A cryptocurrency (or crypto currency) is a digital asset designed to work as a medium of exchange that uses strong cryptography to secure financial transactions, control the creation of additional units, and verify the transfer of assets. Cryptocurrencies use decentralized control as opposed to centralized digital currency and central banking systems. The decentralized control of each cryptocurrency works through distributed ledger technology, typically a blockchain, that serves as a public financial transaction database.
When your Marja' has not issued a Fatwa (verdict) on a specific matter, you can refer to the second Marja' who is next highest in the degree of knowledge according to most senior Ulama of the Hawza.
Yes it is permissible to buy and sell like any other lawful businesses.
Yes it is permissible like any other business as far as it is real business and not gambling nor cheating in selling something which is not existing.
According to many of our leading scholars who studied the present financial market, it is allowed to deal in crypto currencies as far as it is real trade and not gambling or non existing imagination.
Bitcoin or any other crypto currency mining is permissible.
Cryptocurrency is one of those new issues that has some vagueness about it, both in terms of how it fits into understandings of shari'ah and also how it will fit into the world at large. Similar issues, in the past, were the emergence of cameras, credit cards, and democracy; it took time for there to develop both an understanding of the role they would play in the world, and also how to approach them from the angle of religious law. Only time will tell whether cyptocurrencies will eventually supplant state-regulated currencies in the way that digital bank accounts have, in many areas, supplanted cash, or state-regulated currencies supplanted things like coins with hard value (such as gold or silver).
Currently, due to the uncertainty regarding cryptocurrency, many (not all) scholars have approached the subject cautiously. Additional concerns include (a) the use of cryptocurrency for unlawful activities, (b) the illegality of cryptocurrency in some areas, and (c) the potential for harm/fraud.
Here is an article addressing fatwas from Shi'i scholars regarding Bitcoin, being the most common cyptocurrency: http://ijtihadnet.com/bitcoin-perspective-shiite-clerics-fatwas/
The answer of this question depends on the question on crypto currency itself whether it is real or not. Many of Muslim scholars are still not sure hence carrying on research on this matter. When the picture is clear for majority of the scholars, they will give their verdict on crypto currency.
You need to wait till this main question is answered, then the question of brokerage comes after that.
Sayyed Sistani: According to obligatory precaution one must refrain from these transactions (i.e. you can refer to the second most knowledgeable jurist and follow his opinion).
Sayyed Khamenei: No response (i.e. you can refer to the second most knowledgeable jurist and follow his opinion).
It should be noted that in his opinion, it is necessary to observe the official laws of the country in this regard.
Sayyed Shobeiri Zanjani: If the use of such currencies is usually corrupt or illegal from an economical point of view, there is a problem with buying and selling them. (meaning according to obligatory precaution one must refrain from these transactions i.e. you can refer to the second most knowledgeable jurist and follow his opinion)
Sheikh Makarem Shirazi: Due to the many ambiguities that Bitcoin has, it is problematic (meaning according to obligatory precaution one must refrain from these transactions i.e. you can refer to the second most knowledgeable jurist and follow his opinion.)
Sheikh Vahid Khorasani: Buying and selling it is void.
Sheikh Saffi Golpayegani: It's forbidden and it's a type of eating up wrongfully. Allah is the All-Knowing
Sheikh Noori Hamedani: Engaging in these transactions is problematic (i.e. you can refer to the second most knowledgeable jurist and follow his opinion.)
Sheikh Hadavi Tehrani: Buying and selling Bitcoin is Haraam and as for other cryptocurrencies which do not have the problems of Bitcoin, it is permissible. (So his Fatwa about other cryptocurrencies is conditional to not having the problems of Bitcoin)
If you mean that the company rewards you with more tokens if you do more business with them or vote for them or bring more customers, then this reward is allowed
for you. This is when the activities of the company is investing in lawful business only.
Buying and selling Bitcoins and other crypto currencies is allowed just like buying and selling any other coin.
It is allowed to invest in stocks, bonds, mutual funds , cryptocurrancy . etc, but it is not allowed to invest in any share of a company which does unlawful investment or work, like alcohol, un Islamic banks, etc
According to Ayatullah Sistani, Muslims are not allowed to violate the law of Non Muslim countries after committing to abide it during applying for Visa or Stay Permit etc. Obviously, the law should not violate Islamic rules.