Ethereum Riddle - https://github.com/JakeLin/ethereum-riddle

ethereum-riddle.js

const findPrivateKeyForAddress = (privateKeyStr, addressStr) => {
    if (typeof privateKeyStr !== 'string') {
        throw new TypeError('param privateKeyStr must be of String');
    } else if (typeof addressStr !== 'string') {
        throw new TypeError('param addressStr must be of String');
    }

    const hexStr = '0123456789abcdef'

    const targetAddress = Buffer.from(addressStr, 'hex')

    const privateKeyLength = privateKeyStr.length
    
    // Place the first blue stick from first to the second last of the hex
    for (let i = 0; i < privateKeyLength - 1; i++) {
        // Swap the first blue stick with a new hex (from `0` to `f`)
        for (const c1 of hexStr) {
            // Place the second red stick from one right of the placed blue stick the last of the hex
            for (let j = i + 1; j < privateKeyLength ; j++) {
                // Swap the second red stick with a new hex (from `0` to `f`)
                for (const c2 of hexStr) {
                    const privateKeyInChars = privateKeyStr.split('')
                    privateKeyInChars[i] = c1
                    privateKeyInChars[j] = c2
                    
                    // Generate the Ethereum address from the swapped private key
                    const privateKey = Buffer.from(privateKeyInChars.join(''), 'hex')
                    const address = getAddressFromPrivateKey(privateKey)
                    // Compare the generated address with the target address
                    if (address.equals(targetAddress)) {
                        // Bingo, we found it.
                        console.log('💥💥💥 PRIVATE KEY FOUND 💥💥💥')
                        return privateKey.toString('hex')
                    }
                }

            }
        }
    }
}