problem reading a publickey file and use the key to encrypt another file

I've been strugling with reading a publickey file which I want to get the key sting in the file and use it to encrypt another file. I'm using RSA PKCS1 v1.5 in encrypting and signing the file with SH1 hashing algorythim but thats not the problem, the problem is that I've been supplied with the publickey file to use when encrypting and I cant seem to win with reading the file and generating a publicKey object.

Here's the code:

void setPublicKey(String file) 
{ 
     try 
     { 
       File开发者_JAVA技巧InputStream keyfis = new FileInputStream(file); 
       byte[] encKey = new byte[keyfis.available()]; keyfis.read(encKey);
       keyfis.close();
       X509EncodedKeySpec pubKeySpec = new X509EncodedKeySpec(encKey);
       KeyFactory keyFactory = KeyFactory.getInstance("RSA");
// I get an exception on the below line
       publicKey = keyFactory.generatePublic(pubKeySpec);
     } catch (Exception e)
       {
         e.printStackTrace();
       }
}

Can someone please help!!

---

AFAIK X509 encoded keys are binary files encoded using ASN.1. Therefore the question on new-lines at the end does not make any sense.

If you have a text file you have a PEM encoded file and I am currently not sure which KeySpec you have to use in this case.

You may convert the PEM encoded key to a DER encoded key (e.g. using OpenSSL) or you can use BouncyCastle which as support for loading PEM encoded keys.

BTW: Using keyfis.read(encKey); is dangerous as the read method only reads up encKey bytes but don't have to. Better create a DataInputStream from the InputStream and use readFully(encKey):

new DataInputStream(keyfis).readFully(encKey);

---

Found the solution but not sure yet if its the right solution coz I still have to get the PrivateKey and decrypt the file but for now I was able to encrypt it using the supplied PublicKey as the modulus but I don’t have the exponent and I just used some common number “65537” as the exponent Which I read that it is not a critical part of the encryption.

I had to change the logic to use the RSAPublicKeySpec (which uses BigInteger and Base64Decoder)instead of X509EncodedKeySpec to set the KeySpec And continue to use the KeyFactory object to generate the public key. Now this logic NEEDS the modulus and exponent.

byte[] buffer = new byte[(int) new File(file).length()];
BufferedInputStream f = new BufferedInputStream(new FileInputStream(file));
f.read(buffer);
String modulusBase64 = new String(buffer);
BASE64Decoder b64dec = new BASE64Decoder();
String exponentBase64 = "65537";
RSAPublicKeySpec publicKeySpec = new RSAPublicKeySpec(new BigInteger    (1,                      b64dec.decodeBuffer(modulusBase64)), new BigInteger(1,     b64dec.decodeBuffer(exponentBase64)));
KeyFactory publicKeyFactory = KeyFactory.getInstance("RSA");
publicKey = publicKeyFactory.generatePublic(publicKeySpec);

//This is the PublicKey in the file. "J45t4SWGbFzeNuunHliNDZcLVeFU7lOpyNkX1xX+sVNaVJK8Cr0rSjUkDC8h9n+Zg7m0MVYk0byafPycmzWNDynpvj2go9mXwmUpmcQprX1vexxT5j1XmAaBZFYaJRcPWSVU92pdNh1Sd3USdFjgH0LQ5B3s8F95xdyc/5I5LDKhRobx6c1gUs/rnJfJjAgynrE4AsNsNem+STaZWjeb4J+f5Egy9xTSEl6UWxCClgCwhXopy10cBlH8CucpP0cyckOCIOloJ7mEMRCIpp6HPpYexVmXXSikTXh7aQ7tSlTMwUziIERc/zRpyj1Nk96Y7V8AorLFrn1R4Of66mpAdQ=="