How to use the RSA key files generated by Crypto++ in java

Question

Hi - Good day to all :)
I have two RSA key files(private key file and public key file) generated by Crypto++ 5.2.1:
code here:
void GenerateRSAKey(unsigned int keyLength, const char *privFilename, const char *pubFilename, const char *seed)
     RandomPool randPool;
     randPool.Put((byte *)seed, strlen(seed));
     RSAES_OAEP_SHA_Decryptor priv(randPool, keyLength);
     HexEncoder privFile(new FileSink(privFilename));
     priv.DEREncode(privFile);
     privFile.MessageEnd();
     RSAES_OAEP_SHA_Encryptor pub(priv);
     HexEncoder pubFile(new FileSink(pubFilename));
     pub.DEREncode(pubFile);
     pubFile.MessageEnd();
}generated private key is:
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use this key in java
BufferedInputStream input=new BufferedInputStream(new FileInputStream("privateKey"));
          int size= input.available();
          byte[]buffer=new byte[size];
          input.read(buffer);
X509EncodedKeySpec lX509EncodedKeySpec = new X509EncodedKeySpec(buffer);
          PrivateKey lPrivateKey = KeyFactory.getInstance("RSA").generatePrivate(lX509EncodedKeySpec);there is a exception,at generatePrivate() method
at sun.security.rsa.RSAKeyFactory.generatePrivate(RSAKeyFactory.java:294)
     at sun.security.rsa.RSAKeyFactory.engineGeneratePrivate(RSAKeyFactory.java:171)
     at java.security.KeyFactory.generatePrivate(KeyFactory.java:322)
     at test.Main.main(Main.java:27)any body can help me?

Answer 1

X509 is for public keys, not private keys. You need PKCS8 using PKCS8EncodedKeySpec on the hex decoded private key string.
Your method for reading the private key from the file is flawed. The method available() does not guarantee to give you the file length. This is easy to prove since files can be longer than Integer.MAX_VALUE and available() returns an 'int'. To get the file length use File.length() which returns a 'long'. Also, reading from an InputStream using
input.read(buffer); does not guarantee to read all the bytes. For that you need to use something like DataInputStream.readFully().