mode of operation in cryptography We need to choose a mode of operation for a Telnet like application where the average message size is between 7 and 1024 bytes. What is the best mode of operation in this case?

a.  CBC
b.  CFB
c.  CTR
d.  Any of the above is ok
I would pick e) none of the above. None of those modes offers integrity protection, so unless integrity is handled elsewhere, your application is wildly insecure. An attacker could modify bits in transit and do nefarious things.

Of the three, CFB and CTR are the worst for the application and should be very easy for an attacker to mount successful attacks, changing commands being sent to the server that are properly formatted. CBC would take a little more creativity, but shouldn't be too hard for an intelligent attacker.