What are the advantages of using OFB (Output Feedback Mode)? I have a problem with OFB mode, because I have heard that it is stronger than CFB.
I have a problem with OFB mode, because I have heard that it is stronger than CFB.


On the contrary I would say that CFB is stronger.

OFB means encrypting the IV again and again to produce the keystream. If you end up in a cycle, the keystream will start repeating itself. (This should not be a practical weakness, but why chance it?)

CFB is more like CBC, in that it uses the ciphertext as input to the cipher for the next block. This means it will not enter cycles unless e.g. encrypting a constant plaintext. CFB can also recover from IV reuse if the plaintext it different (which is an advantage even over CTR).


  What are the advantages of using OFB (Output Feedback Mode)?


One advantage OFB does have over CFB is that you can pregenerate the keystream, since it does not depend on the plaintext. However, as the other answer states, encryption with either algorithm is serial and cannot be parallelized. That makes CTR the best choice for performance, since it also allows keystream pregeneration.

Of course, in the real world you should just use an authenticated encryption mode (like GCM) unless you are certain you know what you are doing.