Crypto.java

package aQute.libg.cryptography;

import java.math.BigInteger;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.Signature;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.RSAPublicKeySpec;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Crypto {
	static final Pattern	RSA_PRIVATE	= Pattern.compile("\\s*RSA\\.Private\\((\\p{XDigit})+:(\\p{XDigit})+\\)\\s*");
	static final Pattern	RSA_PUBLIC	= Pattern.compile("\\s*RSA\\.Public\\((\\p{XDigit})+:(\\p{XDigit})+\\)\\s*");

	/**
	 * @param <T>
	 * @param spec
	 * @return key
	 * @throws Exception
	 */
	@SuppressWarnings("unchecked")
	public static <T> T fromString(String spec, Class<T> c) throws Exception {
		if (PrivateKey.class.isAssignableFrom(c)) {
			Matcher m = RSA_PRIVATE.matcher(spec);
			if (m.matches()) {
				return (T) RSA.createPrivate(new BigInteger(m.group(1)), new BigInteger(m.group(2)));
			}
			throw new IllegalArgumentException("No such private key " + spec);
		}

		if (PublicKey.class.isAssignableFrom(c)) {
			Matcher m = RSA_PUBLIC.matcher(spec);
			if (m.matches()) {
				return (T) RSA.create(new RSAPublicKeySpec(new BigInteger(m.group(1)), new BigInteger(m.group(2))));
			}
			throw new IllegalArgumentException("No such public key " + spec);
		}
		return null;
	}

	public static String toString(Object key) {
		if (key instanceof RSAPrivateKey) {
			RSAPrivateKey pk = (RSAPrivateKey) key;
			return "RSA.Private(" + pk.getModulus() + ":" + pk.getPrivateExponent() + ")";
		}
		if (key instanceof RSAPublicKey) {
			RSAPublicKey pk = (RSAPublicKey) key;
			return "RSA.Private(" + pk.getModulus() + ":" + pk.getPublicExponent() + ")";
		}
		return null;
	}

	// public static <T extends Digest> Signer<T> signer(PrivateKey key,
	// Digester<T> digester) throws NoSuchAlgorithmException {
	// Signature s = Signature.getInstance(key.getAlgorithm() + "with" +
	// digester.getAlgorithm());
	// return new Signer<T>(s,digester);
	// }

	public static Verifier verifier(PublicKey key, Digest digest) throws NoSuchAlgorithmException {
		Signature s = Signature.getInstance(key.getAlgorithm() + "with" + digest.getAlgorithm());
		return new Verifier(s, digest);
	}

}