Can org.bouncycastle.openssl.PEMReader read java.security.PrivateKey?

Question

I have following code:

PrivateKey key = null;
X509Certificate cert = null;
KeyPair keyPair = null;

final Reader reader = new StringReader(pem);
try {
    final PEMReader pemReader = new PEMReader(reader, new PasswordFinder() {
        @Override
        public char[] getPassword() {
            return password == null ? null : password.toCharArray();
        }
    });

    Object obj;
    while ((obj = pemReader.readObject()) != null) {
        if (obj instanceof X509Certificate) {
            cert = (X509Certificate) obj;
        } else if (obj instanceof PrivateKey) {
            key = (PrivateKey) obj;
        } else if (obj instanceof KeyPair) {
            keyPair = (KeyPair) obj;
        }
    }
} finally {
    reader.close();
}

Will it ever read PrivateKey? In other words, can any PEM file contain pure private key only? If yes, could you provide me a sample PEM file?

Thanks in advace.

I don't have a sample at hand but as you can read here: http://ospkibook.sourceforge.net/docs/OSPKI-2.4.7/OSPKI-html/sample-priv-key.htm it's possible. (or is this an attempt to get private-keys from people :)) — albertjan, Nov 24 '11 at 20:21
See also *[Formatting RSA keys for OpenSSL in Java](http://stackoverflow.com/q/3660132/3474).* — erickson, Nov 24 '11 at 21:14

score 7 · Answer 1 · edited May 23 '17 at 10:08

A file can contain only a private key, and it can be encrypted or clear text. OpenSSL does this all the time.

I reviewed the code for PEMReader, however, and it looks like it will return a KeyPair from an RSA private key (the private key file contains all the necessary information for the corresponding public key). It looks like it will never return simply a PrivateKey from readObject().

Here's an unencrypted 1024 RSA private key from OpenSSL.

Here's the corresponding public key:

A KeyStore is meant to be used to carry public, private, and symmetric keys in a Java application. Most Java applications store private keys in a PKCS #8 encoding (which is not the same as the OpenSSL format), and public keys are represented with a SubjectPublicKeyInfo structure (which is the same as OpenSSL).

Thanks for answer. Your sample of private key contains also public key and therefore it is a KeyPair. You can extract a public key with: openssl pkey -inform PEM -pubout -outform PEM. I was wondering if there can be a PEM with just a pure private key, with no information about public key. — Martin Ždila, Nov 25 '11 at 09:16
@Martin Actually, what my sample contains is an `RSAPrivateKey`, as defined PKCS #1. As I stated, it *does* contain the public exponent (along with the Chinese Remainder Theorem values), to facilitate recovery of the public key. Any private key that can be read by `PEMReader` (or the OpenSSL utilities) must be in this standard format, although this can be enclosed in a PKCS #8 or PEM wrapper. Some implementations of SSH2 are unusual in that they don't use a PKCS #1 key. PEMReader will **never** return a `PrivateKey`; it will raise an exception if a private key is not in PKCS #1 format. — erickson, Nov 25 '11 at 16:43

Can org.bouncycastle.openssl.PEMReader read java.security.PrivateKey?

1 Answers1