/**
* @param keyLength Block size of the asymmetric cipher, in bits. I thought I can get it from
* {@code asym.getBlockSize()} but that doesn't work with Sun's implementation.
*/
public CombinedCipherInputStream(InputStream in, Cipher asym, String algorithm, int keyLength)
throws IOException, GeneralSecurityException {
super(in);
String keyAlgorithm = getKeyAlgorithm(algorithm);
// first read the symmetric key cipher
byte[] symKeyBytes = new byte[keyLength / 8];
new DataInputStream(in).readFully(symKeyBytes);
SecretKey symKey = new SecretKeySpec(asym.doFinal(symKeyBytes), keyAlgorithm);
// the rest of the data will be decrypted by this symmetric cipher
Cipher sym = Secret.getCipher(algorithm);
sym.init(
Cipher.DECRYPT_MODE,
symKey,
keyAlgorithm.equals(algorithm) ? null : new IvParameterSpec(symKey.getEncoded()));
super.in = new CipherInputStream(in, sym);
}
public CombinedCipherOutputStream(OutputStream out, Cipher asym, String algorithm)
throws IOException, GeneralSecurityException {
super(out);
// create a new symmetric cipher key used for this stream
String keyAlgorithm = getKeyAlgorithm(algorithm);
SecretKey symKey = KeyGenerator.getInstance(keyAlgorithm).generateKey();
// place the symmetric key by encrypting it with asymmetric cipher
out.write(asym.doFinal(symKey.getEncoded()));
// the rest of the data will be encrypted by this symmetric cipher
Cipher sym = Secret.getCipher(algorithm);
sym.init(
Cipher.ENCRYPT_MODE,
symKey,
keyAlgorithm.equals(algorithm) ? null : new IvParameterSpec(symKey.getEncoded()));
super.out = new CipherOutputStream(out, sym);
}