Editing Online codes (section)

===Inner encoding===
[[Image:online_codes_time_against_blocks_graph.png|frame|A graph of check blocks received against number of message blocks fixed for a 10000 block message.]]

The inner encoding takes the composite message and generates a stream of check blocks. A check block is the [[XOR]] of all the blocks from the composite message that it is attached to.

The ''degree'' of a check block is the number of blocks that it is attached to. The degree is determined by sampling a random distribution, ''p'', which is defined as:

:<math>F=\left\lceil\frac{\ln(\epsilon^2/4)}{\ln(1-\epsilon/2)}\right\rceil</math>

:<math>p_1=1-\frac{1+1/F}{1+\epsilon}</math>

:<math>p_i=\frac{(1-p_1)F}{(F-1)i(i-1)}</math> for <math>2\le i\le F</math>

Once the degree of the check block is known, the blocks from the composite message which it is attached to are chosen uniformly.