the SPI flash size of all pine boards is 128Mbits or 16MBs. it is intended for using as a firmware home, - uboot in this case, and not everything else. it's small for general usage, it wears out for frequent read/write cycles, and it gives you no advantage of having your cryptographic keys there. it is storage for firmware. there is nothing "unreliable " in it. this whole thread became a mess of confusions.
ANT - my hobby OS for x86 and ARM.