Now let's do some real maths.
If you have 16Byte keys the real number of combinations is 256^16 since each Byte can have 256 different values. Another way to think of it is 16Bytes equals 128bits, since each bit can have 2 different values the number of combinations is 2^128.
Either way, they both come up with the same result:
256^16 = 3.4x10^38
2^128 = 3.4x10^38
So just how big is this number?
Approximately 340,282,366,920,938,463,463,374,607,431,770,000,00 0.
To put things in perspective, the current generally accepted age of the universe is 13.7 billion years. In nanoseconds that is 4.3x10^26.
That is 430,000,000,000,000,000,000,000,000.
Now imagine you could check a combination each nanosecond (which you couldnt: assuming it takes one cycle to execute each instruction on the psp, it actually takes a few cycles, even running at 333MHz would take around 3ns to execute each instruction).
So if you started from the begininning of creation and checked one combination each nanosecond until the present day, you would have only bruteforced a little over 88 bits, thats 11 bytes !
If you're unable to comprehend the math used above, just know it would take several billion years with our current technology to bruteforce the encryption unless something gets leaked from Sony.