HD wallet具有管理多个密钥和地址的机制，我们可以使用一个随机字符串seed通过BIP32或BIP44协议创建一个HD wallet，但是一串字符串的记忆成本太高，而且摘抄下来也会很麻烦。所以BIP39协议应运而生，他是可以使用12-24单字（可以是英文、中文、日文等等语言）来帮助用户更好的保存seed。一般我们使用长度为12个的英文单词来生成BIP39的内容，这串单词被称为mnemonic code，中文名叫助记词。
BIP-39 生成助记词流程
助记词钱包是通过BIP-39中定义的标准化过程自动生成的，钱包从熵源开始，增加校验和，然后将熵映射到字典列表中。
1.创建一个128-256位的随机序列（熵）
2.提出SHA256哈希的前几位（熵长/32）,就可以创建一个随机序列的校验和。
3.将校验和添加到随机序列的末尾。
4.将序列划分为包含11位的不同部分。
5.将每个包含11位部分的值与一个预先定义的2048个单词的字典做对应。
6.生成的有顺序的单词组就是助记词。
新建项目
导入CryptoSwift库
- 新建
BIP39.swift文件
import Foundation
import CryptoSwift
public enum BIP39Language {
case english
case chinese_simplified
case chinese_traditional
case japanese
case korean
case french
case italian
case spanish
var words: [String] {
switch self {
case .english:
return englishWords
case .chinese_simplified:
return simplifiedchineseWords
case .chinese_traditional:
return traditionalchineseWords
case .japanese:
return japaneseWords
case .korean:
return koreanWords
case.french:
return frenchWords
case .italian:
return italianWords
case .spanish:
return spanishWords
}
}
var separator: String {
switch self {
case .japanese:
return "\u{3000}"
default:
return " "
}
}
}
public class BIP39 {
/// 返回一组助记词
static public func generateMnemonics(bitsOfEntropy: Int, language: BIP39Language = BIP39Language.english) throws -> String? {
// 1.创建一个128-256位的随机序列（熵）
guard bitsOfEntropy >= 128 && bitsOfEntropy <= 256 && bitsOfEntropy % 32 == 0 else {return nil}
guard let entropy = Data.randomBytes(length: bitsOfEntropy/8) else {throw AbstractError.noEntropyError}
return BIP39.generateMnemonicsFromEntropy(entropy: entropy, language: language)
}
/// 通过熵生成助记词
static public func generateMnemonicsFromEntropy(entropy: Data, language: BIP39Language = BIP39Language.english) -> String? {
guard entropy.count >= 16, entropy.count & 4 == 0 else {return nil}
// 2.提出SHA256哈希的前几位（熵长/32）,就可以创建一个随机序列的校验和。
let checksum = entropy.sha256()
// 3.将校验和添加到随机序列的末尾。
let checksumBits = entropy.count*8/32
var fullEntropy = Data()
fullEntropy.append(entropy)
fullEntropy.append(checksum[0 ..< (checksumBits+7)/8 ])
var wordList = [String]()
// 4.将序列划分为包含11位的不同部分
for i in 0 ..< fullEntropy.count*8/11 {
guard let bits = fullEntropy.bitsInRange(i*11, 11) else {return nil}
let index = Int(bits)
guard language.words.count > index else {return nil}
// 5.将每个包含11位部分的值与一个预先定义的2048个单词的字典做对应。
let word = language.words[index]
wordList.append(word)
}
let separator = language.separator
// 6.生成的有顺序的单词组就是助记词。
return wordList.joined(separator: separator)
}
/// 通过助记词返回一个熵
static public func mnemonicsToEntropy(_ mnemonics: String, language: BIP39Language = BIP39Language.english) -> Data? {
let wordList = mnemonics.components(separatedBy: " ")
guard wordList.count >= 12 && wordList.count % 4 == 0 else {return nil}
var bitString = ""
for word in wordList {
let idx = language.words.index(of: word)
if (idx == nil) {
return nil
}
let idxAsInt = language.words.startIndex.distance(to: idx!)
let stringForm = String(UInt16(idxAsInt), radix: 2).leftPadding(toLength: 11, withPad: "0")
bitString.append(stringForm)
}
let stringCount = bitString.count
if stringCount % 33 != 0 {
return nil
}
let entropyBits = bitString[0 ..< (bitString.count - bitString.count/33)]
let checksumBits = bitString[(bitString.count - bitString.count/33) ..< bitString.count]
guard let entropy = entropyBits.interpretAsBinaryData() else {
return nil
}
let checksum = String(entropy.sha256().bitsInRange(0, checksumBits.count)!, radix: 2).leftPadding(toLength: checksumBits.count, withPad: "0")
if checksum != checksumBits {
return nil
}
return entropy
}
/// 通过助记词返回一个seed（种子）
static public func seedFromMmemonics(_ mnemonics: String, password: String = "", language: BIP39Language = BIP39Language.english) -> Data? {
let valid = BIP39.mnemonicsToEntropy(mnemonics, language: language) != nil
if (!valid) {
print("Potentially invalid mnemonics")
}
guard let mnemData = mnemonics.decomposedStringWithCompatibilityMapping.data(using: .utf8) else {return nil}
let salt = "mnemonic" + password
guard let saltData = salt.decomposedStringWithCompatibilityMapping.data(using: .utf8) else {return nil}
guard let seedArray = try? PKCS5.PBKDF2(password: mnemData.bytes, salt: saltData.bytes, iterations: 2048, keyLength: 64, variant: HMAC.Variant.sha512).calculate() else {return nil}
let seed = Data(bytes:seedArray)
return seed
}
}
- 统一错误处理类
AbstractError.swift
import Foundation
public enum AbstractError: Error {
case noEntropyError
case keyDerivationError
case aesError
case invalidAccountError
case invalidPasswordError
case encryptionError(String)
}
项目结构
image.png
demo使用：
// 生成助记词
let mnemonic = try! BIP39.generateMnemonics(bitsOfEntropy: 128)!
// 种子
let seed = BIP39.seedFromMmemonics(mnemonic)
print("助记词：\(mnemonic)")
print("种子seed：\(seed?.toHexString() ?? "")")
示例结果
助记词：soldier stay tackle return tackle lens praise leader traffic sword anxiety intact
种子seed：bc428e06a1bc08b3bf52ce6b1fd1a295518888b1de10eea3231043bed07e4ccd108e5a192bfd073d3db81dba8311ed2b109fbda3d6daa63d27000e395a46f887
验证地址：
https://iancoleman.io/bip39/
demo下载地址：
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