在J2ME中如何将字符串转换为SHA-256哈希？

Question

            String[] stringArray = (String[]) dotREZApi.getCurrentRequest().getResponseHeaders().get("X-Session-Id");
            String tmpSessionId = stringArray[0];

            byte[] input = null;
            try {
                input = new String("X-Session-Sig" + tmpSessionId + "test").getBytes("UTF-8"); // String that will be converted
            } catch (UnsupportedEncodingException e) {
                // TODO Auto-generated catch block
                System.out.println("Unsupported encoding exception");
                e.printStackTrace();
            }

            // trying to create a key, i don't know if this is right I just did this because I needed a key             
            byte[] key = new byte[4];
            int tmpInt = new Random().nextInt();
            key[0] = (byte)(tmpInt >> 24);
            key[1] = (byte)(tmpInt >> 16);
            key[2] = (byte)(tmpInt >> 8);
            key[3] = (byte)(tmpInt);


            Digest digest = new SHA256Digest();
            HMac hmac = new HMac(digest);

            hmac.init(new KeyParameter(key)); // maybe this is the problem? the documentaiton never states where do I get this key or how to generate it
            hmac.update(input, 0, input.length);
            byte[] output = new byte[digest.getDigestSize()];
            hmac.doFinal(output, 0);
            dotREZApi.setSessionSig(new String(Hex.encode(output)));

行input=new String（“x-session-sig”+tmpSessionId+“test”）.getbytes（“utf-8”）；是我构造字符串并将其转换为byte[]以转换为SHA-256散列的地方，其中tmpSessionId是我从HTTP请求中获取的值。产生的散列将在以后的请求中发送。

Answer 1

最后我没有使用BouncyCastle。

我最终使用了来自J2ME的MessageDigest，虽然它没有相同的方法可用，但我可以让它工作：

    byte[] input = null;
    try {
        input = new String("X-Session-Id" + tmpSessionId + "test").getBytes("UTF-8");
    } catch (UnsupportedEncodingException e) {
        // TODO Auto-generated catch block
        System.out.println("Unsupported encoding exception");
        e.printStackTrace();
    }

    MessageDigest messageDigest;
    byte[] output = new byte[32]; // since SHA256 hash is 256 bits = 32 bytes
    try {
        messageDigest = MessageDigest.getInstance("SHA-256");
        messageDigest.update(input, 0, input.length);
        messageDigest.digest(output, 0, 32); // same
    } catch (NoSuchAlgorithmException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (DigestException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

我希望这种BouncyCastle的替代方案也适用于其他人。