When blocks are encrypted in chains, the substitution phase of the first subround is suppressed for the first block of the chain to be encrypted. In encryption of single blocks (1-chains) this first substitution phase is always suppressed. This initial substitution phase is suppressed to limit the degree to which the content of the link can be inferred by its action on chosen plaintext. In the production of a chain, this is only a potential danger for the first block in the chain.
The structure of CA-1.0 allows an infinite number of blocks to be linked
together in a chain. As more blocks are chained together the random initial
link information is distributed across all of the blocks. This has the
advantage of reducing the data-expansion rate. Long chains have two
potential disadvantages, however:
1) an error anywhere during the transmission of the chain
could garble the entire chain, and 2) excessive dilution
of the link randomness could
weaken the security of the system. For these reasons chains are limited
to no more than 100 blocks using CA-1.0. For chains of 100 blocks the
data-expansion rate is 
.