I think the crypto-algorithm is chosen by ftp server.
168bit cipher is 3DES, a mode of the DES encryption algorithm that encrypts data three times. Three 56-bit keys are used, instead of one, for an overall key length of 168 bits.
Personally, I trust 3DES algorithm instead of AES. Because DES/3DES is an "old" cipher. It has been studied thoroughly for decades. And there is no attacks have been found against 3DES yet.
Detail info:
http://kingkong.me.berkeley.edu/~ken...ms250/des.html
sorry for my bad english..