Java 如何使用android获取摘要？

我需要签署一个

字符串

，然后将两者都发送出去。我有一个

.pem

文件作为私钥，我正在尝试将此文件转换为

私钥

这是我的代码：

try {
            File privateKeyFile = new File("path to .pem file");

            //TODO: HOW CAN I CONVERT THAT FILE INTO PRIVATE KEY?

            Signature signature = Signature.getInstance("SHA1withRSA");
            signature.initSign(privateKey);
            signature.update(data.getBytes());

            byte[] sign = signature.sign();
        } catch (NoSuchAlgorithmException | SignatureException e) {
            e.printStackTrace();
        }

public String signData(final String data, final String privateKeyString) throws NoSuchAlgorithmException, InvalidKeySpecException, InvalidKeyException, SignatureException {

        X509EncodedKeySpec keySpec = new X509EncodedKeySpec(privateKeyString.getBytes());
        KeyFactory keyFactory = KeyFactory.getInstance("RSA");
        PrivateKey privateKey = keyFactory.generatePrivate(keySpec);


        Signature signature = Signature.getInstance("SHA256withRSA");
        signature.initSign(privateKey);
        signature.update(data.getBytes());
        byte[] sign = signature.sign();
        return new String(sign);
    }

你对此有什么建议吗？

我这样解决： 取而代之的是使用

.pem

文件，我直接保存了从

PrivateKey

获取的

字符串

，然后当我需要对数据签名时，我得到该

字符串

，并将其转换为

PrivateKey

这是我的代码：

try {
            File privateKeyFile = new File("path to .pem file");

            //TODO: HOW CAN I CONVERT THAT FILE INTO PRIVATE KEY?

            Signature signature = Signature.getInstance("SHA1withRSA");
            signature.initSign(privateKey);
            signature.update(data.getBytes());

            byte[] sign = signature.sign();
        } catch (NoSuchAlgorithmException | SignatureException e) {
            e.printStackTrace();
        }

public String signData(final String data, final String privateKeyString) throws NoSuchAlgorithmException, InvalidKeySpecException, InvalidKeyException, SignatureException {

        X509EncodedKeySpec keySpec = new X509EncodedKeySpec(privateKeyString.getBytes());
        KeyFactory keyFactory = KeyFactory.getInstance("RSA");
        PrivateKey privateKey = keyFactory.generatePrivate(keySpec);


        Signature signature = Signature.getInstance("SHA256withRSA");
        signature.initSign(privateKey);
        signature.update(data.getBytes());
        byte[] sign = signature.sign();
        return new String(sign);
    }