# BitVM and sCrypt

> original: <https://gist.github.com/msinkec/5827d5285a18de8930324f67b880841e>&#x20;

#### Invitation to Bitcoin Developers: Utilize sCrypt for Advanced BitVM Implementations

**To the Bitcoin Development Community,**

In light of the recent advancements in BTC's computational capabilities introduced by [BitVM](https://bitvm.org/bitvm.pdf), we are extending an open invitation to explore the integration of sCrypt as a language for developing BitVM scripts. BitVM represents a significant advancement in Bitcoin's scripting capabilities, enabling Turing-complete contracts within the existing BTC framework.

**Technical Overview:**

BitVM facilitates off-chain computation, essential for complex contract execution while maintaining Bitcoin's on-chain efficiency. While Assembly (ASM) scripts are so far used to express contracts for BitVM, they present certain limitations in terms of readability and broader accessibility.

[sCrypt](https://scrypt.io/), a high-level language based on TypeScript tailored for Bitcoin smart contracts, offers a more efficient and streamlined approach for developers. The language's design aligns with traditional programming paradigms, enhancing understandability and maintainability of scripts.

**Example of Gate Commitment in sCrypt:**

```
type HashPair = {
    hash0: Ripemd160
    hash1: Ripemd160
}

export class DemoBitVM extends SmartContract {
    @prop()
    hashPairA: HashPair

    @prop()
    hashPairB: HashPair

    @prop()
    hashPairE: HashPair

    constructor(
        hashPairA: HashPair,
        hashPairB: HashPair,
        hashPairE: HashPair,
    ) {
        super(...arguments)
        this.hashPairA = hashPairA
        this.hashPairB = hashPairB
        this.hashPairE = hashPairE
    }

    @method()
    public openGateCommit(
        preimageA: ByteString,
        preimageB: ByteString,
        preimageE: ByteString,
    ) {
        const bitA = this.bitValueCommit(this.hashPairA, preimageA)
        const bitB = this.bitValueCommit(this.hashPairB, preimageB)
        const bitE = this.bitValueCommit(this.hashPairE, preimageE)
        assert(this.nand(bitA, bitB) == bitE)
    }

    @method()
    bitValueCommit(hashPair: HashPair, preimage: ByteString): boolean {
        const h = hash160(preimage)
        assert (h == hashPair.hash0 || h == hashPair.hash1)
        return h == hashPair.hash1
    }

    @method()
    nand(A: boolean, B: boolean): boolean {
        return !(A && B)
    }

}
```

The code above represents a simple gate commitment for BitVM. It has a single entry point, i.e. the public function "openGateCommit", which can be unlocked by providing the apporpriate hash preimages of the commitments.

The code compiles into a bitcoin script, the function of which is analogous to the script described in the BitVM whitepaper (Figure 2):

```
// Reveal Preimage of hashE0 or hashE1
<hashE0/1>
OP_BITCOMMITMENT
OP_TOALTSTACK
// Now the bit value of "E" is on the stack
// Reveal Preimage of hashB0 or hashB1
<hashB0/1>
OP_BITCOMMITMENT
OP_TOALTSTACK
// Now the bit value of "B" is on the stack
// Reveal Preimage of hashA0 or hashA1
<hashA0/1>
OP_BITCOMMITMENT
OP_TOALTSTACK
// Now the bit value of "A" is on the stack
//
// Verify that "A NAND B == E"
//
// Read "B" from alt stack
OP_FROMALTSTACK
// Compute A NAND B
OP_NAND
// Read "E" from alt stack
OP_FROMALTSTACK
// Check A NAND B == E
OP_EQUALVERIFY
```

The equivalent is expressed in sCrypt as:

```
const bitA = this.bitValueCommit(this.hashPairA, preimageA)
const bitB = this.bitValueCommit(this.hashPairB, preimageB)
const bitE = this.bitValueCommit(this.hashPairE, preimageE)
assert(this.nand(bitA, bitB) == bitE)
```

For more information about sCrypt, please refer to [the official documentation](https://docs.scrypt.io/).

**Invitation and Objectives:**

1. **Examination of sCrypt**: We encourage the exploration of sCrypt's features and syntax. Its alignment with conventional programming languages positions it as a viable candidate for BitVM script development.
2. **Contribution Using sCrypt**: Contributions in sCrypt to the BitVM ecosystem are highly encouraged. Such endeavors would ease the utilization of BTC's full scripting capabilities.
3. **Technical Exchange and Collaboration**: The advancement of BitVM and sCrypt requires collective efforts in knowledge exchange and technical collaboration. We welcome insights from both experienced and emerging developers in the Bitcoin community.

**Sincerely,**

Mihael Šinkec, sCrypt Inc.


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