readprivatekey.java

public static PGPSecretKey readSecretKey(InputStream input)	throws IOException, PGPException {
	PGPSecretKeyRingCollection pgpSec = new PGPSecretKeyRingCollection(
		PGPUtil.getDecoderStream(input));

	Iterator keyRingIter = pgpSec.getKeyRings();
	while (keyRingIter.hasNext()) {
		PGPSecretKeyRing keyRing = (PGPSecretKeyRing) keyRingIter.next();

		Iterator keyIter = keyRing.getSecretKeys();
		while (keyIter.hasNext()) {
			PGPSecretKey key = (PGPSecretKey) keyIter.next();

			if (key.isSigningKey()) {
				return key;
			}
		}
	}

	throw new IllegalArgumentException(
		"Can't find signing key in key ring.");
}