@node-dlc/bitcoin/lib/Wif.ts

DLC bitcoin

import { Base58Check } from './Base58Check';

export type WifDecodeResult = {
  privateKey: Buffer;
  compressed: boolean;
  prefix: number;
};

export class Wif {
  /**
   * Encodes a private key using the WIF format. Can encode with compressed
   * or uncompressed format and can be for testnet or mainnet.
   *
   * Mainnet prefix: 0x80
   * Testnet prefix: 0xef
   *
   * Algorithm for WIF is:
   * 1. Start with the prefix
   * 2. Encode the secret in 32-byte big-endian format
   * 3. If the SEC format used for the public key address was compressed add
   *    a suffix of 0x01
   * 4. Combine wthe prefix from #1, serialized secret from #2, and suffix from #3
   * 5. Do hash256 of the result from #4 and get the first 4 bytes
   * 6. Take the combination of #4 and #5 and encode it with Base58
   *
   * @param privateKey a 32-byte private key as a big-endian buffer
   * @param compressed default of true
   * @param testnet default of false
   */
  public static encode(
    privateKey: Buffer,
    compressed = true,
    testnet = false,
  ): string {
    // 1. prefix
    const prefix = Buffer.from([testnet ? 0xef : 0x80]);

    // 2. encode as 32-byte big-endian number

    // 3. suffix
    const suffix = compressed ? Buffer.from([0x01]) : Buffer.alloc(0);

    // 4. combine 1, 2, and 3
    return Base58Check.encode(Buffer.concat([prefix, privateKey, suffix]));
  }

  /**
   * To decode a WIF value, we must first decode the base58check
   * input. If this validates then we need to split the resulting
   * buffer of data into two or three parts.
   *
   * The first byte is the prefix
   * The next 32-bytes are the private key
   *
   *
   * @param buf
   */
  public static decode(input: string): WifDecodeResult {
    const raw = Base58Check.decode(input);

    if (raw.length !== 33 && raw.length !== 34) {
      throw new Error('Invalid WIF encoding');
    }

    // prefix is the first byte
    const prefix = raw[0];

    // next 32-bytes are the private key
    const privateKey = raw.slice(1, 33);

    // check for compressed byte
    const compressed = raw.length === 34 && raw[33] === 0x01;

    // return our result object
    return { privateKey, compressed, prefix };
  }
}