stream ciphers and realtime communications?

[Bruce Schneier]

Stream ciphers are very efficient in hardware encryption applications, but
suck eggs in software.  They have been the workhorse of military cryptography
for at least 40 years, but those are all hardware applications.  If you
are working in software, it is much easier to deal with data in 64-bit
blocks than in individual bits.  The Shrinking Generator, which has only
two LFSRs, is slower than DES in software.  You need to iterate the
Shrinking Generator 64 times to encrypt the data that DES handles in just
one iteration.

Bruce