https://lmgtfy.com/?q=china+icloud+encryption+keys
You could also look at some of the other links already posted to this thread in response to similar queries from you and others, like this one (https://news.ycombinator.com/item?id=21207931) and this one (https://news.ycombinator.com/item?id=21208376).
Tianhe-2 Supercomputer @ 33.86 petaflops (quadrillion flops)
=33 860 000 000 000 000 keys per second (33.86 quadrilion)
3.386e16 * 31556952 seconds in a year 2255 possible keys
2^255 / 1.0685184e24
=1.0685184e24 keys per year (~1 septillion, 1 yottaflop)
=5.4183479e52 years
Needless to say, that's a long fucking time. Yes, cracking an access password would be much less time-consuming and so would finding and using non-brute force attack methods to guess or steal the key but for your basic claim that "Yes", China has cracked strong encryption, I just don't see where you get that idea from.