Need to be replaced on `.copy`: https://github.com/cryptocoinjs/drbg.js/blob/4dc077f2c87bccaf0092f949d6c8cbfdc33e658d/hash.js#L85 https://github.com/cryptocoinjs/drbg.js/blob/4dc077f2c87bccaf0092f949d6c8cbfdc33e658d/hmac.js#L63
