By using less different block lengths, a hexagonally-packed-cylinder geometry can be obtained.

In the case of modern block ciphers, they use a 128-bit block length.

But, it was shown that varying randomly the block length can avoid this problem.

The outer code have the relative distance and block length of .

In practical situations, there are limitations to the delay of the communication and the block length must be finite.

Therefore it is important to study how the probability of error drops as the block length go to infinity.

You can actually implement Rijndael in a block length that's any multiple of 32 bits.

So the standard was set at 128-bit block length.

Let be the block length, two different constants of size .

The rate of is its dimension divided by its block length.