if the motive of the bitcoin owner is for obvious speculation it is prohibited in Islam, for example is altcoin trading in the exchanger, not just speculative motives in bitcoin trading, in other speculations also should not, for example is stock trading whose time is not too far between buying and sell, if the main motive is for investment, then my knowledge is allowed. for example, people store bitcoin or other coins in a long time to invest for funds that he used better then it is okay, so also with stocks, if the person is speculating then the law should not