一下ascii碼來改變字符就行. (麻煩高手提供源代碼)急用.!!謝謝
還有如果我想把 dmi.txt文件的第四行的LANCE轉變為小寫然後保存..怎麼用代碼實現

dmi.txt內容


DMI (R.21.3.6)

Manufacturer :"NEC "
Model :"LANCE "
Version :" "
Serial :"SN-123456UVXV2I8B5O6N1N1K "
1234567890123456789012345678901234567890
UUID :00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

Manufacturer :"NEC "
Model :"Lance"
Version :"0.3C"
Serial :"NF3B08278"
1234567890123456789012345678901234567890

Manufacturer :"NEC