The man is either a stupid fool or writer has it wrong. No encryption software exists today that the government cant break in a few days with their massively parallel arrayed decryption computers.
Maybe. But suppose all that's in there is random numbers: could a government that wanted to move against Assange be sure it was that, and not data that their decryption efforts had failed to read?
Wikipedia says this is the worlds current fastest computer:
In November 2009, the AMD Opteron-based Cray XT5 Jaguar at the Oak Ridge National Laboratory was announced as the fastest operational supercomputer, with a sustained processing rate of 1.759 PFLOPS. 
I’m sure somewhere the military has stuff that’s faster,
if not the same.