I am aware of the existing, similar questions, and I have read them and found them valuable. However, I do not feel as if I have truly got a conclusive answer on my basic question, which is:

Is it logically possible for me and a stranger to, today or "one of these days", set up a "smart contract" using nothing but Bitcoin Core, which has the following agreement:

  1. The smart contract starts when I have sent 1 BTC to the smart contract's BTC address and the other person has sent 300 WhateverCoins to the smart contract's WhateverCoin address.
  2. If none or either of us doesn't send the money within 24 hours, the contract is voided and the coins are returned to our wallets.
  3. Assuming that both sent the coins, the contract now activates.
  4. Until a specific date and time 30 days into the future, the contract will now run.
  5. For as long as the contract runs, a daily 10 WhateverCoins are sent to my WhateverCoin address (which was specified before the contract was created). This is my "interest" and the reason that I entered into the smart contract; to get money.
  6. Um... they can't... spend... my Bitcoin... but... they still somehow... want to enter into this agreement...

Alright. This is where it falls apart every time I try to ask this question, or construct it in my head. I basically don't see why they would enter into this agreement if they never get control of my 1 BTC, and I cannot possibly let them do that since it will then be lost as they will never return it. And if they are required to put 1 BTC as a safety deposit sum into the smart contract to get access to my 1 BTC, then what's the point of doing that in the first place? If they already have 1 BTC to use as security, they can just use that and skip the whole contract + interest!

I just don't see how this could ever work. It seems logically impossible. They must get control of my Bitcoin for it to be meaningful (?), but then I have to trust a stranger which is not going to happen. Only a complete idiot would do this. I'm not that idiot... anymore.

Is there some way to cryptographically ensure that I will get my 1 BTC back when the contract ends, no matter what, yet still giving the other person some kind of value/temporary ownership of the 1 BTC which is to be safely returned to me at the end of the contract? (Or a completely different Bitcoin, but the same value.)

Even if centralized services such as "BlockFi" didn't require KYC/AML stuff, I still could never trust them to have control of my coin. The stress from fearing that they will pull a "Mt. Gox" on me and exit-scam will not be made up for by the interest earned while it's there. Just because it's associated with "Winklevoss"/Gemini doesn't make me feel any safer. The most rich and famous people out there are often quite tricky and nasty. After all, the entire point of Bitcoin is to escape centralization. I don't understand how people can use and recommend centralized services which gain full control of your coins. It's impossible for a "true Bitcoin believer" to enter into such a contract.

Even if this is not possible right now, is there really anything which fundamentally prevents it from ever working? Is there really no "smart logic" which I'm overlooking that can be applied so that they get value from "owning" the coin, yet I am still guaranteed (not by a "pinkie promise"!) to get it back at the end of the time-based contract?

Of course, if somebody figures out a way to entirely break the entire Bitcoin blockchain/system, all is lost, but I mean assuming that Bitcoin keeps working as reliably as it has up until now.

I really need to make money, but I just cannot trust centralized entities or "promises" of any kind other than the cold logic found in a "smart contract".


Lots of things called "decentralized" or "defi" are scams, and I vigorously encourage you to stay away from them. Some of them are real, or useful, and have varying degrees of decentralization.

Still, nothing is ever going to give you interest if you don't give up custody of your coins. Interest is literally you being paid to take the risk of not being paid back. Without risk, there is no reason why anyone would ever pay you.

If you feel like there is a comparison with traditional finance, where it seems you get paid interest simply for leaving money on a bank account, please take into account that:

  • You give up custody to the bank, and the bank could go up in smoke, taking your money with them. If you keep your money hidden under your mattress (which is the equivalent of what you're asking for here, no matter how many smart contracts you hide it under), you don't get interest.
  • Often interest rates are lower than inflation, so you're really not getting anything for free (but obviously still more than just leaving it under your mattress).

If you want to see money grow, you'll need to invest it in something. Whether that's lending it out, or using it to build a business and seeing its value grow, or buying an asset with the intent of selling it back for more later (which is called speculation, and generally not considered investment). And inevitably, all of those things involve you taking the risk of not getting as much back as you put in.

This is not me encouraging you to do any of this. There is lot of garbage around in the cryptocurrency space, and you're entirely justified in not trusting much (or anything), but then also don't expect to get paid interest for it.

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