Speed Accuracy 1 second 3200 bits 8848 bits 19712 bits 1bit/s 99,82% 0.5 seconds 2400 bits 8142 bits 18123 bits 2 bit/s 99,5% • C-based implementation in the first threat model • ETag contains mtime (last modified time with microsecond accuracy), so theoretical channel capacity is bigger than its practically possible one. • Maximum practical speed of the covert channels is about 1 bit per (2L+T) seconds, where L is HTTP latency between u2 and s1 and T is a time that is needed for auxiliary operations Experiment 2