16 byte key where each byte is in range 0-255, generated using cryptograhic PRNG will be believed to have 128 bit strength.
What would be a bit strength of a key generated using same quality PRNG, also of 16 byte length, if each byte instead of being one of 256 random values, would be one of 16 hexadecimal characters?
Would that be calculated as (128 x 16) / 256 = 8 bit?