Sophi

A simple language for Bitcoin non-custodial smart contracts.

Sophi has no runtime, no blockchain execution, and no custody of funds. You describe what a fair exchange looks like — and Sophi proves it is mathematically valid.

Install

pip install sophi

Write a swap

Describe who has what before, and who has what after:

swap {
  before:
    alice = 0.5 BTC
    bob = 50000 USDT

  after:
    alice = 50000 USDT
    bob = 0.5 BTC
}

Run:

sophi compile trade.sph

Sophi verifies: BTC before == BTC after, USDT before == USDT after. If the math holds, it produces a valid proof. If not, clear error.

Transfer syntax

Same swap, different style:

swap {
  transfer 0.5 BTC from alice to bob
  transfer 50000 USDT from bob to alice
}

Three or more participants

swap {
  transfer 0.5 BTC from alice to carol
  transfer 50000 USDT from bob to alice
  transfer 1 ETH from carol to bob
}

Any number of participants. All verified atomically.

What the proof looks like

{
  "swap_id": "f970dc4b...",
  "status": "valid",
  "conservation": {
    "BTC":  { "before": "0.5",   "after": "0.5"   },
    "USDT": { "before": "50000", "after": "50000"  }
  },
  "delta": {
    "alice": { "BTC": "-0.5",  "USDT": "+50000" },
    "bob":   { "BTC": "+0.5",  "USDT": "-50000" }
  },
  "htlc": {
    "secret_hash": "a3f8c2...",
    "timeout_blocks": 144,
    "legs": [
      { "from": "alice", "to": "bob",   "asset": "BTC",  "amount": "0.5"   },
      { "from": "bob",   "to": "alice", "asset": "USDT", "amount": "50000" }
    ]
  }
}

Signatures are external

The .sph file never contains signatures or private keys. After compiling, each party signs the swap_id using their own Bitcoin wallet:

{
  "swap_id": "f970dc4b...",
  "signatures": {
    "alice": { "address": "bc1qalice...", "signature": "H7f8c2..." },
    "bob":   { "address": "bc1qbob...",   "signature": "K9d3e1..." }
  }
}

Then verify:

from sophi import compile_source, verify_proof

compiled = compile_source(open("trade.sph").read())
result = verify_proof(compiled, proof_json)
# result["status"] == "signatures_valid"

Rules that never change

• 1 BTC is never equal to 1 USDT — each asset verified separately
• No value is ever created or destroyed
• Funds never leave the participants control
• No on-chain execution — Sophi only verifies, never executes

License

Business Source License 1.1 — converts to Apache 2.0 after 4 years.