cryptography - Which encryption mode ECB, CBC, CFB -

My php script and my C # application will pass the hash string for each other, which is 32 characters long, the best approach What is it for? I thought the ECB but as an uncertain, it says that if you do not use 1 block, do not use it. How do I know how big the block is?

They will sometimes pass a large text file, which would be the best way to encrypt it ... CBC?

Any useful welcome ...

thanks

ECB is the easiest way and not really

Personally I use CBC.