AliasFromFingerprintGenerator.java

package won.cryptography.ssl;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;

/**
 * User: ypanchenko
 * Date: 19.10.2015
 */
public class AliasFromFingerprintGenerator implements AliasGenerator
{
  public AliasFromFingerprintGenerator() {
  }

  @Override
  public String generateAlias(final X509Certificate certificate) throws CertificateException {
    String fingerprint = null;
    try {
      fingerprint = digest(certificate.getPublicKey().getEncoded());
    } catch (Exception e) {
      new CertificateException("Alias generation from certificate fingerprint failed", e);
    }
    return fingerprint;
  }

  public String digest(final byte[] data) throws NoSuchAlgorithmException {
    MessageDigest md = MessageDigest.getInstance("SHA3-224");
    byte[] hash = md.digest(data);
    StringBuffer hexString = new StringBuffer();
    for (int i = 0; i < hash.length; i++) {
      String hex = Integer.toHexString(0xff & hash[i]);
      if(hex.length() == 1) hexString.append('0');
      hexString.append(hex);
    }
    return hexString.toString();
  }

  public static void main (String... args) throws Exception{
    System.out.println("digest:" + new AliasFromFingerprintGenerator().digest("digest".getBytes()));
  }
}