区块链开发之生成12个助记词

时间:2018-07-30作者:klpeng分类:IT综合浏览:14719评论:0

我最近封装了一个库,使用起来更简单,大家可以移步这里:Bip44确定性算法的android实现
Java版的库:Bip44确定性算法的Java实现库(Android和java平台都可以使用)

这里添加一下SecureRandomUtils类的代码,
注:如果你引入了web3j的库,就不需要自己在项目中添加此类,手动添加此类,里面的LinuxSecureRandom类,可以使用bitcoinj库下的,具体路径为:org.bitcoinj.crypto.LinuxSecureRandom

这里使用bitcoinj库,来实现生成bip39的12个助记词,引用库

implementation ‘org.bitcoinj:bitcoinj-core:0.14.7’

填坑1

如果你直接引用库之后,直接安装运行apk,会造成app崩溃,这是因为这个库里面有一个libscrypt.dylib,这个库是针对x86_64平台的,并且没有其他平台的这个库,所以在arm cpu平台的手机app会崩溃,解决方案就是在gradle的android节点下,加上以下配置

 packagingOptions {
        exclude 'lib/x86_64/darwin/libscrypt.dylib'
        exclude 'com/google/thirdparty/publicsuffix/PublicSuffixPatterns.gwt.xml'
        exclude 'com/google/thirdparty/publicsuffix/PublicSuffixType.gwt.xml'
        exclude 'org/bitcoinj/crypto/mnemonic/wordlist/english.txt'
        exclude 'org/bitcoinj/crypto/cacerts'
    }

填坑2

我们要得到12个随机的单词,就要用到里面的MnemonicCode类,但是这个类,默认会new一个实例出来,并且默认加载的单词库路径方式是不支持android的,官方代码如下

   static {
        try {
            INSTANCE = new MnemonicCode();
        } catch (FileNotFoundException e) {
            // We expect failure on Android. The developer has to set INSTANCE themselves.
            if (!Utils.isAndroidRuntime())
                log.error("Could not find word list", e);
        } catch (IOException e) {
            log.error("Failed to load word list", e);
        }
    }
 /** Initialise from the included word list. Won't work on Android. */
    public MnemonicCode() throws IOException {
        this(openDefaultWords(), BIP39_ENGLISH_SHA256);
    }

    private static InputStream openDefaultWords() throws IOException {
        InputStream stream = MnemonicCode.class.getResourceAsStream(BIP39_ENGLISH_RESOURCE_NAME);
        if (stream == null)
            throw new FileNotFoundException(BIP39_ENGLISH_RESOURCE_NAME);
        return stream;
    }

可以从代码中看出来,在android平台此路径是绝对不可用的,所以我们要手动自己new这个对象,使用public MnemonicCode(InputStream wordstream, String wordListDigest) throws IOException, IllegalArgumentException这个构造函数

具体实现代码

    public static void generateMnemonic(Context context) throws Exception {
        MnemonicCode mnemonicCode = new MnemonicCode(context.getAssets().open("english.txt"), null);

        SecureRandom secureRandom = SecureRandomUtils.secureRandom();
        byte[] initialEntropy = new byte[16];//算法需要,必须是被4整除
        secureRandom.nextBytes(initialEntropy);
        List<String> wd = mnemonicCode.toMnemonic(initialEntropy);
        if (wd == null || wd.size() != 12)
            throw new RuntimeException("generate word error");
        else {
            words.clear();
            words.addAll(wd);
            LogUtils.d(words.toString());
        }
    }

SecureRandomUtils工具类



import java.security.SecureRandom;

/**
 * 如果你引入了web3j的库,就不需要自己在项目中添加此类,手动添加此类,里面的LinuxSecureRandom类,可以使用bitcoinj库下的,具体路径为:org.bitcoinj.crypto.LinuxSecureRandom
 * Utility class for working with SecureRandom implementation.
 *
 * <p>This is to address issues with SecureRandom on Android. For more information, refer to the
 * following <a href="https://github.com/web3j/web3j/issues/146">issue</a>.
 */
final public class SecureRandomUtils {

    private static final SecureRandom SECURE_RANDOM;

    static {
        if (isAndroidRuntime()) {
            new LinuxSecureRandom();
        }
        SECURE_RANDOM = new SecureRandom();
    }

    public static SecureRandom secureRandom() {
        return SECURE_RANDOM;
    }

    // Taken from BitcoinJ implementation
    // https://github.com/bitcoinj/bitcoinj/blob/3cb1f6c6c589f84fe6e1fb56bf26d94cccc85429/core/src/main/java/org/bitcoinj/core/Utils.java#L573
    private static int isAndroid = -1;

    static boolean isAndroidRuntime() {
        if (isAndroid == -1) {
            final String runtime = System.getProperty("java.runtime.name");
            isAndroid = (runtime != null && runtime.equals("Android Runtime")) ? 1 : 0;
        }
        return isAndroid == 1;
    }

    private SecureRandomUtils() { }
}

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